CN104574492A - Real-time rendering method and device for object composed of multiple layers of materials - Google Patents

Abstract

The invention provides a real-time rendering method and device for an object composed of multiple layers of materials. The real-time rendering method for the object composed of the multiple layers of materials comprises the steps that firstly, a secondary surface BRDF of the base material layer of the multi-layer object is calculated according to the first optical property information of the multi-layer object, and then a secondary surface BRDF of the base material layer of the multi-layer object is calculated after a material layer is added to the base material layer; secondly, a third BRDF is calculated according to the second optical property information of the material layer which is finally added; finally, real-time rendering of the object composed of the multiple layers of materials is conducted based on the second BRDF and the third BRDF. Due to the fact that the secondary surface BRDFs of the object are calculated in an iterated mode after all the material layers are added, the process of simulating the spreading of light in the object required when the secondary surface BRDFs are calculated according to existing algorithms such as the light tracking algorithm is effectively avoided, in this way, the complexity of the algorithm for calculating the secondary surface BRDFs of the object composed of the multiple layers of materials is greatly reduced, and calculating time is shortened.

Description

The real-time rendering method and apparatus of multi-layer material object

Technical field

The present invention relates to computer graphical Rendering field, particularly relate to a kind of real-time rendering method and apparatus of multi-layer material object.

Background technology

The important application of computer graphical in the industry one is " Virtual prototype ", the i.e. design process fully digitalization of industrial products (as: automobile), the decision-making of design is mainly based on " Virtual prototype " of Practical computer teaching, obviously, rendering image and real industrial products are only had enough close to the needs that could meet design decision.

In computer graphics, usual use bidirectional reflectance distribution function (BidirectionalReflectance Distribution Function, BRDF) describe the reflection characteristic of body surface, the lifting of high-quality BRDF to rendered picture plays very important effect.BRDF can be superposed by two parts and form: surperficial BRDF (surface BRDF) and subsurface BRDF (subsurface BRDF).Surface BRDF is after light is irradiated to body surface, through the reflected light distribution that body surface reflects to form.Subsurface BRDF is that light enters interior of articles by body surface, again from body surface reflected light distribution out after scattering.At present, many industrial products can use layered coating to reach better sensory effects, and as automobile, the spraying paint of furniture, the high realism effect playing up these products of simulation just needs is carried out modeling to every coating and is merged into the final BRDF of its correspondence.Wherein, calculating high-quality subsurface BRDF is exactly an indispensable important ring.The algorithm of conventional calculating high-quality subsurface BRDF has Ray Tracing Algorithm, Discrete Ordinate Methods algorithm etc., but these algorithms need to simulate light in the scattering of interior of articles and absorbing state, and not only algorithm complex is large, and very consuming time.And some are simplified or the algorithm of approximate calculating subsurface BRDF, as Diffusion Approximation algorithm, Kubelka-Munk algorithm etc., its degree of accuracy is not high, the image played up and real industrial products similarity are inadequate, and cannot meet the characteristic that BRDF changes due to the change of angle of incidence of light thereupon.

Therefore, how to calculate the subsurface BRDF of multi-layer material object quickly and efficiently, and then calculate the BRDF of its correspondence, and can ensure that the BRDF that calculates can be the problem that solution is needed in one, computer graphical Rendering field badly close to the reflection characteristic of body surface as much as possible.

Summary of the invention

For this reason, needing the technical scheme of the real-time rendering that a kind of multi-layer material object is provided, adopting existing algorithm when calculating the subsurface BRDF of multi-layer material object in order to solve, the problem that algorithm complex is large, spended time is of a specified duration.

For achieving the above object, inventor provide a kind of real-time rendering method of multi-layer material object, comprise step:

According to the first optical property information of described multi-layer material object, calculating a BRDF, a described BRDF is the subsurface BRDF of the substrate material layers of described multi-layer material object;

According to the first optical property information of described multi-layer material object, calculating the 2nd BRDF, described 2nd BRDF is the subsurface BRDF after described multi-layer material object adds material layers in substrate material layers; The number of plies of the material layers of adding is one or more layers;

The second optical property information according to last material layers of adding calculates the 3rd BRDF;

The real-time rendering of described multi-layer material object is carried out based on described 2nd BRDF and the 3rd BRDF.

Further, the first optical property information of described multi-layer material object specifically comprises the first optical property information of the first optical property information of substrate material layers and the material layers of interpolation;

Described first optical property information comprises Scattering Phase Function and single scattering albedo, and described second optical property information comprises Fresnel reflection value and smoothness.

Further, the method calculating a BRDF specifically comprises: according to Scattering Phase Function and the single scattering albedo of described substrate material layers, adopts Ambartsumain integral equation iterative computation to go out the subsurface BRDF of this layer.

Further, the thickness of the material layers of described interpolation meets a preset threshold condition.

Further, the method calculating the 2nd BRDF specifically comprises: on the subsurface BRDF basis of last layer, use Invariant Imbedding method to calculate the subsurface BRDF after adding material layers.

Further, the method calculating the 3rd BRDF specifically comprises: use the second optical property information of last material layers of adding to calculate its Cook-Torrance BRDF.

Further, step " is carried out the real-time rendering of described multi-layer material object " and is specifically comprised based on described 2nd BRDF and the 3rd BRDF:

Linear superposition the 2nd BRDF and the 3rd BRDF, and generate rendering result according to stack result.

Inventor additionally provides a kind of real-time rendering device of multi-layer material object, comprise computing unit and real-time rendering unit, described computing unit comprises the first computing module, second computing module and the 3rd computing module, described first computing module is used for the first optical property information according to described multi-layer material object, calculate a BRDF, a described BRDF is the subsurface BRDF of the substrate material layers of described multi-layer material object; Described second computing module is used for the first optical property information according to described multi-layer material object, and calculating the 2nd BRDF, described 2nd BRDF is the subsurface BRDF after described multi-layer material object adds material layers in substrate material layers; The number of plies of the material layers of adding is one or more layers; Described 3rd computing module is used for calculating the 3rd BRDF according to the second optical property information of last material layers of adding; Described real-time rendering unit is used for the real-time rendering carrying out described multi-layer material object based on described 2nd BRDF and the 3rd BRDF.

Further, the first optical property information of described multi-layer material object specifically comprises the first optical property information of the first optical property information of substrate material layers and the material layers of interpolation;

Described first optical property information comprises Scattering Phase Function and single scattering albedo, and described second optical property information comprises Fresnel reflection value and smoothness.

Further, the method that the first computing module calculates a BRDF specifically comprises: according to Scattering Phase Function and the single scattering albedo of described substrate material layers, adopts Ambartsumain integral equation iterative computation to go out the subsurface BRDF of this layer.

Further, the thickness of the material layers of described interpolation meets a preset threshold condition.

Further, the method for the second computing module calculating the 2nd BRDF specifically comprises: on the subsurface BRDF basis of last layer, use Invariant Imbedding method to calculate the subsurface BRDF after adding material layers.

