CN102289846A - Tree simulation method based on generalized parametric modeling - Google Patents

Abstract

The invention provides a tree simulation method based on generalized parametric modeling, comprising the steps of: step 1, inputting nongeometric parameters relevant to tree growth; step 2, selecting and reading corresponding geometrical data according to the nongeometric parameters, wherein the geometric data file is generated by the following mode: calibrating a tree seed function structure model on the basis of real-measurement data to obtain the tree seed function structure model, then utilizing the tree seed function structure model to generate a geometric data file of the tree seeds corresponding to different nongeometric parameter values; step 3, establishing a rudimentary model according to the geometric data file; step 4, inputting geometric parameters of a tree to adjust the rudimentary model so as to obtain a tree model; and step 5, carrying out fast and realistic drawing on the tree model. In the tree simulation method, the appearance form and the inner biological mechanism of the tree can be fully unified together, and a geometric model for fully reflecting the tree growth rule can be established.

Description

A kind of tree simulation method based on the broad sense parametric modeling

Technical field

The present invention relates to plant modeling and rendering technique, relate in particular to a kind of tree simulation method based on the broad sense parametric modeling.

Background technology

Floristics is various, comes in every shape, and complex structure, people are to the phytomorph structure, and finding out never of internal mechanism stops, and observes and be familiar with objective things with the mode of figure, is mankind's cognitive styles the most easily.Therefore, along with development of computer, the researchist has proposed the theory and the method for various plants visual Simulation, for the plant visual Simulation has been opened up wide road.

The plant visual Simulation mainly is the visual of tree modelling, comprises the drafting of trees modeling and trees, and this is visual two different phases, but both have common target---show trees truly.Below respectively trees modeling and trees drafting are introduced.

One, trees modeling

The trees modeling is to reflect the trees in the real world and can simulate the process of growth, development and the variation of trees by constructing a naive model.

Common several tree modeling methods mainly comprise: various improved L-system, fractal, the modeling based on image, particIe system, based on the modeling of parameter control.Yet in above modeling method, major part is only paid attention to the geometric shape, moulding of plant etc., seldom in conjunction with botany knowledge, therefore, can not simulate the advolution process of trees, is subjected to bigger restriction in the research of agriculture and forestry with in using.And this limitation of above method has promoted the development of structure functional mode, as Amap model (automaton model) and GreenLab model (functional architecture model) etc., these models had both been considered the morphosis of plant, considered the physiological ecological mechanism of plant again, can embody the true rule of plant growth preferably, the growth course of energy simulating plant, and can predict the upgrowth situation of plant.

The Amap model is the virtual plant model of a kind of L-of being different from system, combine the knowledge of the structural botany aspect of botanist's proposition, adopt finte-state machine to control the axle growth course of plant, thereby the topologies change in the simulate growth process, this technology are otherwise known as " axis of reference technology " or " stochastic process method ".

The GreenLab model is to improve on the Amap model based and expand, the GreenLab model has adopted two yardstick automats to come the form generating process of simulating plant, and the GreenLab model has formed the functional mode system that biomass distributes between more complete reflection plant organ.Be provided with the state of two levels in two yardstick automats---Macro Flags and little state, the growing element that the Macro Flags representative is different, little state is represented Ye Yuan, and Macro Flags is formed by little combinations of states.Two yardstick automaton models generate the topological structure of plant by the combination of this two states and the growth course of circulating analog plant.Automaton model in the Amap model, the expression-form of two yardstick automats and state parameter are often more succinct, also are more conducive to describe the plant growth characteristic relevant with growth cycle.The GreenLab model comes the biomass of each organ of simulating plant to distribute according to source-remittance theory of organ, and extrapolates the plant organ size over time by the biomass distribution on the basis of two yardstick automat form generation models.

The simulated technological process of GreenLab functional mode as shown in Figure 1, the GreenLab model comes the structure and the function feedback of simulating plant by a series of mathematical formulae iteration, compare other model, the GreenLab model has clear superiority aspect embodiment biomechanism and the model complexity, mainly contain following advantage: 1) represent growing element and the Ye Yuan of plant respectively, meet the characteristic that plant periodically grows with Macro Flags and little state.And the employing semi-Markov chain is described the relation between each state, more truly the growth of variation of the difference of simulating plant morphosis and plant.2) the GreenLab model has carried out a large amount of simplification to phytomorph structure and growth rhythm, difference according to each organ physiological age is classified each organ or branch, of a sort organ or branch adopt identical growth parameter(s), thereby simplified the plant growth parameter(s) greatly, and these growth parameter(s)s adopt the method for statistical fit to obtain, and can combine preferably with measured data.3) the GreenLab model has comparatively succinct form generation description form, and has set up the complete simulation biomass distribution and the functional mode of organ size variation, and the growth of simulating plant has comparatively truly been widely applied in the plant growth simulation at present.

But the GreenLab model still has many imperfection parts at present, does not also comprise the system model of considering various environmental factors, does not also further consider the physiology course in the plant, and this all remains improving and improving of researcher from now on.And because the geometric complexity of trees, the measurements of trees and GreenLab parameter fitting etc. are all had bigger difficulty, the research that at present GreenLab is applied to trees is difficulty relatively also.

Two, trees are drawn

The geometric model of trees is the visual bases of trees, realize that visual also needs of trees uses suitable algorithm that tree modelling is drawn out.It is exactly to utilize computer graphics techniques to handle the trees three-dimensional geometrical structure that trees are drawn, and generates the process of photorealism.

Along with tree modeling method enrich constantly and perfect, people more and more pay attention to the rendering technique of trees, at characteristics such as tree structure complexity, data volume are huge, people have proposed more rendering algorithm, mainly are classified as three classes according to the difference of drawing element: 1) based on how much method for drafting; 2) based on the method for drafting of image; 3) object plotting method.

1) method for drafting based on geometry is to adopt sweep trace method for drafting, ray tracing method, radiosity method, Ph0ton mapping technology to wait the geometric model of directly drawing trees.The trees geometric model is more true to nature, and is careful to model illumination, texture, shade and anti-aliasing processing, can generate effect very true to nature.But often dough sheet quantity is very big owing to trees geometric model true to nature, makes that the sense of reality drafting efficient of this method is very low, is difficult to satisfy in real time or the demand of interactive application.

