KR100951121B1 - Rendering method for indirect illumination effect - Google Patents

Abstract

PURPOSE: A rendering method for indirect illumination effect is provided to maximize physical accuracy compared with calculation time by minimizing an approximate calculation part in consideration of all paths of light corresponding to an indirect illumination part. CONSTITUTION: Visual information is generated through a visibility test about all pixels of a scene(S210). A general photon map and a non-diffuse photon map are respectively generated(S220). Simplified mesh information is generated(S230). An irradiance map of texture form is generated(S240). Through the irradiance map, the effect of a diffuse reflection irradiance is repetitively calculated about all pixels(S250). The effect of non-diffuse reflection irradiance is calculated(S270).

Description

Rendering method for indirect illumination effect

The present invention relates to a rendering technique that can generate a high-quality image that can be used in a movie or three-dimensional animation in a short time using the performance of the graphics processor, more specifically to reconstruct and render the rendering equation to suit the graphics processor A rendering method for indirect lighting processing that accelerates indirect lighting processing in an equation using a graphics processor.

Rendering technology refers to the final process of the graphics pipeline that gives reality while generating a three-dimensional description of a computer graphics scene as a two-dimensional image. As such, a rendering technology for generating a virtual 3D scene as a realistic image is a necessary technology for producing a real movie or 3D animation, and is recently applied to real-time applications such as games due to rapid development of hardware.

Recent advances in global illumination and shading technology have enabled the rendering of ultra-realistic images, but this requires a lot of computation time. In particular, by tracking the complex movement path of light in three-dimensional space based on physical theory, it is possible to automatically generate a more natural effect of global illumination. As such, the physics equation expressing the movement of light and the interaction with three-dimensional objects in order to generate the global lighting effect is called a rendering equation, which is the most basic theory for generating realistic images.

Traditional methods such as ray tracing, path tracing, radiosity, photon mapping, and final gathering have been studied to calculate these rendering equations. Several methods have been developed that extend or evolve these methods. However, these advanced methods still require a lot of computation time or have a problem of degrading quality when simplifying the rendering equation. Due to these problems, domestic or foreign small manufacturers who have not enough hardware (eg, render farms, etc.) for rendering, such as in large overseas productions, have to give up the use of such high quality rendering techniques.

Therefore, it is very important to shorten the calculation time while maintaining the quality of the image by making the most of the performance of hardware such as a PC currently available. The performance of personal computers, which are currently being deployed, is rapidly developing, and the performance of graphics processors (GPUs), which have been developed specifically for the real-time three-dimensional rendering pipeline, are developing more rapidly. There is also a significant change that allows users to execute programmed instructions on existing fixed pipelines. GPUs can execute instructions more restrictively than CPUs, but because they have hardware specific to a particular part, many methods have been found that can be computed faster using a graphics processor.

Until now, researches on realizing the global lighting effects such as ray tracing and simplified radiosity methods using a graphics processor in real time, or accelerating photon mapping techniques using a graphics processor, have been published. However, researches that accelerate the rendering techniques for high quality images that can be used in film or 3D animation using a graphics processor are difficult to find. As the existing prior art related to the global lighting effect, there is a "rendering device and method for real-time global lighting effect" of the Republic of Korea Patent Application No. 10-2004-0108828, but this is about a real-time rendering technique that can be used in games, etc. There is a difference in the purpose and method from the non-real time high quality image generation pursued by the present invention.

An object of the present invention for solving the above-described problems is to divide and calculate the rendering equation according to the type of radiance incident from the outside, which is required in non-real time applications such as movies or 3D animation, rather than real time applications such as games. It provides a rendering technique for indirect lighting processing that can provide a high quality image with low production time and low production cost.

Another object of the present invention is to provide a rendering technique capable of performing indirect lighting processing at high speed by utilizing the performance of a graphics processor (GPU) that has been specialized and developed for real-time three-dimensional rendering.