Further, the method for the 3rd computing module calculating the 3rd BRDF specifically comprises: use the second optical property information of last material layers of adding to calculate its Cook-Torrance BRDF.

Further, real-time rendering unit " carries out the real-time rendering of described multi-layer material object " and specifically comprises based on described 2nd BRDF and the 3rd BRDF:

Linear superposition the 2nd BRDF and the 3rd BRDF, and generate rendering result according to stack result.

Be different from prior art, first technique scheme according to the first optical property information of described multi-layer material object, calculates the subsurface BRDF of the substrate material layers of described multi-layer material object; Again according to the first optical property information of described multi-layer material object, calculate described multi-layer material object in substrate material layers, add material layers after subsurface BRDF, the number of plies of the material layers of interpolation is one or more layers; Then calculate the 3rd BRDF according to the second optical property information of last material layers of adding; The last real-time rendering carrying out described multi-layer material object based on described 2nd BRDF and the 3rd BRDF.The subsurface BRDF adding object after each material layers is calculated owing to adopting the mode of iteration, effectively avoid existing algorithm (as Ray Tracing Algorithm) needs simulation light to propagate at interior of articles process when calculating subsurface BRDF, thus greatly reduce the algorithm complex of the subsurface BRDF calculating multi-layer material object, shorten computing time, and then improve the efficiency of multi-layer material object being carried out to real-time rendering, thus in computer graphical Rendering field, there are wide market outlook.

Accompanying drawing explanation

Fig. 1 is the process flow diagram of the real-time rendering method of multi-layer material object described in an embodiment of the present invention;

Fig. 2 is the process flow diagram of the real-time rendering method of multi-layer material object described in another embodiment of the present invention;

Fig. 3 is the structural representation of the real-time rendering device of multi-layer material object described in an embodiment of the present invention.

Description of reference numerals:

1, computing unit; 11, the first computing module; 12, the second computing module; 13, the 3rd computing module;

2, real-time rendering unit.

Embodiment

By describe in detail technical scheme technology contents, structural attitude, realized object and effect, coordinate accompanying drawing to be explained in detail below in conjunction with specific embodiment.

Referring to Fig. 1, is the process flow diagram of the real-time rendering method of multi-layer material object described in an embodiment of the present invention; Described method can be applied to carries out real-time rendering to multi-layer material object, specifically comprises the steps:

First enter the first optical property information of step S1 according to described multi-layer material object, calculate a BRDF.Described multi-layer material object is object to be rendered, can be vehicle glass, furniture etc., multi-layer material in other words, these objects normally add material layers by a substrate material layers and spraying multilayer thereon and form, and layered coating is that the form successively superposed is sprayed on base material.Described first optical property information is the information characterizing object optical character, comprises light in the reflection of interior of articles, scattering, decay equal distribution situation.

Then can enter the first optical property information of step S2 according to described multi-layer material object, calculate the 2nd BRDF, described 2nd BRDF is the subsurface BRDF after described multi-layer material object adds material layers in substrate material layers, and the number of plies of the material layers of interpolation is one or more layers.After substrate material layers adds new material layers, the subsurface BRDF of described multi-layer material object will change, and thus need to recalculate subsurface BRDF.The number of plies of the material layers of adding can according to actual needs, and the number of plies is one or more layers, and the 2nd BRDF is the subsurface BRDF after described multi-layer material object adds one or more layers material layers in substrate material layers.

Then enter step S3 and calculate according to the second optical property information of last material layers of adding the surperficial BRDF that the 3rd BRDF, described 3rd BRDF are last material layers of adding.In order to the reflection characteristic of better reactant surface, make object carry out real-time rendering more close to the truth that light reflects at body surface, thus not only need the subsurface BRDF calculating object, and need the surperficial BRDF calculating object.And for multi-layer material object, the surperficial BRDF of the material layers of finally adding best embodies out the reflection characteristic of light at this body surface, thus the 3rd BRDF can be calculated according to the second optical property information of last material layers of adding, described second optical property information is the information characterizing object optical character, comprises the situation that reflection occurs at body surface light.Then can enter step S4 carries out described multi-layer material object real-time rendering based on described 2nd BRDF and the 3rd BRDF.2nd BRDF is the subsurface BRDF of last material layers of adding, 3rd BRDF is the surperficial BRDF of last material layers of adding, after carrying out the real-time rendering of described multi-layer material object based on described 2nd BRDF and the 3rd BRDF, " dummy model " of the multi-layer material object obtained can reflect the reflection characteristic of light at this body surface well.

First technique scheme according to the first optical property information of described multi-layer material object, calculates the subsurface BRDF of the substrate material layers of described multi-layer material object; Again according to the first optical property information of described multi-layer material object, calculate described multi-layer material object in substrate material layers, add material layers after subsurface BRDF, the number of plies of the material layers of interpolation is one or more layers; Then calculate the 3rd BRDF according to the second optical property information of last material layers of adding; The last real-time rendering carrying out described multi-layer material object based on described 2nd BRDF and the 3rd BRDF.The subsurface BRDF adding object after each material layers is calculated owing to adopting the mode of iteration, effectively avoid existing algorithm (as Ray Tracing Algorithm) needs simulation light to propagate at interior of articles process when calculating subsurface BRDF, thus greatly reduce the algorithm complex of the subsurface BRDF calculating multi-layer material object, shorten computing time, and then improve the efficiency of multi-layer material object being carried out to real-time rendering, thus in computer graphical Rendering field, there are wide market outlook.

In the present embodiment, first optical property information of described multi-layer material object specifically comprises the first optical property information of the first optical property information of substrate material layers and the material layers of interpolation, and described first optical property information comprises Scattering Phase Function and single scattering albedo.Because the material of different material layers is different, thus the first optical property information of their correspondences is not identical yet.In computer graphics, Scattering Phase Function (phase function) and single scattering albedo (single scattering albedo) is usually used to characterize the distribution situation of light at interior of articles.What Scattering Phase Function characterized is the distribution situation of light light when each scattering of interior of articles, and single scattering albedo is then the ratio of light scattering rate and light decay rate.Described second optical property information comprises Fresnel reflection value and smoothness, and Fresnel reflection value accounts for the number percent of incident ray for the light being characterized in body surface generation reflection, and smoothness is for characterizing the smoothness of body surface.