2) based on the method for drafting of image.Drafting based on image utilizes texture image visually to simulate how much of trees, realizes that simply the dough sheet number is few, draws the efficient height.Rendering technique based on image is from the image angle, generate the image at different points of view place in the certain limit by operations such as interpolation, mixing, distortion, this method can greatly reduce the quantity of drawing geometric graphic element, improves render speed, has obtained using widely in interactive system.

Wherein, the fidelity of drafting depends on the fineness of texture image, and because image is the data that disperse, but when viewpoint was nearer, view data can not be segmented, and distortion phenomenon is apparent in view.And this method is just represented trees with one or several dough sheet, does not set up real trees geometric model, can not be applied to the simulation of the complex effects such as swing with the wind of dynamic illumination, tree branches.

3) object plotting method.The geometry complexity of object plotting method and trees is irrelevant, and can obtain the support of graphics accelerator hardware, in recent years, the high speed development with computer hardware updated along with algorithm, Volume Rendering Techniques has become the important tool of complex structure natural scene, in the real-time rendering field of forest scene a large amount of application has been arranged.But in volume drawing, whole trees, even a slice woods all are the integral body that can't cut apart, make and be difficult to the each several part zone of trees is controlled respectively and revised, also be difficult for expressing the complicated dynamic effect of trees, in dirigibility, seem not enough, and the volume drawing memory data output be big, computing time is longer, is subjected to certain restriction on using.

To sum up, existing plant visual Simulation technology also exists following deficiency:

1) for the trees modeling, the biology mechanism that prior art is failed the mode of appearance of trees is inner with it is fully united, and fails to set up the geometric model of abundant reflection arboreal growth rule.

2) draw for trees, prior art can not improve render speed when improving the drafting sense of reality, the quick rendering technique with good visual effect can be provided.

Summary of the invention

Technical matters to be solved by this invention provides a kind of tree simulation method based on the broad sense parametric modeling, can the biology mechanism that the mode of appearance of trees is inner with it fully unite, and can set up the fully geometric model of reflection arboreal growth rule.

In order to address the above problem, the invention provides a kind of tree simulation method based on the broad sense parametric modeling, comprising:

Step 1 is imported the non-geometric parameter relevant with arboreal growth;

Corresponding geometric data file is selected and read to step 2 according to described non-geometric parameter; Wherein the geometric data file generates in the following way: based on measured data one seeds functional architecture model is calibrated, obtain the functional architecture model of described seeds, utilize described functional architecture model to generate the geometric data file of the corresponding different non-geometric parameter values of described seeds then;

Step 3 is set up rudimentary model according to described geometric data file;

Step 4, the geometric parameter of input trees is adjusted described rudimentary model, obtains tree modelling;

Step 5 is carried out the quick sense of reality to described tree modelling and is drawn.

Preferably, in the above-mentioned tree simulation method, described non-geometric parameter comprises: seeds, age, season and/or water stress degree;

Described geometric parameter comprises: the diameter of a cross-section of a tree trunk 1.3 meters above the ground, base footpath, the height of tree, clear bole height, angle and/or flexibility.

Preferably, in the above-mentioned tree simulation method, described tree modelling is expressed geometry information and the topology information of trees based on binary tree.

Preferably, in the above-mentioned tree simulation method, described binary tree with the trees trunk as root node, side shoot on each trunk according to by the end to the top rank order, with first side shoot is left subtree, is right subtree with the sibling, and wherein said root node does not have right subtree.

Preferably, in the above-mentioned tree simulation method, before described step 5, also comprise:

Branch is sorted to the trees biomass with to the contribution degree of visual effect according to branch, reject the branch of ordering after threshold value then to simplify described tree modelling.

Preferably, in the above-mentioned tree simulation method, in described step 5, draw the translucent effect of blade by the method for class scattering; Draw the shade of trees by the echo method.

Preferably, in the above-mentioned tree simulation method, also comprise:

According to the arboreal growth conditional curve, between the tree modelling of each discrete state time point, carry out interpolation calculation, thereby generate the continuous animation of simulation trees growth and development process.

Preferably, in the above-mentioned tree simulation method, in described step 5, by adopting vertex cache, the disposable first step that submits the data to rendering pipeline, thereby minimizing data transmission realize drawing and quicken.

In order better to realize above-mentioned purpose, the present invention also provides a kind of tree simulation device based on the broad sense parametric modeling, comprising:

Load module is used for: import the non-geometric parameter relevant with arboreal growth;

Data acquisition module is used for: according to described non-geometric parameter, select and read corresponding geometric data file; Wherein the geometric data file generates in the following way: based on measured data one seeds functional architecture model is calibrated, obtain the functional architecture model of described seeds, utilize described functional architecture model to generate the geometric data file of the corresponding different non-geometric parameter values of described seeds then;

MBM is used for: set up rudimentary model according to described geometric data file;

Adjusting module is used for: the geometric parameter of input trees is adjusted described rudimentary model, obtains tree modelling;

Drafting module is used for: described tree modelling is carried out the quick sense of reality draw.

Preferably, in the above-mentioned tree simulation device, also comprise:

Simplify module, be used for: sort to the trees biomass with to the contribution degree of visual effect according to branch, reject the branch of ordering after threshold value then to simplify described tree modelling;

Effects module is used for: the translucent effect of drawing blade by the method for class scattering; Draw the shade of trees by the echo method;

Interpolating module is used for: according to the arboreal growth conditional curve, carry out interpolation calculation between the tree modelling of each discrete state time point, thereby generate the continuous animation of simulation trees growth and development process;

Accelerating module is used for: by adopting vertex cache, disposablely submit data the first step of rendering pipeline to, thereby reduce data transmission, realize drawing and quicken.

Compared with prior art, the embodiment of the invention has following effect:

1) embodiment of the invention proposes and has realized the method for broad sense parametrization trees modelings, seeds, age, season, breeding condition etc. are set up tree modelling as parameter, and can pass through the diameter of a cross-section of a tree trunk 1.3 meters above the ground, base footpath, the height of tree, clear bole height, parameter adjustment tree modelling such as angle and flexibility.This modeling method combines geometry appearance and its biological characteristics of trees, helps generating the geometric model of reflection arboreal growth rule, can the smooth and easy trees growth course of simulating naturally.