Another object of the present invention is to use a technique capable of generating a high quality image effectively in a multi- or streaming processor, which may have a particularly limited computing environment but has high performance in processing a large amount of data and referring to a memory, etc. It is to provide a rendering technique that can reduce the time and cost of producing a movie or 3D animation with superior performance on a general-purpose CPU by utilizing the performance of a graphics processor that has been specially developed for the purpose.

A feature of the present invention for achieving the above-described technical problem relates to a rendering method for the indirect lighting effect of the divided rendering equation, the rendering method,

)에 의한 효과를 계산하는 단계; (e) 상기 비확산 포톤 맵을 이용하여, 비확산반사광휘(

)에 의한 효과를 계산하는 단계;를 구비하고, 상기 확산반사광휘(

)는 포톤이 가시지점(x)에 입사하기 직전에 떠난 지점(y)에서 확산(diffuse) BRDF에 의해 반사된 광휘이며, 상기 비확산반사광휘(

)는 포톤이 가시지점(x)에 입사하기 직전에 떠난 지점(y)에서 비확산(non-diffuse) BRDF에 의해 반사된 광휘이다. (a) receiving information about a scene to be rendered; (b) generating visibility point information by performing a visibility check on the scene; (c) generating global photon maps and non-diffusion photon maps containing approximated luminance information using photon mapping techniques; (d) Diffuse reflectance luminance for all visible points using the global photon map;

Calculating the effect of; (e) Using the non-diffusion photon map, the non-diffuse reflectance luminance (

Computing the effect by; and, the diffuse reflection light (

) Is the luminance reflected by the diffuse BRDF at the point y left just before the photon enters the visible point (x), and the non-diffuse reflectance luminance (

Is the luminance reflected by the non-diffuse BRDF at point y where the photon left just before entering the visual point x.

In the step (d) of the rendering method having the above-mentioned characteristic, (d1) the luminance information input in the hemispherical direction with respect to the visible point by rendering the global photon map on each face of the semi-hexahedron for one visible point. Generating a semi-hexahedron comprising a; (d2) generating a direction map by sampling the hemisphere direction using the BRDF information on the visible point; (d3) loading the direction map for the visible point to sample the semi-hexahedral map for the visible point, and adding the sampled luminance information to calculate 1 × 1 pixels; (d4) repeating steps (d1) to (d4) for all visible points, and calculating 1 × 1 pixels for all visible points, respectively.

The step (e) of the rendering method having the above-mentioned characteristic may include (e1) a side having a length twice the maximum kernel radius R that is previously set around each photon by using the non-diffusion photon map. Forming a figure and first projecting the figure onto an image plane along a normal vector of a location where a corresponding photon is stored; (e2) measuring the number of photons primarily projected on each pixel constituting the image plane and storing the number of photons as pixel information of the corresponding pixel; (e3) adjusting kernel radii for each photon according to the number of photons stored as pixel information in each pixel; and (e4) accumulating luminance information in each pixel by applying the adjusted kernel radius in the process of reprojecting the figure generated in (e1) to the image plane around each photon and calculating the kernel. .

Another aspect of the invention relates to a rendering method for calculating an indirect lighting effect using a graphics processor (GPU), wherein the rendering method is

)에 의한 간접 조명 효과를 계산한다. (a) receiving information about a scene to be rendered; (b) generating visibility point information by performing a visibility check on the scene; (c) generating a global photon map containing approximated luminance information using photon mapping techniques; (d) rendering the global photon map on each face of the semi-hexahedron for one visible point to generate a semi-hexahedron including luminance information coming in the hemispherical direction with respect to the visible point; (e) sampling a hemisphere direction using the BRDF information for the visible point to generate a direction map; (f) loading the direction map for the visible point to sample the semi-hexahedral map for the visible point, and adding the sampled luminance information to calculate 1 × 1 pixels; (g) repeating steps (d) to (f) for all visible points and calculating 1 × 1 pixels for all visible points, respectively, wherein the photon is incident on the visible point x Diffuse reflectance luminance, which is the luminance reflected by the diffuse BRDF at the point y left just before

Calculate the indirect lighting effect by

Yet another aspect of the present invention relates to a rendering method for calculating an indirect lighting effect using a graphics processor (GPU), wherein the rendering method includes:

)에 의한 간접 조명 효과를 계산한다. (a) receiving information about a scene to be rendered; (b) generating visibility point information by performing a visibility check on the scene; (c) extracting photons reflected from the surface having the non-reflective BRDF using photon mapping technique, and generating a non-diffusion photon map using the extracted photons information; (d) using the non-diffusion photon map, form a figure having a side length of twice the preset maximum kernel radius R about each photon, and normalizing the figures at the location where the corresponding photon is stored. Primary projection along the vector to the image plane; (e) measuring the number of photons projected primarily on each pixel constituting the image plane and storing the number of photons as pixel information of the corresponding pixel; (f) adjusting kernel radii for each photon according to the number of photons stored as pixel information in each pixel; (g) accumulating luminance information in each pixel by applying the adjusted kernel radius in the process of reprojecting the figure generated in (d) onto an image plane around each photon and calculating a kernel; Non-diffuse reflectance luminance, which is a luminance reflected by a non-diffuse BRDF at a point y that leaves the photon just before entering the visible point (x);

Calculate the indirect lighting effect by

The rendering method according to the present invention is to generate a high quality image that can be used for a movie or 3D animation, and considers all the paths of light corresponding to the indirect lighting part in the rendering equation and minimizes the approximate calculation part in the calculation. It is a way. Therefore, it is a technique that can bring the effect of maximizing the physical accuracy compared to the calculation time. This reduces the parameters that need to be set for the lighting effect and automates the creation of realistic lighting effects through simplified parameters.

This improvement in automation can lead to a reduction in production time and cost. In the present invention, a large amount of high-performance hardware is provided by improving the performance by using a personal computer (PC) and a graphics processor. Even small manufacturers who are not doing so can be expected to increase efficiency using the physical-based renderer using this technique.

The present invention is also a rendering technique that effectively enables a rendering technique for generating a high quality image, which required a large amount of computation time in a CPU, through a graphics processor. Rendering method according to the present invention, in order to maximize the efficiency in a graphics processor having an input form and a calculation form different from the CPU, by dividing and reconstructing the rendering equation and converting the three-dimensional scene information and light information part of the rendering equation Among them, the indirect lighting calculation part that requires the most time is effectively calculated, and the photon mapping method and the final collection method, which are used recently, are applied to the graphics processor.

Accordingly, in the rendering method according to the present invention, the rendering equation is divided and calculated according to the type of radiance incident from the outside, thereby shortening the production time and cost of the 3D animation and effectively generating a high quality image.

Hereinafter, a rendering method for global illumination processing and a rendering apparatus to which the method is applied will be described in detail with reference to the accompanying drawings. In particular, the rendering method for the indirect lighting effect according to the present invention is performed by a graphics processor (GPU), by reducing and calculating the rendering equation according to the type of radiance incident from the outside, to reduce the time and cost of 3D animation production In addition, it is possible to effectively produce high quality images.

1 is a structural diagram illustrating hierarchically divided rendering equations in a rendering method for global illumination processing according to a preferred embodiment of the present invention. Equation 1 is the original rendering equation.

는 3차원 공간상의 한 지점에서 시점방향으로 들어오는 빛을 말하며,

는 해당 지점에서의 자체 발광에 의한 효과 부분이며,

는 외부로부터 해당 지점의 반구위 방향으로 입사하는 광휘에 의한 효과 부분으로서, 수학식 2와 같이 표현된다. here,

Refers to the light coming in the view direction from a point in three-dimensional space,

Is part of the effect of self-luminescence at that point,

Is an effect part due to light incident from the outside in the hemisphere direction of the corresponding point, and is expressed as in Equation 2 below.

이 분할된 렌더링 방정식이다. 이하, 도 1 및 수학식 3을 참조하여, 본 발명에 따라 렌더링 방정식의 분할 방법을 설명한다. Meanwhile, Equation 3 is according to the present invention.

This is a partitioned rendering equation. Hereinafter, a method of dividing a rendering equation according to the present invention will be described with reference to FIGS. 1 and 3.