Multi-layer material object is made up of the material layers of substrate material layers and interpolation, by calculating the optical property information of the material layers of substrate material layers and interpolation, just the material layers of substrate material layers and interpolation can be converted to the manageable mathematical model of computing machine, the BRDF of being convenient to next carry out calculates and Rendering operations.In the present embodiment, mathematical model carries out computing in the space after carrying out Fourier transform, thus first needs Scattering Phase Function to carry out Fourier expansion.Particularly, first calculate the Fourier coefficients of Scattering Phase Function, can be calculated by following formula (1):

$p^m(\mathrm{\μ},{\mathrm{\μ}}^{\′})={(-1)}^m\underset{s=m}{\overset{s_{\max }}{\mathrm{\Σ}}}{\mathrm{\λ}}_s{P}_{m0}^s\left(\mathrm{\μ}\right)P_{m0}^s\left({\mathrm{\μ}}^{\′}\right)---\left(1\right)$

Wherein, m is m Fourier expansion item; μ is the cosine value of scattering direction zenith angle; p ^mthe Fourier coefficients that (μ, μ ') is Scattering Phase Function; for general spherical function (generalizedspherical function); λ _sfor Scattering Phase Function Legendre polynomial expansion coefficient, in this example, Scattering Phase Function adopts Henyey-Greenstein phase function, then λ _savailable following formula (2) represents:

λ _s＝(2s+1)g ^s(2)

Wherein, g is the asymmetry parameter (asymmetry parameter) of phase function.

As shown in Figure 2, in the present embodiment, the method calculating a BRDF specifically comprises: step S5, according to the Scattering Phase Function of described substrate material layers and single scattering albedo, adopts Ambartsumain integral equation iterative computation to go out the subsurface BRDF of this layer.Particularly, Ambartsumain integral equation is as shown in following formula (3):

$\begin{array}{c}({\mathrm{\μ}}_p+{\mathrm{\μ}}_q)R^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_q)=\frac{\mathrm{\α}}{4}{p}^m(-{\mathrm{\μ}}_p,{\mathrm{\μ}}_q)+\frac{\mathrm{\α}{\mathrm{\μ}}_q}{2}\underset{s=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{p}^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)R^m({\mathrm{\μ}}_s,{\mathrm{\μ}}_q)\\ +\frac{\mathrm{\α}{\mathrm{\μ}}_p}{2}\underset{s=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{p}^m({\mathrm{\μ}}_s,{\mathrm{\μ}}_q)R^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)\\ +\mathrm{\α}{\mathrm{\μ}}_p{\mathrm{\μ}}_q\underset{s=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{R}^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)\underset{s^{\′}=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ω}}_{s^{\′}}{p}^m({\mathrm{\μ}}_{s^{\′}},-{\mathrm{\μ}}_{s^{\′}})R^m({\mathrm{\μ}}_{s^{\′}},{\mathrm{\μ}}_q)\end{array}---\left(3\right)$

Wherein, α is single scattering albedo, is the ratio of light scattering rate corresponding to substrate material and light decay rate; R ^mfor the m time Fourier expansion term coefficient of BRDF; μ _ifor the cosine value of incident direction zenith angle; μ _ofor the cosine value of exit direction zenith angle.Formula (3) is converted into n × n numerical evaluation algebraic expression, shown in following formula (4):

$\begin{array}{c}({\mathrm{\μ}}_p+{\mathrm{\μ}}_q)R^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_q)=\frac{\mathrm{\α}}{4}{p}^m(-{\mathrm{\μ}}_p,{\mathrm{\μ}}_q)+\frac{\mathrm{\α}{\mathrm{\μ}}_q}{2}\underset{s=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{p}^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)R^m({\mathrm{\μ}}_s,{\mathrm{\μ}}_q)\\ +\frac{\mathrm{\α}{\mathrm{\μ}}_p}{2}\underset{s=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{p}^m({\mathrm{\μ}}_s,{\mathrm{\μ}}_q)R^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)\\ +\mathrm{\α}{\mathrm{\μ}}_p{\mathrm{\μ}}_q\underset{s=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{R}^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)\underset{s^{\′}=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ω}}_{s^{\′}}{p}^m({\mathrm{\μ}}_{s^{\′}},-{\mathrm{\μ}}_{s^{\′}})R^m({\mathrm{\μ}}_{s^{\′}},{\mathrm{\μ}}_q)\end{array}---\left(4\right)$

μ and ω is respectively the weight of quadrature node and its correspondence, shown in following formula (5) and (6):

${\mathrm{\μ}}_n=\cos (\frac{\mathrm{\π}}{4}{G}_n+\frac{\mathrm{\π}}{4})---\left(5\right)$

${\mathrm{\ω}}_n=\frac{\mathrm{\π}}{4}{W}_n\sin (\frac{\mathrm{\π}}{4}{G}_n+\frac{\mathrm{\π}}{4})---\left(6\right)$

Wherein, n maximal value is the number of quadrature node in interval [0,1], G _nfor Gaussian quadrature node; W _nfor the weight that Gaussian quadrature node is corresponding; R ^miteration initial value calculated by following formula (7):

$R^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_q)=\frac{\mathrm{\α}}{4({\mathrm{\μ}}_p+{\mathrm{\μ}}_q)}{p}^m(-{\mathrm{\μ}}_p,{\mathrm{\μ}}_q)---\left(7\right)$

Show through great many of experiments, after 10 iteration, the R of most of material ^m(the m time Fourier expansion term coefficient of BRDF) can reach convergence precision, also namely meets the requirement calculating BRDF.Thus now according to the R of substrate material layers ^mthe subsurface BRDF of substrate material layers can be calculated.

Accordingly, a BRDF calculates complete, then can calculate the 2nd BRDF according to a BRDF.

In the present embodiment, the optical thickness of the material layers of described interpolation meets a preset threshold condition.Predetermined threshold value according to the needs of algorithms of different, can adopt different threshold values.As shown in Figure 2, in the present embodiment, the method calculating the 2nd BRDF specifically comprises: step S6 uses Invariant Imbedding method to calculate the subsurface BRDF after adding material layers on the subsurface BRDF basis of last layer.Because Invariant Imbedding method can only calculate at most the scattering result of a light at every turn, thus require that the optical thickness of the material layers of adding needs enough little, such guarantee light mostly is once at the scattering imaging of this layer most, before calculating the 2nd BRDF, can by adjustment predetermined threshold value, make the optical thickness of the material layers of adding meet preset threshold condition, also namely meet light and mostly be once most at the scattering imaging of this layer.Invariant Imbedding method can on the basis of original BRDF, calculate the BRDF made new advances, this characteristic determines the subsurface BRDF that the method is suitable for calculating multi-layer material object very much, and the subsurface BRDF of substrate material layers has calculated according to above-mentioned formula (1) to (7), thus only need after material layers be added to substrate material layers at every turn, Invariant Imbedding method is all adopted to calculate the subsurface BRDF after adding material layers, calculate one by one, can calculate after material layers all adds, the subsurface BRDF of multi-layer material object, also be the 2nd BRDF.Particularly, the Fourier expansion term coefficient of the subsurface BRDF after adding material layers is first calculated, shown in the following formula of accounting equation (8):