2) embodiment of the invention proposes the method that the trees topological structure is expressed and the trees geometric data is stored based on binary tree, binary tree structure defines according to similar occurring in nature tree construction, be important information organization form, be beneficial to trees modeling and growth simulation.The binary tree structure of embodiment of the invention definition can clearly be expressed the topological structure relation of trees, and can clearly express the inheritance of branches at different levels and the corresponding relation of each branch all ages and classes.The tree structure based on binary tree of embodiment of the invention definition is expressed and can be carried out the tree structure simplification to the trees biomass with to the contribution degree of visual effect according to branch.

3) embodiment of the invention is expressed according to the arboreal growth rule with based on the tree structure of binary tree, set up the growth equation that is applicable to the simulation arboreal growth, and the growth courses of trees changed the variation that is presented as branch length, radius, position, leaf position and quantity, to these variations interpolation calculation of growing, realized the level and smooth growth transition of trees.

4) embodiment of the invention has realized the drafting of trees shades based on Shadow map (echo) technology in addition, and adopts the method that is similar to scattering to realize the translucent effect of leaf, has improved the sense of reality that trees are drawn.Programmable features in conjunction with graphic hardware, the drafting of branch and blade and growth course interpolation are all carried out in Programmable GPU, and adopt the triangular mesh of the automatic assembling function generation trees of Geometry Shader, and improved render speed, quickened the demonstration of model.

Description of drawings

Fig. 1 is the simulated technological process figure of GreenLab functional mode;

Fig. 2 is the flow chart of steps of the method that provides of the embodiment of the invention;

Fig. 3 is the definition synoptic diagram of the geometric parameter that provides of the embodiment of the invention;

Fig. 4 is the synoptic diagram of the branch translation that provides of the embodiment of the invention;

Fig. 5 is that the branch that the embodiment of the invention provides branch angle variation synoptic diagram;

Fig. 6 is that the branch bending degree that the embodiment of the invention provides changes synoptic diagram;

Fig. 7 is the trees ternary tree structure representation synoptic diagram that the embodiment of the invention provides;

Fig. 8 is that the trees binary tree structure that the embodiment of the invention provides is expressed synoptic diagram;

Fig. 9 is the arboreal growth conditional curve that the embodiment of the invention provides;

The structural drawing of the tree simulation device that Figure 10 provides for the embodiment of the invention.

Embodiment

The invention will be further described below in conjunction with the drawings and specific embodiments.

Fig. 2 is the flow chart of steps of the method that provides of the embodiment of the invention, as shown in Figure 2, comprises based on the tree simulation method of broad sense parametric modeling:

Step 101 is imported the non-geometric parameter relevant with arboreal growth;

Corresponding geometric data file is selected and read to step 102 according to described non-geometric parameter; Wherein the geometric data file generates in the following way: based on measured data one seeds functional architecture model is calibrated, obtain the functional architecture model of described seeds, utilize described functional architecture model to generate the geometric data file of the corresponding different non-geometric parameter values of described seeds then;

Step 103 is set up rudimentary model according to described geometric data file;

Step 104, the geometric parameter of input trees is adjusted described rudimentary model, obtains tree modelling;

Step 105 is carried out the quick sense of reality to described tree modelling and is drawn.

Wherein, described non-geometric parameter comprises: seeds, age, season and/or water stress degree; Described geometric parameter comprises: the diameter of a cross-section of a tree trunk 1.3 meters above the ground, base footpath, the height of tree, clear bole height, angle and/or flexibility.

As seen, the embodiment of the invention is set up rudimentary model according to non-geometric parameter and the structure function model (GreenLab) relevant with arboreal growth, and can obtain tree modelling by the geometric parameter adjustment.Therefore, the embodiment of the invention combines geometry appearance and its biological characteristics (non-geometric parameter) of trees, helps generating the geometric model of reflection arboreal growth rule, can the smooth and easy trees growth course of simulating naturally.

Wherein, described tree modelling is expressed the trees topology information and is stored the trees geometry information based on binary tree.As root node, the side shoot on each trunk is left subtree according to by the rank order of the end to the top with first side shoot to described binary tree, is right subtree with the sibling with the trees trunk, and wherein said root node does not have right subtree.

Binary tree structure defines according to similar occurring in nature tree construction, is important information organization form, is beneficial to trees modeling and growth simulation.Therefore, the binary tree structure of embodiment of the invention definition can clearly be expressed the topological structure relation of trees, and can clearly express the inheritance of branches at different levels and the corresponding relation of each branch all ages and classes, can also carry out the tree structure simplification to the trees biomass with to the contribution degree of visual effect according to branch.

Before described step 105, also comprise: sort to the trees biomass with to the contribution degree of visual effect according to branch, reject the branch of ordering after threshold value then to simplify described tree modelling.

In the embodiment of the invention, draw and adopt following technology: in described step 105, draw the translucent effect of blade by the method for class scattering; Draw the shade of trees by the echo method; According to the arboreal growth conditional curve, between the tree modelling of each discrete state time point, carry out interpolation calculation, thereby generate the continuous animation of simulation trees growth and development process; By adopting vertex cache, the disposable first step that submits the data to rendering pipeline, thereby minimizing data transmission realize drawing and quicken.

Below, careful explanation is carried out in broad sense parametric modeling, binary tree, GPU drafting or the like.

(1) broad sense parametric modeling

The parametric modeling notion is used for industrial design the earliest, is meant that the planform of design object is relatively finalized the design, and can arrange size relationship with one group of parameter, by varying sized driving modification of design result.The parametric modeling of plant is to keep changing size, form and the angle of plant geometry under the constant substantially prerequisite of plant topological law, finishes modeling method to the structure of plant display model with limited geometric graphic element.

The major parameter of the broad sense parametric modeling that the embodiment of the invention proposes not only comprises the diameter of a cross-section of a tree trunk 1.3 meters above the ground, base footpath, the height of tree, clear bole height, geometric parameters such as branch angle and flexibility, also comprises non-geometric parameters such as age, season, moisture and seeds.Earlier call different geometric data files, set up corresponding tree modelling by non-geometric parameter, then can be according to the redjustment and modification tree modelling of geometric parameter.

The embodiment of the invention has been carried out experiments of measuring to willow 107 and capital two willow seeds of 2 poplars, and based on a large amount of measured datas the GreenLab model of these two seeds is calibrated, and has obtained its functional architecture model parameter.As previously mentioned, QINGYUAN software calculates according to the functional architecture model of these two seeds, exports its geometric data file.Like this, the system that the embodiment of the invention realized can handle willow 107 and capital two seeds of 2 poplars, and promptly " seeds " parameter value scope is this two-value.In addition, " age " and " season " is time scale, calls different geometric data files according to age and changes of seasons, sets up corresponding tree modelling; " season " parameter is used to control the variation of the trees outward appearance four seasons, and spring, summer, autumn, winters four value are arranged; " moisture condition " parameter is used to control the breeding condition of trees, value have slightly coerce, moderate is coerced and three kinds of normal water supplies.

It more than is the non-geometric parameter of tree modelling, and the definition of its geometric parameter as shown in Figure 3: the diameter of a cross-section of a tree trunk 1.3 meters above the ground is the trees trunk diameter of trees 1.3m eminence, the base footpath is the diameter of trees trunk bottom, the height of tree is the trunk total length, clear bole height be on the trunk first side shoot apart from the distance of trunk bottom, the branch angle is side shoot and trunk angle, and flexibility is the angle of each internode of side shoot.Mention in the embodiment of the invention branch angle and flexibility be the secondary side shoot branch angle and flexibility.

The embodiment of the invention is adjusted tree modelling by above-mentioned geometric parameter, changes the mode of appearance of trees.Thereby, make tree modelling more true to nature by revising the adjustment that each geometric parameter drives the trees mode of appearance.Geometric parameter changes adjustment to tree modelling only at trunk and secondary branch, and the evolution of other branches or blade is according to the conversion of his father's branch.

Embodiment of the invention trees trunk is made up of a plurality of internodes, the length of each internode is identical on the trunk, when revising the height of tree, in order to keep the constant of the whole relative position of trees, revise the length of internode according to the variation of the height of tree, thereby reach the effect of revising the height of tree.

Clear bole height is that first side shoot is apart from the distance of trunk base portion on the trunk, and the clear bole height that the embodiment of the invention is mentioned recently replaces with the percentage of the actual clear bole height and the height of tree.When revising tree branches when high, first branch carries out translation according to specified value, but may occur as several situations among Fig. 4 during translation: the first kind normal condition, first branch do not reach the position of second branch through translation.Second kind of situation, first branch are after translation, and second branch becomes clear bole height apart from the trunk distance from bottom, and this moment, the value of clear bole height changed.The third situation, first branch are separated with the branch of same type after translation, are referred in another bunch branch, have changed the one-piece construction of trees.

And in fact the tree branches spacing has certain rule, concerning willow, is concentrated in a certain zone with annotinous branch, is called bunch.Therefore when revising clear bole height, can consider all branches of first bunch of translation, rather than first branch.During the translation branch, sub-side shoot and all blades according to the binary tree search to the first bunch all and all of definition carry out whole translation according to the clear bole height of revising.

Tree branches is too many, a branch angle and differs, and for the ease of calculating, all secondary branches of the embodiment of the invention adopt same branch angle.When revising the branch angle, all secondary branches change thereupon.The branch angle is angle between first internode of side shoot and trunk, and on the plane that trunk and current side shoot are formed, current side shoot is rotating a branch angle around trunk, is the final position of current side shoot.As shown in Figure 5, when changing in the presence of the branch angle, when the relative position between each internode on the anterior branch constant, first internode position a of each branch ₀Can not change, therefore the position a of other internodes on anterior branch _j' all the position translation according to first internode obtains.

${a_j}^{\′}=a_0+\stackrel{\→}{a_0{a_j}^{\′}}$

Wherein

$\left\{\begin{array}{c}\left|\right|\stackrel{\→}{a_0{a_j}^{\′}}\left|\right|=\left|\right|\stackrel{\→}{a_0{a}_j}\left|\right|\\ \mathrm{dot}(\stackrel{\→}{a_{0}B},\stackrel{\→}{a_0{a_j}^{\′}})==\left|\right|\stackrel{\→}{a_{0}B}\left|\right|\×\left|\right|\stackrel{\→}{a_0{a_j}^{\′}}\left|\right|\×\cos ({\mathrm{\α}}^{\′}-\mathrm{\β})\end{array}\right.$

By above-mentioned, can obtain the translation vector of other internodes on anterior branch, all subtree branches and all blades on this internode in the binary tree traversal carries out it then

Translation.

$\stackrel{\→}{a_j{a_j}^{\′}}={a_j}^{\′}-a_j=a_0+\stackrel{\→}{a_0{a_j}^{\′}}-a_j$

The branch flexibility refers to the skew number of degrees of the relative branch inceptive direction of branch end direction, and branch is made up of a plurality of internodes, and each internode has the certain angle skew, finally formed branch bending, therefore, revise the branch bending degree and make the position of each internode all can change, as shown in Figure 6.When the modification flexibility was β, first internode position a0 and the a1 of each branch remained unchanged, to the position a of other internodes on anterior branch _j' obtain according to the position of preceding two internodes.

${a_j}^{\′}={a_{j-1}}^{\′}+\stackrel{\→}{{a_{j-1}}^{\′}{a_j}^{\′}}$

Wherein

$\left\{\begin{array}{c}\left|\right|\stackrel{\→}{{a_{j-1}}^{\′}{a_j}^{\′}}\left|\right|=\left|\right|\stackrel{\→}{a_{j-1}{a}_j}\left|\right|\\ \mathrm{dot}(\stackrel{\→}{{a_{j-2}}^{\′}{a_{j-1}}^{\′}},\stackrel{\→}{{a_{j-1}}^{\′}{a_j}^{\′}})==\left|\right|\stackrel{\→}{{a_{j-2}}^{\′}{a_{j-1}}^{\′}}\left|\right|\×\left|\right|\stackrel{\→}{{a_{j-1}}^{\′}{a_j}^{\′}}\left|\right|\×\cos \left(\mathrm{\β}\right)\end{array}\right.$

By above-mentioned formula, can obtain the translation vector of other any internodes on anterior branch, all subtree branches and all blades on this internode in the binary tree traversal carries out it then Translation.