$\begin{array}{c}{R}_n^m({\mathrm{\μ}}_0,{\mathrm{\μ}}_i)=(1-\frac{\mathrm{\Δ\τ}}{{\mathrm{\μ}}_0})R_{n-1}^m({\mathrm{\μ}}_0,{\mathrm{\μ}}_i)(1-\frac{\mathrm{\Δ\τ}}{{\mathrm{\μ}}_i})+\frac{a_n\mathrm{\Δ\τ}}{4{\mathrm{\μ}}_0{\mathrm{\μ}}_i}{p}_n^m(-{\mathrm{\μ}}_0,{\mathrm{\μ}}_i)\\ +\frac{a_n\mathrm{\Δ\τ}}{2{\mathrm{\μ}}_i}{\∫}_0^1{p}_n^m({\mathrm{\μ}}^{\′},{\mathrm{\μ}}_i)R_{n-1}^m({\mathrm{\μ}}_0,{\mathrm{\μ}}^{\′}){\mathrm{du}}^{\′}\\ +\frac{a_n\mathrm{\Δ\τ}}{{2\mathrm{\μ}}_0}{\∫}_0^1{p}_n^m({\mathrm{\μ}}_0,{\mathrm{\μ}}^{\′})R_{n-1}^m({\mathrm{\μ}}^{\′},{\mathrm{\μ}}_i){\mathrm{du}}^{\′}\\ +a_n\mathrm{\Δ\τ}{\∫}_0^1{R}_{n-1}^m({\mathrm{\μ}}_0,{\mathrm{\μ}}^{\′}){\mathrm{du}}^{\′}{\∫}_0^1{p}_n^m(-{\mathrm{\μ}}^{\′},{\mathrm{\μ}}^{\′\′})R_{n-1}^m({\mathrm{\μ}}^{\′\′},{\mathrm{\μ}}_i){\mathrm{du}}^{\′\′}\end{array}---\left(8\right)$

Wherein, n represents added n-th layer material, (n-1)th layer of (last layer) material that n-1 adds before representing interpolation n-th layer material, and α is single scattering albedo, is the ratio of light scattering rate corresponding to added material layers and light decay rate; R ^mfor the m time Fourier expansion term coefficient of BRDF; μ _ifor the cosine value of incident direction zenith angle; μ _ofor the cosine value of exit direction zenith angle, Δ τ represents the optical thickness of added material layers.Formula (8) is converted into algebraic manipulation equation, shown in following formula (9):

$\begin{array}{c}{R}_n^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_q)=(1-\frac{\mathrm{\Δ\τ}}{{\mathrm{\μ}}_p})R_{n-1}^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_q)(1-\frac{\mathrm{\Δ\τ}}{{\mathrm{\μ}}_q})+\frac{a_n\mathrm{\Δ\τ}}{4{\mathrm{\μ}}_p{\mathrm{\μ}}_q}{p}_n^m(-{\mathrm{\μ}}_p,{\mathrm{\μ}}_q)\\ +\frac{a_n\mathrm{\Δ\τ}}{2{\mathrm{\μ}}_q}\underset{s=1}{\overset{N}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{p}_n^m(-{\mathrm{\μ}}_s,{\mathrm{\μ}}_q)R_{n-1}^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)\\ +\frac{a_n\mathrm{\Δ\τ}}{2{\mathrm{\μ}}_p}\underset{s=1}{\overset{N}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{p}_n^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)R_{n-1}^m({\mathrm{\μ}}_s,{\mathrm{\μ}}_q)\\ +a_n\mathrm{\Δ\τ}\underset{s=1}{\overset{N}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{R}_{n-1}^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)\underset{s^{\′}=1}{\overset{N}{\mathrm{\Σ}}}{\mathrm{\ω}}_{s^{\′}}{p}_n^m(-{\mathrm{\μ}}_s,{\mathrm{\μ}}_{s^{\′}})R_{n-1}^m({\mathrm{\μ}}_{s^{\′}},{\mathrm{\μ}}_q)\end{array}---\left(9\right)$

Owing to the addition of new material layers, thus the subsurface BRDF of object also changes thereupon, thus needing the Fourier coefficients by calculating to reconstruct the subsurface BRDF of the object after adding material layers, following formula (10) can be adopted to calculate:

Wherein, for reflection direction position angle (azimuth angle); μ ₀for the cosine value of reflection direction zenith angle.

Accordingly, the 2nd BRDF calculates complete, and the 2nd BRDF calculated then can be adopted to carry out real-time rendering operation.

As shown in Figure 2, in the present embodiment, the method calculating the 3rd BRDF specifically comprises: step S7 uses the second optical property information of last material layers of adding to calculate its Cook-Torrance BRDF, second optical property information comprises Fresnel reflection value and smoothness, Fresnel reflection value accounts for the number percent of incident ray for the light being characterized in body surface generation reflection, and smoothness is for characterizing the smoothness of body surface.In order to the reflection characteristic of better reactant surface, make object carry out real-time rendering more close to the truth that light reflects at body surface, thus not only need the subsurface BRDF calculating object, and need the surperficial BRDF calculating object.What Cook-Torrance BRDF described is the high light partial reflectance of material layers, can according to the second optical property information of last material layers of adding, calculate its Cook-Torrance BRDF, the Cook-Torrance BRDF calculated is the surperficial BRDF of last material layers of adding, and is also the 3rd BRDF.

As shown in Figure 2, in the present embodiment, step " is carried out the real-time rendering of described multi-layer material object " and is specifically comprised based on described 2nd BRDF and the 3rd BRDF: step S8 linear superposition the 2nd BRDF and the 3rd BRDF, and generates rendering result according to stack result.Can be stored in texture mapping by the 2nd BRDF calculated, then import in renderer, renderer will carry out the real-time rendering of described multi-layer material object based on the 2nd BRDF and the 3rd BRDF.Particularly, following formula (11) is adopted to complete final real-time rendering:

L(ω ₀)＝R(ω ₀,ω _i)E(ω _i)(ω _i·n) (11)

Wherein, ω _ifor incident ray direction, ω ₀for reflection ray direction, n is the normal vector direction of body surface, and E is incident light radiancy, and L is the lighting color that correspondence direction obtains, and R is the BRDF of body surface.

First technique scheme according to the first optical property information of described multi-layer material object, calculates the subsurface BRDF of the substrate material layers of described multi-layer material object; Again according to the first optical property information of described multi-layer material object, calculate described multi-layer material object in substrate material layers, add material layers after subsurface BRDF, the number of plies of the material layers of interpolation is one or more layers; Then calculate the 3rd BRDF according to the second optical property information of last material layers of adding; The last real-time rendering carrying out described multi-layer material object based on described 2nd BRDF and the 3rd BRDF.The subsurface BRDF adding object after each material layers is calculated owing to adopting the mode of iteration, effectively avoid existing algorithm (as Ray Tracing Algorithm) needs simulation light to propagate at interior of articles process when calculating subsurface BRDF, thus greatly reduce the algorithm complex of the subsurface BRDF calculating multi-layer material object, shorten computing time, and then improve the efficiency of multi-layer material object being carried out to real-time rendering, thus in computer graphical Rendering field, there are wide market outlook.

And inventor additionally provides a kind of real-time rendering device of multi-layer material object, refers to Fig. 3, it is the structural representation of the real-time rendering device of an embodiment of the present invention multi-layer material object.Described device comprises computing unit 1 and real-time rendering unit 2, described first computing module 11 is for the first optical property information according to described multi-layer material object, calculate a BRDF, a described BRDF is the subsurface BRDF of the substrate material layers of described multi-layer material object; Described second computing module 12 is for the first optical property information according to described multi-layer material object, and calculating the 2nd BRDF, described 2nd BRDF is the subsurface BRDF after described multi-layer material object adds material layers in substrate material layers; The number of plies of the material layers of adding is one or more layers; Described 3rd computing module 13 is for calculating the 3rd BRDF according to the second optical property information of last material layers of adding; Described real-time rendering unit 2 is for carrying out the real-time rendering of described multi-layer material object based on described 2nd BRDF and the 3rd BRDF.

When using the real-time rendering device of multi-layer material object to carry out real-time rendering, first the first computing module 11 is according to the first optical property information of described multi-layer material object, calculates a BRDF.Described multi-layer material object is object to be rendered, can be vehicle glass, furniture etc., multi-layer material in other words, these objects normally add material layers by a substrate material layers and spraying multilayer thereon and form, and layered coating is that the form successively superposed is sprayed on base material.Described first optical property information is the information characterizing object optical character, comprises light in the reflection of interior of articles, scattering, decay equal distribution situation.

Then the second computing module 12 is according to the first optical property information of described multi-layer material object, calculate the 2nd BRDF, described 2nd BRDF is the subsurface BRDF after described multi-layer material object adds material layers in substrate material layers, and the number of plies of the material layers of interpolation is one or more layers.After substrate material layers adds new material layers, the subsurface BRDF of described multi-layer material object will change, and thus need to recalculate subsurface BRDF.The number of plies of the material layers of adding can according to actual needs, and the number of plies is one or more layers, and the 2nd BRDF is the subsurface BRDF after described multi-layer material object adds one or more layers material layers in substrate material layers.

Then the 3rd computing module 13 calculates according to the second optical property information of last material layers of adding the surperficial BRDF that the 3rd BRDF, described 3rd BRDF are last material layers of adding.In order to the reflection characteristic of better reactant surface, make object carry out real-time rendering more close to the truth that light reflects at body surface, thus not only need the subsurface BRDF calculating object, and need the surperficial BRDF calculating object.And for multi-layer material object, the surperficial BRDF of the material layers of finally adding best embodies out the reflection characteristic of light at this body surface, thus the 3rd BRDF can be calculated according to the second optical property information of last material layers of adding, described second optical property information is the information characterizing object optical character, comprises the situation that reflection occurs at body surface light.Then can enter step S4 carries out described multi-layer material object real-time rendering based on described 2nd BRDF and the 3rd BRDF.2nd BRDF is the subsurface BRDF of last material layers of adding, 3rd BRDF is the surperficial BRDF of last material layers of adding, after carrying out the real-time rendering of described multi-layer material object based on described 2nd BRDF and the 3rd BRDF, " dummy model " of the multi-layer material object obtained can reflect the reflection characteristic of light at this body surface well.

First technique scheme according to the first optical property information of described multi-layer material object, calculates the subsurface BRDF of the substrate material layers of described multi-layer material object; Again according to the first optical property information of described multi-layer material object, calculate described multi-layer material object in substrate material layers, add material layers after subsurface BRDF, the number of plies of the material layers of interpolation is one or more layers; Then calculate the 3rd BRDF according to the second optical property information of last material layers of adding; The last real-time rendering carrying out described multi-layer material object based on described 2nd BRDF and the 3rd BRDF.The subsurface BRDF adding object after each material layers is calculated owing to adopting the mode of iteration, effectively avoid existing algorithm (as Ray Tracing Algorithm) needs simulation light to propagate at interior of articles process when calculating subsurface BRDF, thus greatly reduce the algorithm complex of the subsurface BRDF calculating multi-layer material object, shorten computing time, and then improve the efficiency of multi-layer material object being carried out to real-time rendering, thus in computer graphical Rendering field, there are wide market outlook.

In the present embodiment, first optical property information of described multi-layer material object specifically comprises the first optical property information of the first optical property information of substrate material layers and the material layers of interpolation, and described first optical property information comprises Scattering Phase Function and single scattering albedo.Because the material of different material layers is different, thus the first optical property information of their correspondences is not identical yet.In computer graphics, Scattering Phase Function (phase function) and single scattering albedo (single scattering albedo) is usually used to characterize the distribution situation of light at interior of articles.What Scattering Phase Function characterized is the distribution situation of light light when each scattering of interior of articles, and single scattering albedo is then the ratio of light scattering rate and light decay rate.Described second optical property information comprises Fresnel reflection value and smoothness, and Fresnel reflection value accounts for the number percent of incident ray for the light being characterized in body surface generation reflection, and smoothness is for characterizing the smoothness of body surface.

Multi-layer material object is made up of the material layers of substrate material layers and interpolation, by calculating the optical property information of the material layers of substrate material layers and interpolation, just the material layers of substrate material layers and interpolation can be converted to the manageable mathematical model of computing machine, the BRDF of being convenient to next carry out calculates and Rendering operations.In the present embodiment, mathematical model carries out computing in the space after carrying out Fourier transform, thus first needs Scattering Phase Function to carry out Fourier expansion.Particularly, first the first computing module 11 calculates the Fourier coefficients of Scattering Phase Function, can be calculated by following formula (1):

$p^m(\mathrm{\μ},{\mathrm{\μ}}^{\′})={(-1)}^m\underset{s=m}{\overset{s_{\max }}{\mathrm{\Σ}}}{\mathrm{\λ}}_s{P}_{m0}^s\left(\mathrm{\μ}\right)P_{m0}^s\left({\mathrm{\μ}}^{\′}\right)---\left(1\right)$

Wherein, m is m Fourier expansion item; μ is the cosine value of scattering direction zenith angle; p ^mthe Fourier coefficients that (μ, μ ') is Scattering Phase Function; for general spherical function (generalizedspherical function); λ _sfor Scattering Phase Function Legendre polynomial expansion coefficient, in this example, Scattering Phase Function adopts Henyey-Greenstein phase function, then λ _savailable following formula (2) represents:

λ _s＝(2s+1)g ^s(2)

Wherein, g is the asymmetry parameter (asymmetry parameter) of phase function.