$\stackrel{\→}{a_j{a_j}^{\′}}={a_j}^{\′}-a_j={a_{j-1}}^{\′}+\stackrel{\→}{{a_{j-1}}^{\′}{a_j}^{\′}}-a_j$

(2) express based on the tree structure of binary tree

One of core work of the broad sense parametric modeling system that the embodiment of the invention proposes is the data file in conjunction with the GreenLab model, the active data expression is proposed, the geometry information and the topology information of expressing the GreenLab tree modelling rationally and effectively.The embodiment of the invention is by the document format data of labor GreenLab model, extract useful trees data, set up the structure representations of trees based on binary tree, geometry information and the topology information of storage trees, and carried out the tree structure simplification based on binary tree.

1) expresses towards the tree structure of GreenLab

The tree structure complexity, branch is various, and the geometric data amount is big, makes the storage of the storage of trees geometric data and topology information have big difficulty, and it is most important therefore to adopt rational structure to express trees.The embodiment of the invention is based on the geometric data of GreenLab model and exports the tree structure simulation of carrying out, the existing multidigit researchist in front has carried out the plant structure analog operation based on the GreenLab functional architecture model, but major part still concentrates on the herbaceous plant, it is simple that herbaceous plant is compared tree structure, data volume is few, can directly adopt how much method for drafting to simulate, but tree structure complexity, the geometric data amount is big, must adopt effective and efficient manner that these data organizations are got up, express the topological structure of trees effectively and clearly express the trees geometry, thank to the principle of luxuriant gold for this reason, proposed ternary tree structure representation method according to trees axle construction.The ternary tree of its definition is a root node with the main shaft base portion, each node comprises three orderly and mutually disjoint ternary trees, wherein left subtree is represented this first side shoot from the top to bottom, middle subtree is its brother tree, right subtree is next axle, and wherein other nodes of each subtree are equally according to as above sequential expression.As shown in Figure 7, a left side is the tree structure with the digital simplification that each entity is numbered, and the right side is the ternary tree structure representation of this tree.

Ternary tree can clearly be expressed the topological structure of plant naturally, embodies the axle construction characteristics of plant, and each node of ternary tree comprised the geological information and the biological attribute information of entity, can clearly express the geometry information of trees.But tree structure complexity, its entity number is millions, the ternary tree complex structure of trees, its traversal and searching all compares difficulty, therefore the embodiment of the invention has proposed a kind of new expression, come the expression tree timber structure based on binary tree, and each node canned data is improved, more simple and clear than ternary tree.

2) express based on the tree structure of binary tree

Concerning the trees of a complexity, ternary tree structure data quantity stored is still bigger, originally can express with data as trunk, and ternary tree need be divided into a plurality of axles based on the expression of axle construction and expresses, data volume is bigger, to the trident traversal of tree with search more time-consumingly, greatly reduce drafting efficient.The embodiment of the invention is used the thinking of ternary tree, has proposed the tree structure expression based on binary tree, and the binary tree of definition is not a foundation with axle construction, and is base unit with the branch.The trees hierarchical structure is obvious, and has stronger self-similarity, and trees generally are divided into trunk and side shoot, and the similar again stalk tree of each side shoot still is divided into trunk and side shoot.The binary tree of embodiment of the invention definition is base unit with the branch, and side shoot is called the child of trunk, and the side shoot on the trunk is called the brother between mutually, and the left node of binary tree is stored its child's information, and right node is stored its fraternal information.

As shown in Figure 8, the trees geometry of left side for simplifying expressed for convenient, with numeral each side shoot is numbered.It is as follows to be used for the binary tree semantical definition that tree structure expresses: binary tree with the trees trunk as root node, side shoot on each trunk according to by the end to the top rank order, with first side shoot is left subtree, with its sibling is right subtree (root node does not have right subtree), to each side shoot equally according to top definition.Fig. 8 right side is the binary tree abstract expression of tree structure as defined above.

By as above definition,, can carry out following visit from the some nodes of binary tree:

(step 1) is its left node of visit earlier, the right subtree of its left node of depth-first traversal, up to right subtree is empty, then should left side node and the node sequence of visiting constitute all side shoots of this node representative trunk, and sequence order is the sequence of positions of side shoot on trunk.As from { 5}, earlier { 6}, depth-first visit right subtree is up to { 7}, then left node { 6} and node sequence { 7} formation branch { all side shoots of 5} of visit for its left node of visit.

(step 2) is if this node side shoot rank is n, if n=1 represents that then this node is a root node, by (the side shoot rank of all nodes of visiting in the step 1) is n+1.If n!=1, its father node is visited in depth-first, is n-1 up to the side shoot rank of node, by (the side shoot rank of all nodes of visiting in the step 1) is n, visits the side shoot node of these nodes, and it is all side shoots of n+1 that the node sequence that obtains has been represented the side shoot rank.As from { 5}, its level=2 visit its father node, up to { its rank of 1} is 1, then according to ({ 2}, { 5}, { 8}, { 9}, { 10}, { the side shoot rank of 11} is 2 to all nodes that the step 1) mode travels through.{ 3}, { 4}, { 6}, { it is all side shoots of 3 that 7} is the side shoot rank to visit these ranks then and be the side shoot node of all nodes of 2.

By above-mentioned traversal mode, but specify side shoot in the fast access tree structure, this shows the topological structure relation of the same energy of the binary tree clear and definite expression trees that the embodiment of the invention defines, and data have minimizing greatly than the ternary tree expression.When needs travel through or search for the trees data, reduced a lot of workloads, significantly reduced the time.

3) simplify based on the tree structure of binary tree

The tree structure complexity, along with the trees age growth, branch of trees and blade are more and more, the data volume of tree modelling can be increasing, and the drafting efficient of trees can reduce greatly, and the certain applications of tree modelling often visually the trees details to be required be not very high, if each details of trees is all exported drafting, can have a strong impact on drafting efficient, therefore be necessary it is simplified to reduce complexity, improve drafting efficient.

For geometric space information and the biomass spatial framework of leave tree, tree modelling is simplified and should be kept former crown form shape and biomass to distribute when reducing the model complexity as far as possible as far as possible.Consider the biomass assignment problem of trees, more low-level limb has been compiled the main biomass of trees, its space distribution can be represented the biomass space distribution of whole trees roughly, and more low-level limb constituted the crown skeleton of trees, is supporting other organ of trees.In addition, from the low-level to the high-level, the quantity of long shoot is fewer and feweri.Obviously, branch length is more little, and its contribution to visual effect is more little, and is more little to the contribution of biomass space distribution.Can according to branch the contribution of trees biomass and the contribution of visual effect be sorted to branch by considering that reducing tree branches simplifies tree structure, reject the smaller branch of contribution degree then to reach the effect of simplification.

By above analysis, the importance of branch depends primarily on the length of weight of branch (can be determined by the branch rank roughly) and branch.The definition branch the weight metric function as:

w＝w _level×w _length

W wherein _LengthBe the length weight of branch, count ratio by internode number and the maximum internode of tree branches and replace.w _LevelBe the weight of branch different stage, determine that count the internode number of each branch of one tree earlier, statistical is separated out other average internode of each side shoot level and counted N then according to statistical study _Level, look for a N _LevelIn maximal value N _MaxThen:

$w_{\mathrm{level}}=\frac{N_{\mathrm{level}}}{N_{\max }}$

To side shoot descending sort, obtain a side shoot numbered sequence A according to w, can be k threshold value of w appointment as required then, thereby A is divided into k discrete level of detail.

In actual application, can select suitable level of detail model to draw from the distance of viewpoint according to render target point, thereby when improving drafting efficient, keep the equivalence on vision and the biological significance to a certain extent.

4) growth course simulation

The trees data file of QINGYUAN software output is all ages and classes discrete state, can only embody the trees difference of each all ages and classes, can not embody the growth course of trees in every year and change.And the growth course of trees is simulated is the emphasis problem of tree simulation research, and the embodiment of the invention has been carried out interpolation calculation according to the arboreal growth conditional curve to each discrete state of trees, thereby has simulated the growth and development process of trees.

The growth course of trees mainly is presented as the new life of branch and comes off, and the new life of branch length and change in radius and blade and coming off is provided with seamlessly transitting of branch according to growth rhythm like this, can simulate growing of trees.And all ages and classes trees that binary tree is expressed are independently, do not have corresponding relation between identical branch all ages and classes state, carry out the corresponding relation that growth simulation need be set up each branch earlier.Tree structure expression based on binary tree can clearly embody the topology information of trees, helps the extraction and the arboreal growth simulation of branch corresponding relation.

5) growth interpolation

Higher and meet the animation process of plant growth rhythm in order to obtain temporal resolution, a series of models of QINGYUAN output can be regarded key frame, time scale between each key frame is 1 year, in the middle of each key frame, insert 365 frames, according to the growth rhythm in the branch 1 year key frame is carried out interpolation, generate 365 frames in the middle of this.Interpolation algorithm carries out according to following formula:

N＝k×S+(1-k)×E，k∈[0，1]

Wherein N is a current state, and S is an initial state, and E is a final state, and k is the interpolation ratio, and reality is and time correlation function.

The growth of trees is slowly-and vigorous-slowly-finally stop, so the curve of all age group increment change procedure is a growth equation that is the serpentine curve, curve is as shown in Figure 9.The characteristics of arboreal growth equation are:

(1) y (t)=0 when t=0.The starting condition that this condition should satisfy for the arboreal growth equation.

(2) there is an asymptote y (t)=A in y (t), and A is this arboreal growth maximum value.

(3) growth of trees is irreversible, makes that y (t) is the monotone nondecreasing function about age (t).

(4) y (t) is the continuous and smooth function curve about t.

The variation of biomass is presented as the variation of each branch of trees, comprises that mainly the quantity of internode increases the size variation of radius and the length variations of internode.The length variation of the quantity of internode, the size of radius and internode all meets the Logistics curve, in order to determine the parameter of Logistics curve, need know foliation time, growth characteristics and fallen leaves time that concrete trees are relevant.Carry out normalization to 1 year 365 days, willow germinates generally at late March, and t0 is made as 0.25 with the foliation phase, and the phase that stops growing, the phase t1 that will stop growing was made as 0.78, then becomes the leaf fall period generally in the middle ten days and the last ten days in September.Come approximate simulation logistics curvilinear equation with the sin function.

Earlier calculate the newborn internode of each branch in 1 year by S initial state and E final state and count Num, then the newborn internode number of branch is y (t) equation is as follows:

$y\left(t\right)=\left\{\begin{array}{c}0,t<t0\\ \mathrm{Num}\&times;\sin (\frac{\mathrm{\&pi;}}{2}\&times;\frac{t-t0}{t1-t0}),t0\&le;t\&le;t1\\ \mathrm{Num},t>t1\end{array}\right.$ Can draw each branch newborn internode number in each period by formula, thereby draw the leaf unit sum of each branch in each in period.The quantity of same blade also can change, and blade begins flavescence in late September, slowly comes off at the bottom of October, establishes the blade time t2=0.82 that begins to come off, and blade all fell in mid-December, t3=0.95, and this branch blade adds up to N _Leaf, then the newborn internode number of branch is y _Leaf(t) equation is as follows:

$y_{\mathrm{leaf}}=\left\{\begin{array}{c}0,t<t0\\ N_{\mathrm{leaf}}\&times;\sin (\frac{\mathrm{\&pi;}}{2}\&times;\frac{t-t0}{t1-t0}),t0\&le;t\&le;t1\\ N_{\mathrm{leaf}},t1<t<t2\\ N_{\mathrm{leaf}}\&times;\frac{t-t2}{t3-\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HDA0000089929370000043.png"\; state="\{\{state\}\}">t</figure-callout>}2},\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HDA0000089929370000043.png"\; state="\{\{state\}\}">t</figure-callout>}2\&le;t\&le;t3\\ 0,t\&GreaterEqual;t3\end{array}\right.$