In the present embodiment, the method calculating a BRDF specifically comprises: according to Scattering Phase Function and the single scattering albedo of described substrate material layers, adopts Ambartsumain integral equation iterative computation to go out the subsurface BRDF of this layer.Particularly, Ambartsumain integral equation is as shown in following formula (3):

$\begin{array}{c}({\mathrm{\μ}}_p+{\mathrm{\μ}}_q)R^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_q)=\frac{\mathrm{\α}}{4}{p}^m(-{\mathrm{\μ}}_p,{\mathrm{\μ}}_q)+\frac{\mathrm{\α}{\mathrm{\μ}}_q}{2}\underset{s=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{p}^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)R^m({\mathrm{\μ}}_s,{\mathrm{\μ}}_q)\\ +\frac{\mathrm{\α}{\mathrm{\μ}}_p}{2}\underset{s=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{p}^m({\mathrm{\μ}}_s,{\mathrm{\μ}}_q)R^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)\\ +\mathrm{\α}{\mathrm{\μ}}_p{\mathrm{\μ}}_q\underset{s=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{R}^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)\underset{s^{\′}=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ω}}_{s^{\′}}{p}^m({\mathrm{\μ}}_{s^{\′}},-{\mathrm{\μ}}_{s^{\′}})R^m({\mathrm{\μ}}_{s^{\′}},{\mathrm{\μ}}_q)\end{array}---\left(3\right)$

Wherein, α is single scattering albedo, is the ratio of light scattering rate corresponding to substrate material and light decay rate; R ^mfor the m time Fourier expansion term coefficient of BRDF; μ _ifor the cosine value of incident direction zenith angle; μ _ofor the cosine value of exit direction zenith angle.Formula (3) is converted into n × n numerical evaluation algebraic expression, shown in following formula (4):

$\begin{array}{c}({\mathrm{\μ}}_p+{\mathrm{\μ}}_q)R^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_q)=\frac{\mathrm{\α}}{4}{p}^m(-{\mathrm{\μ}}_p,{\mathrm{\μ}}_q)+\frac{\mathrm{\α}{\mathrm{\μ}}_q}{2}\underset{s=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{p}^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)R^m({\mathrm{\μ}}_s,{\mathrm{\μ}}_q)\\ +\frac{\mathrm{\α}{\mathrm{\μ}}_p}{2}\underset{s=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{p}^m({\mathrm{\μ}}_s,{\mathrm{\μ}}_q)R^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)\\ +\mathrm{\α}{\mathrm{\μ}}_p{\mathrm{\μ}}_q\underset{s=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{R}^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)\underset{s^{\′}=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ω}}_{s^{\′}}{p}^m({\mathrm{\μ}}_{s^{\′}},-{\mathrm{\μ}}_{s^{\′}})R^m({\mathrm{\μ}}_{s^{\′}},{\mathrm{\μ}}_q)\end{array}---\left(4\right)$

μ and ω is respectively the weight of quadrature node and its correspondence, shown in following formula (5) and (6):

${\mathrm{\μ}}_n=\cos (\frac{\mathrm{\π}}{4}{G}_n+\frac{\mathrm{\π}}{4})---\left(5\right)$

${\mathrm{\ω}}_n=\frac{\mathrm{\π}}{4}{W}_n\sin (\frac{\mathrm{\π}}{4}{G}_n+\frac{\mathrm{\π}}{4})---\left(6\right)$

Wherein, n maximal value is the number of quadrature node in interval [0,1], G _nfor Gaussian quadrature node; W _nfor the weight that Gaussian quadrature node is corresponding; R ^miteration initial value calculated by following formula (7):

$R^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_q)=\frac{\mathrm{\α}}{4({\mathrm{\μ}}_p+{\mathrm{\μ}}_q)}{p}^m(-{\mathrm{\μ}}_p,{\mathrm{\μ}}_q)---\left(7\right)$

Show through great many of experiments, after 10 iteration, the R of most of material ^m(the m time Fourier expansion term coefficient of BRDF) can reach convergence precision, also namely meets the requirement calculating BRDF.Thus now according to the R of substrate material layers ^mthe subsurface BRDF of substrate material layers can be calculated.

Accordingly, a BRDF calculates complete by the first computing module 11, then can calculate the 2nd BRDF according to a BRDF.

In the present embodiment, the optical thickness of the material layers of described interpolation meets a preset threshold condition.Predetermined threshold value according to the needs of algorithms of different, can adopt different threshold values.In the present embodiment, the method calculating the 2nd BRDF specifically comprises: on the subsurface BRDF basis of last layer, use InvariantImbedding method to calculate the subsurface BRDF after adding material layers.Because Invariant Imbedding method can only calculate at most the scattering result of a light at every turn, thus require that the optical thickness of the material layers of adding needs enough little, such guarantee light mostly is once at the scattering imaging of this layer most, before calculating the 2nd BRDF, can by adjustment predetermined threshold value, make the optical thickness of the material layers of adding meet preset threshold condition, also namely meet light and mostly be once most at the scattering imaging of this layer.InvariantImbedding method can on the basis of original BRDF, calculate the BRDF made new advances, this characteristic determines the subsurface BRDF that the method is suitable for calculating multi-layer material object very much, and the subsurface BRDF of substrate material layers has calculated according to above-mentioned formula (1) to (7), thus only need after material layers be added to substrate material layers at every turn, Invariant Imbedding method is all adopted to calculate the subsurface BRDF after adding material layers, calculate one by one, can calculate after material layers all adds, the subsurface BRDF of multi-layer material object, also be the 2nd BRDF.Particularly, the Fourier expansion term coefficient of the subsurface BRDF after adding material layers is first calculated, shown in the following formula of accounting equation (8):

$\begin{array}{c}{R}_n^m({\mathrm{\μ}}_0,{\mathrm{\μ}}_i)=(1-\frac{\mathrm{\Δ\τ}}{{\mathrm{\μ}}_0})R_{n-1}^m({\mathrm{\μ}}_0,{\mathrm{\μ}}_i)(1-\frac{\mathrm{\Δ\τ}}{{\mathrm{\μ}}_i})+\frac{a_n\mathrm{\Δ\τ}}{4{\mathrm{\μ}}_0{\mathrm{\μ}}_i}{p}_n^m(-{\mathrm{\μ}}_0,{\mathrm{\μ}}_i)\\ +\frac{a_n\mathrm{\Δ\τ}}{2{\mathrm{\μ}}_i}{\∫}_0^1{p}_n^m({\mathrm{\μ}}^{\′},{\mathrm{\μ}}_i)R_{n-1}^m({\mathrm{\μ}}_0,{\mathrm{\μ}}^{\′}){\mathrm{du}}^{\′}\\ +\frac{a_n\mathrm{\Δ\τ}}{{2\mathrm{\μ}}_0}{\∫}_0^1{p}_n^m({\mathrm{\μ}}_0,{\mathrm{\μ}}^{\′})R_{n-1}^m({\mathrm{\μ}}^{\′},{\mathrm{\μ}}_i){\mathrm{du}}^{\′}\\ +a_n\mathrm{\Δ\τ}{\∫}_0^1{R}_{n-1}^m({\mathrm{\μ}}_0,{\mathrm{\μ}}^{\′}){\mathrm{du}}^{\′}{\∫}_0^1{p}_n^m(-{\mathrm{\μ}}^{\′},{\mathrm{\μ}}^{\′\′})R_{n-1}^m({\mathrm{\μ}}^{\′\′},{\mathrm{\μ}}_i){\mathrm{du}}^{\′\′}\end{array}---\left(8\right)$