Except the variation of branch length and blade quantity, the position of each internode and radius also can change in time on the branch, and the radius of establishing the internode primary state is r0, and internode final state radius is r1, and then the equation of internode radius r (t) is as follows:

$r\left(t\right)=\left\{\begin{array}{c}r0,t<t0\\ r0+(r1-r0)\&times;\sin (\frac{\mathrm{\&pi;}}{2}\&times;\frac{t-t0}{t1-t0}),t0\&le;t\&le;t1\\ r1,t>t1\end{array}\right.$

If the position of internode original state be p0 (x, y, z), the position of internode final state be p1 (x, y, z), then internode position p (z) equation of (t) is as follows for x, y:

$p\left(t\right)=\left\{\begin{array}{c}p0,t<t0\\ p0+(p1-p0)\&times;\sin (\frac{\mathrm{\&pi;}}{2}\&times;\frac{t-t0}{t1-t0}),t0\&le;t\&le;t1\\ p1,t>t1\end{array}\right.$

By above-mentioned equation, can from two growth age key frames, interpolation obtain 365 key frames, thereby realize the growth course interpolation of trees.

(3) trees sense of reality method for drafting

Trees are important composition factors of natural scene, and the existence of height sense of reality trees can promote the fidelity of a scene significantly, and the authenticity of trees visual effect has directly influenced the experience of immersing of virtual reality system.The trees visual details is various, have the uneven of crackle or knot bark surface, the translucent attribute that the old and new's leaf is different, the hatching effect of complexity between leaf and the trunk, the all non-easy thing of sense of reality simulation of these details, it is the problem of rich challenge in the computer graphics that trees true to nature represent always.The trees sense of reality of the embodiment of the invention is drawn the translucent effect and the trees hatching effect of blade is simulated, wherein the blade translucent effect adopts the method simulation of approximate scattering, and the shade drafting of trees adopts current echo (shadow map) method relatively more commonly used.

The drafting of blade

Draw the trees with height sense of reality, it is crucial drawing the leaf with height sense of reality.The complicacy on blade geometry, the crossover interaction of complicated effect of light, especially blade interior makes blade present semi-transparency property, thereby makes that sense of reality trees real-time rendering is very challenging efficiently.

The leaf of embodiment of the invention research is simulated with a quad patch that has shone upon blade transparent texture figure, rejects blade place in addition by the transparency test then.The size of quad patch is determined by var1 among the LigOrgan and var2, its initial position is all on XOY plane, with the true origin is the center, by the matrix matrix in the leaf structure current tetragonal position is rotated translation then, just blade can be plotted to corresponding correct position.

The drafting of shade

In the actual life, shade is ubiquitous, and shade is the crucial illumination visual signature of occurring in nature, and the drafting of shade not only can improve the sense of reality of scene, can also provide many important space geometry information for scene.The shade of trees can reflect spatial relation of trees and surrounding environment or trees self and mutual hiding relation etc., and the drafting of trees shade has bigger effect to the raising of the trees sense of reality.

The shade computing method that the embodiment of the invention adopts are echo (Shadow Map) methods more widely of using at present, its main thought is: when first pass is played up scene, the depth information of scene is kept on the texture maps, this texture maps is called depth map, then when drawing scene second time, information depth in the depth map is taken out, with comparing of current summit and light source apart from depth2, determine hiding relation, change the color of object then according to hiding relation, thus the simulation hatching effect.Because echo method principle is simple, be easy to realize and expansion, and the powerful processing power that can make full use of existing graphic hardware carries out real-time shadow efficiently and plays up, therefore become the shadow algorithm that is most widely used.

(4) drawing process based on GPU quickens

The arboreal growth of embodiment of the invention research be discrete model with each age as key frame, change according to how much between two frames then and the tree modelling of growth rhythm calculating current time, thereby generate continuous animation.The arboreal growth process is presented as the increase or the minimizing of each branch internode and blade, tree branches and leaf amount are many, data volume is big, if each repaints Shi Douxu constantly and calls the branch data again, large batch of like this data call, can increase the burden of CPU and GPU, draw efficient and can reduce greatly.Data volume be need reduce on the one hand so improve drafting efficient, date storage method or rendering algorithm needed to improve on the other hand.

The trees of embodiment of the invention research are drawn, data volume is mainly reflected on the branch, the trees of general life in 7 years, the number of blade is 7747, form by 7747 faces, the internode number is 14969, if each internode replaces with an octahedral cylinder, needs 14969 * 8 faces, simulate branch as if drawing quadrilateral between the glvertex that wants opengl, need call glvertex () function 14969 * 8 * 4 times, same if normal, texture coordinate are set, need call glnormal () and gltexcoord2f () equally 14969 * 8 * 4 times respectively, this situation is worthless, calls the opengl function in a large number and can reduce drafting efficient greatly, influences render speed.Embodiment of the invention employing VBO (vertex cache Vertex Buffer Objects) once submits the data to the first step of rendering pipeline, has reduced the efficient of data transmission.

The tree branches data preparation at n age is become n VBO,, select current VBO once to import rendering pipeline into,, branch position, length and radius etc. are carried out interpolation, generate continuous process then according to the time according to the age of current selection.

In addition, the embodiment of the invention also provides a kind of tree simulation device based on the broad sense parametric modeling, the structural drawing of the tree simulation device that Figure 10 provides for the embodiment of the invention, and as shown in figure 10, it comprises:

Load module 201 is used for: import the non-geometric parameter relevant with arboreal growth;

Data acquisition module 202 is used for: according to described non-geometric parameter, select and read corresponding geometric data file; Wherein the geometric data file generates in the following way: based on measured data one seeds functional architecture model is calibrated, obtain the functional architecture model of described seeds, utilize described functional architecture model to generate the geometric data file of the corresponding different non-geometric parameter values of described seeds then;

MBM 203 is used for: set up rudimentary model according to described geometric data file;

Adjusting module 204 is used for: the geometric parameter of input trees is adjusted described rudimentary model, obtains tree modelling;

Drafting module 205 is used for: described tree modelling is carried out the quick sense of reality draw.

Wherein, can also comprise:

Simplify module, be used for: sort to the trees biomass with to the contribution degree of visual effect according to branch, reject the branch of ordering after threshold value then to simplify described tree modelling;

Effects module is used for: the translucent effect of drawing blade by the method for class scattering; Draw the shade of trees by the echo method;

Interpolating module is used for: according to the arboreal growth conditional curve, carry out interpolation calculation between the tree modelling of each discrete state time point, thereby generate the continuous animation of simulation trees growth and development process;

Accelerating module is used for: by adopting vertex cache, the disposable first step that submits the data to the rendering pipeline of graphic process unit GPU, thereby minimizing data transmission realize drawing and quicken.

As from the foregoing, the embodiment of the invention has following advantage:

1) embodiment of the invention proposes and has realized the method for broad sense parametrization trees modelings, seeds, age, season, breeding condition etc. are set up tree modelling as parameter, and can pass through the diameter of a cross-section of a tree trunk 1.3 meters above the ground, base footpath, the height of tree, clear bole height, parameter adjustment tree modelling such as angle and flexibility.This modeling method combines geometry appearance and its biological characteristics of trees, helps generating the geometric model of reflection arboreal growth rule, can the smooth and easy trees growth course of simulating naturally.

2) embodiment of the invention proposes the method that the trees topological structure is expressed and the trees geometric data is stored based on binary tree, binary tree structure defines according to similar occurring in nature tree construction, be important information organization form, be beneficial to trees modeling and growth simulation.The binary tree structure of embodiment of the invention definition can clearly be expressed the topological structure relation of trees, and can clearly express the inheritance of branches at different levels and the corresponding relation of each branch all ages and classes.The tree structure based on binary tree of embodiment of the invention definition is expressed and can be carried out the tree structure simplification to the trees biomass with to the contribution degree of visual effect according to branch.

3) embodiment of the invention is expressed according to the arboreal growth rule with based on the tree structure of binary tree, set up the growth equation that is applicable to the simulation arboreal growth, and the growth courses of trees changed the variation that is presented as branch length, radius, position, leaf position and quantity, to these variations interpolation calculation of growing, realized the level and smooth growth transition of trees.

4) embodiment of the invention has realized the drafting of trees shades based on Shadow map technology in addition, and adopts approximate scattering method to realize the translucent effect of leaf, has improved the sense of reality that trees are drawn.Programmable features in conjunction with graphic hardware, the drafting of branch and blade and growth course interpolation are all carried out in Programmable GPU, and adopt the triangular mesh of the automatic assembling function generation trees of Geometry Shader, and improved render speed, quickened the demonstration of model.

The above only is a preferred implementation of the present invention; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (10)

1. the tree simulation method based on the broad sense parametric modeling is characterized in that, comprising:

Step 1 is imported the non-geometric parameter relevant with arboreal growth;

Corresponding geometric data file is selected and read to step 2 according to described non-geometric parameter; Wherein the geometric data file generates in the following way: based on measured data one seeds functional architecture model is calibrated, obtain the functional architecture model of described seeds, utilize described functional architecture model to generate the geometric data file of the corresponding different non-geometric parameter values of described seeds then;

Step 3 is set up rudimentary model according to described geometric data file;

Step 4, the geometric parameter of input trees is adjusted described rudimentary model, obtains tree modelling;

Step 5 is carried out the quick sense of reality to described tree modelling and is drawn.

2. tree simulation method according to claim 1 is characterized in that,

Described non-geometric parameter comprises: seeds, age, season and/or water stress degree;

Described geometric parameter comprises: the diameter of a cross-section of a tree trunk 1.3 meters above the ground, base footpath, the height of tree, clear bole height, angle and/or flexibility.

3. tree simulation method according to claim 1 and 2 is characterized in that, described tree modelling is expressed geometry information and the topology information of trees based on binary tree.

4. tree simulation method according to claim 3, it is characterized in that, described binary tree with the trees trunk as root node, side shoot on each trunk according to by the end to the top rank order, with first side shoot is left subtree, with the sibling is right subtree, and wherein said root node does not have right subtree.

5. tree simulation method according to claim 3 is characterized in that, before described step 5, also comprises:

Branch is sorted to the trees biomass with to the contribution degree of visual effect according to branch, reject the branch of ordering after threshold value then to simplify described tree modelling.

6. tree simulation method according to claim 3 is characterized in that, in described step 5, draws the translucent effect of blade by the method for class scattering; Draw the shade of trees by the echo method.

7. tree simulation method according to claim 6 is characterized in that, also comprises:

According to the arboreal growth conditional curve, between the tree modelling of each discrete state time point, carry out interpolation calculation, thereby generate the continuous animation of simulation trees growth and development process.

8. tree simulation method according to claim 7 is characterized in that, in described step 5, by adopting vertex cache, the disposable first step that submits the data to rendering pipeline, thereby minimizing data transmission realize drawing and quicken.

9. the tree simulation device based on the broad sense parametric modeling is characterized in that, comprising:

Load module is used for: import the non-geometric parameter relevant with arboreal growth;

Data acquisition module is used for: according to described non-geometric parameter, select and read corresponding geometric data file; Wherein the geometric data file generates in the following way: based on measured data one seeds functional architecture model is calibrated, obtain the functional architecture model of described seeds, utilize described functional architecture model to generate the geometric data file of the corresponding different non-geometric parameter values of described seeds then;

MBM is used for: set up rudimentary model according to described geometric data file;

Adjusting module is used for: the geometric parameter of input trees is adjusted described rudimentary model, obtains tree modelling;

Drafting module is used for: described tree modelling is carried out the quick sense of reality draw.

10. tree simulation device according to claim 9 is characterized in that, also comprises:

Simplify module, be used for: sort to the trees biomass with to the contribution degree of visual effect according to branch, reject the branch of ordering after threshold value then to simplify described tree modelling;

Effects module is used for: the translucent effect of drawing blade by the method for class scattering; Draw the shade of trees by the echo method;

Interpolating module is used for: according to the arboreal growth conditional curve, carry out interpolation calculation between the tree modelling of each discrete state time point, thereby generate the continuous animation of simulation trees growth and development process;

Accelerating module is used for: by adopting vertex cache, disposablely submit data the first step of rendering pipeline to, thereby reduce data transmission, realize drawing and quicken.

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