Wherein, n represents added n-th layer material, (n-1)th layer of (last layer) material that n-1 adds before representing interpolation n-th layer material, and α is single scattering albedo, is the ratio of light scattering rate corresponding to added material layers and light decay rate; R ^mfor the m time Fourier expansion term coefficient of BRDF; μ _ifor the cosine value of incident direction zenith angle; μ _ofor the cosine value of exit direction zenith angle, Δ τ represents the optical thickness of added material layers.Formula (8) is converted into algebraic manipulation equation, shown in following formula (9):

$\begin{array}{c}{R}_n^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_q)=(1-\frac{\mathrm{\Δ\τ}}{{\mathrm{\μ}}_p})R_{n-1}^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_q)(1-\frac{\mathrm{\Δ\τ}}{{\mathrm{\μ}}_q})+\frac{a_n\mathrm{\Δ\τ}}{4{\mathrm{\μ}}_p{\mathrm{\μ}}_q}{p}_n^m(-{\mathrm{\μ}}_p,{\mathrm{\μ}}_q)\\ +\frac{a_n\mathrm{\Δ\τ}}{2{\mathrm{\μ}}_q}\underset{s=1}{\overset{N}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{p}_n^m(-{\mathrm{\μ}}_s,{\mathrm{\μ}}_q)R_{n-1}^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)\\ +\frac{a_n\mathrm{\Δ\τ}}{2{\mathrm{\μ}}_p}\underset{s=1}{\overset{N}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{p}_n^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)R_{n-1}^m({\mathrm{\μ}}_s,{\mathrm{\μ}}_q)\\ +a_n\mathrm{\Δ\τ}\underset{s=1}{\overset{N}{\mathrm{\Σ}}}{\mathrm{\ω}}_s{R}_{n-1}^m({\mathrm{\μ}}_p,{\mathrm{\μ}}_s)\underset{s^{\′}=1}{\overset{N}{\mathrm{\Σ}}}{\mathrm{\ω}}_{s^{\′}}{p}_n^m(-{\mathrm{\μ}}_s,{\mathrm{\μ}}_{s^{\′}})R_{n-1}^m({\mathrm{\μ}}_{s^{\′}},{\mathrm{\μ}}_q)\end{array}---\left(9\right)$

Owing to the addition of new material layers, thus the subsurface BRDF of object also changes thereupon, thus needing the Fourier coefficients by calculating to reconstruct the subsurface BRDF of the object after adding material layers, following formula (10) can be adopted to calculate:

Wherein, for reflection direction position angle (azimuth angle); μ ₀for the cosine value of reflection direction zenith angle.

Accordingly, the 2nd BRDF calculates complete by the second computing module 12, and the 2nd BRDF calculated then can be adopted to carry out real-time rendering operation.

In the present embodiment, the method that 3rd computing module 13 calculates the 3rd BRDF specifically comprises: use the second optical property information of last material layers of adding to calculate its Cook-Torrance BRDF, second optical property information comprises Fresnel reflection value and smoothness, Fresnel reflection value accounts for the number percent of incident ray for the light being characterized in body surface generation reflection, and smoothness is for characterizing the smoothness of body surface.In order to the reflection characteristic of better reactant surface, make object carry out real-time rendering more close to the truth that light reflects at body surface, thus not only need the subsurface BRDF calculating object, and need the surperficial BRDF calculating object.What Cook-Torrance BRDF described is the high light partial reflectance of material layers, can according to the second optical property information of last material layers of adding, calculate its Cook-Torrance BRDF, the Cook-Torrance BRDF calculated is the surperficial BRDF of last material layers of adding, and is also the 3rd BRDF.

In the present embodiment, step " is carried out the real-time rendering of described multi-layer material object " and is specifically comprised based on described 2nd BRDF and the 3rd BRDF: linear superposition the 2nd BRDF and the 3rd BRDF, and generates rendering result according to stack result.Can be stored in texture mapping by the 2nd BRDF calculated, then import in renderer, renderer will carry out the real-time rendering of described multi-layer material object based on the 2nd BRDF and the 3rd BRDF.Particularly, following formula (11) is adopted to complete final real-time rendering:

L(ω ₀)＝R(ω ₀,ω _i)E(ω _i)(ω _i·n) (11)

Wherein, ω _ifor incident ray direction, ω ₀for reflection ray direction, n is the normal vector direction of body surface, and E is incident light radiancy, and L is the lighting color that correspondence direction obtains, and R is the BRDF of body surface.

First technique scheme according to the first optical property information of described multi-layer material object, calculates the subsurface BRDF of the substrate material layers of described multi-layer material object; Again according to the first optical property information of described multi-layer material object, calculate described multi-layer material object in substrate material layers, add material layers after subsurface BRDF, the number of plies of the material layers of interpolation is one or more layers; Then calculate the 3rd BRDF according to the second optical property information of last material layers of adding; The last real-time rendering carrying out described multi-layer material object based on described 2nd BRDF and the 3rd BRDF.The subsurface BRDF adding object after each material layers is calculated owing to adopting the mode of iteration, effectively avoid existing algorithm (as Ray Tracing Algorithm) needs simulation light to propagate at interior of articles process when calculating subsurface BRDF, thus greatly reduce the algorithm complex of the subsurface BRDF calculating multi-layer material object, shorten computing time, and then improve the efficiency of multi-layer material object being carried out to real-time rendering, thus in computer graphical Rendering field, there are wide market outlook.

It should be noted that, in this article, the such as relational terms of first and second grades and so on is only used for an entity or operation to separate with another entity or operational zone, and not necessarily requires or imply the relation that there is any this reality between these entities or operation or sequentially.And, term " comprises ", " comprising " or its any other variant are intended to contain comprising of nonexcludability, thus make to comprise the process of a series of key element, method, article or terminal device and not only comprise those key elements, but also comprise other key elements clearly do not listed, or also comprise by the intrinsic key element of this process, method, article or terminal device.When not more restrictions, the key element limited by statement " comprising ... " or " comprising ... ", and be not precluded within process, method, article or the terminal device comprising described key element and also there is other key element.In addition, in this article, " be greater than ", " being less than ", " exceeding " etc. be interpreted as and do not comprise this number; " more than ", " below ", " within " etc. be interpreted as and comprise this number.

Those skilled in the art should understand, the various embodiments described above can be provided as method, device or computer program.These embodiments can adopt the form of complete hardware embodiment, completely software implementation or the embodiment in conjunction with software and hardware aspect.The hardware that all or part of step in the method that the various embodiments described above relate to can carry out instruction relevant by program has come, described program can be stored in the storage medium that computer equipment can read, for performing all or part of step described in the various embodiments described above method.Described computer equipment, includes but not limited to: personal computer, server, multi-purpose computer, special purpose computer, the network equipment, embedded device, programmable device, intelligent mobile terminal, intelligent home device, wearable intelligent equipment, vehicle intelligent equipment etc.; Described storage medium, includes but not limited to: the storage of RAM, ROM, magnetic disc, tape, CD, flash memory, USB flash disk, portable hard drive, storage card, memory stick, the webserver, network cloud storage etc.

The various embodiments described above describe with reference to the process flow diagram of method, equipment (system) and computer program according to embodiment and/or block scheme.Should understand can by the combination of the flow process in each flow process in computer program instructions realization flow figure and/or block scheme and/or square frame and process flow diagram and/or block scheme and/or square frame.These computer program instructions can being provided to the processor of computer equipment to produce a machine, making the instruction performed by the processor of computer equipment produce device for realizing the function of specifying in process flow diagram flow process or multiple flow process and/or block scheme square frame or multiple square frame.

These computer program instructions also can be stored in can in the computer equipment readable memory that works in a specific way of vectoring computer equipment, the instruction making to be stored in this computer equipment readable memory produces the manufacture comprising command device, and this command device realizes the function of specifying in process flow diagram flow process or multiple flow process and/or block scheme square frame or multiple square frame.

These computer program instructions also can be loaded on computer equipment, make to perform sequence of operations step on a computing device to produce computer implemented process, thus the instruction performed on a computing device is provided for the step realizing the function of specifying in process flow diagram flow process or multiple flow process and/or block scheme square frame or multiple square frame.

Although be described the various embodiments described above; but those skilled in the art are once obtain the basic creative concept of cicada; then can make other change and amendment to these embodiments; so the foregoing is only embodiments of the invention; not thereby scope of patent protection of the present invention is limited; every utilize instructions of the present invention and accompanying drawing content to do equivalent structure or equivalent flow process conversion; or be directly or indirectly used in other relevant technical fields, be all in like manner included within scope of patent protection of the present invention.

Claims (14)

1. a real-time rendering method for multi-layer material object, comprises step:

According to the first optical property information of described multi-layer material object, calculating a BRDF, a described BRDF is the subsurface BRDF of the substrate material layers of described multi-layer material object;

According to the first optical property information of described multi-layer material object, calculating the 2nd BRDF, described 2nd BRDF is the subsurface BRDF after described multi-layer material object adds material layers in substrate material layers; The number of plies of the material layers of adding is one or more layers;

The second optical property information according to last material layers of adding calculates the 3rd BRDF;

The real-time rendering of described multi-layer material object is carried out based on described 2nd BRDF and the 3rd BRDF.

2., in the real-time rendering method of multi-layer material object as claimed in claim 1, the first optical property information of described multi-layer material object specifically comprises the first optical property information of the first optical property information of substrate material layers and the material layers of interpolation;

Described first optical property information comprises Scattering Phase Function and single scattering albedo, and described second optical property information comprises Fresnel reflection value and smoothness.

3. in the real-time rendering method of multi-layer material object as claimed in claim 2, the method calculating a BRDF specifically comprises: according to Scattering Phase Function and the single scattering albedo of described substrate material layers, adopts Ambartsumain integral equation iterative computation to go out the subsurface BRDF of this layer.

4., in the real-time rendering method of multi-layer material object as claimed in claim 1 or 2, the thickness of the material layers of described interpolation meets a preset threshold condition.

5., in the real-time rendering method of multi-layer material object as claimed in claim 4, the method calculating the 2nd BRDF specifically comprises: on the subsurface BRDF basis of last layer, use Invariant Imbedding method to calculate the subsurface BRDF after adding material layers.

6., in the real-time rendering method of multi-layer material object as claimed in claim 1 or 2, the method calculating the 3rd BRDF specifically comprises: use the second optical property information of last material layers of adding to calculate its Cook-Torrance BRDF.

7., in the real-time rendering method of multi-layer material object as claimed in claim 1 or 2, step " is carried out the real-time rendering of described multi-layer material object " and is specifically comprised based on described 2nd BRDF and the 3rd BRDF:

Linear superposition the 2nd BRDF and the 3rd BRDF, and generate rendering result according to stack result.

8. the real-time rendering device of a multi-layer material object, comprise computing unit and real-time rendering unit, described computing unit comprises the first computing module, second computing module and the 3rd computing module, described first computing module is used for the first optical property information according to described multi-layer material object, calculate a BRDF, a described BRDF is the subsurface BRDF of the substrate material layers of described multi-layer material object; Described second computing module is used for the first optical property information according to described multi-layer material object, and calculating the 2nd BRDF, described 2nd BRDF is the subsurface BRDF after described multi-layer material object adds material layers in substrate material layers; The number of plies of the material layers of adding is one or more layers; Described 3rd computing module is used for calculating the 3rd BRDF according to the second optical property information of last material layers of adding; Described real-time rendering unit is used for the real-time rendering carrying out described multi-layer material object based on described 2nd BRDF and the 3rd BRDF.

9., in the real-time rendering device of multi-layer material object as claimed in claim 8, the first optical property information of described multi-layer material object specifically comprises the first optical property information of the first optical property information of substrate material layers and the material layers of interpolation;

Described first optical property information comprises Scattering Phase Function and single scattering albedo, and described second optical property information comprises Fresnel reflection value and smoothness.

10. in the real-time rendering device of multi-layer material object as claimed in claim 9, the method that first computing module calculates a BRDF specifically comprises: according to Scattering Phase Function and the single scattering albedo of described substrate material layers, adopts Ambartsumain integral equation iterative computation to go out the subsurface BRDF of this layer.

In the real-time rendering device of 11. multi-layer material objects as claimed in claim 8 or 9, the thickness of the material layers of described interpolation meets a preset threshold condition.

In the real-time rendering device of 12. multi-layer material objects as claimed in claim 11, the method that the second computing module calculates the 2nd BRDF specifically comprises: on the subsurface BRDF basis of last layer, use Invariant Imbedding method to calculate the subsurface BRDF after adding material layers.

In the real-time rendering device of 13. multi-layer material objects as claimed in claim 8 or 9, the method that the 3rd computing module calculates the 3rd BRDF specifically comprises: use the second optical property information of last material layers of adding to calculate its Cook-Torrance BRDF.

In the real-time rendering device of 14. multi-layer material objects as claimed in claim 8 or 9, real-time rendering unit " carries out the real-time rendering of described multi-layer material object " and specifically comprises based on described 2nd BRDF and the 3rd BRDF:

Linear superposition the 2nd BRDF and the 3rd BRDF, and generate rendering result according to stack result.