을 제외하고,

에서 고려해야 하는 반구위 방향으로 입사하는 광휘를 크게 BRDF의 성질과 입사하는 빛의 성질에 따라 분해할 수 있다. 여기서, BRDF(Bidirectional Reflectance Distribution Function)는 물체의 표면에 대한 반사 속성 정보이다. As shown in Equation 3, the rendering equation is the part of the effect

Except

In the hemispherical direction, which should be considered in, the luminance can be largely decomposed according to the properties of the BRDF and the incident light. Here, BRDF (Bidirectional Reflectance Distribution Function) is reflection property information on the surface of the object.

를 분할한다. 도 1을 참조하면, 먼저 물체의 BRDF의 성질에 따라 반구위 방향을 정반사 방향과 비정반사 방향으로 분할하고, 이중 정반사(Specular) 방향을 통해 입사한 간접 광휘를

라 표기한다. 나머지 비정반사(nonspecular) 방향을 통해 입사하는 간접 광휘를 광원으로부터 직접 들어오는 직접광(direct light)의 방향과 공간상의 다른 물체와 1회 이상 상호작용 후 들어오는 간접광(indirect light)의 방향으로 분할하고, 이중 직접광의 방향에 대한 광휘를

로 표기한다. 다시, 나머지 간접광에 대한 방향 집합을 (1) 정반사 방향으로만 반사 또는 굴절된 간접광, (2) 정반사와 비정반사 방향 모두를 포함하고 있는 간접광 중 최종 반사 또는 굴절 방향이 난반사 방향인 간접광, 그리고 (3) 정반사와 비정반사 방향 모두를 포함하고 있는 간접광 중 최종 반사 또는 굴절 방향이 비난반사 방향인 간접광으로 분할하고, 이들 방향 집합에 의해 계산되는 광휘를 각각

,

,

으로 표기한다. 이렇게 렌더링 방정식에서 복잡한 계산을 요하는 반구위 방향에 대한 적분을 누락되는 방향없이 분할함으로서 기존에 이미 제안된 방법 및 본 발명에서 제안하는 방법을 각 부분에 적용하여 효과적으로 전체 방정식을 계산할 수 있게 된다. 특히

,

,

의 세가지 광휘 요소들은 기존의 여러 효율적인 방법들을 사용하여 계산이 가능하다. 본 발명에서는 정반사와 비정 반사를 가지는 간접광에 의한 광휘를 가시지점(

)에 입사하기 직전에 떠난 지점에서 확산(diffuse) BRDF에 의해 반사된 광휘(

)와 가시지점(

)에 입사하기 직전에 떠난 지점에서 비확산(non-diffuse) BRDF에 의해 반사된 광휘(

)로 분할함으로서, 전역 조명 효과 처리에 있어서 실제로 가장 계산이 어려운 비정반사(

와

를 제외한) 간접 조명 부분을 효과적으로 계산할 수 있도록 한다.

부분은 최종 모음 기법을 그래픽스 프로세서를 사용하여 가속화 함으로서 노이즈가 제거된 고품질의 간접 조명을 계산하고,

는 최종 모음 기법에 적합하지 않는 성질의 광휘 정보를 표현하고 있으므로 적응적인 photon splat 기법을 그래픽스 프로세서에 빠르게 계산한다.In the present invention, firstly, the integral part of the original rendering equation includes all the elements to be calculated, and secondly, to satisfy the condition that each part can be effectively calculated.

Split Referring to FIG. 1, first, the hemispherical direction is divided into the specular reflection direction and the non-reflection direction according to the property of BRDF of the object, and the indirect radiance incident through the double specular reflection direction is defined.

It is written as Indirect light incident through the remaining nonspecular directions is divided into the direction of direct light coming directly from the light source and the direction of indirect light coming after one or more interactions with other objects in space. For the direction of the double direct light

It is written as. Again, the indirect light in which the set of directions for the remaining indirect light are reflected or refracted only in the specular reflection direction, and (2) the indirect light in which the final reflection or refraction direction is the diffuse reflection direction among indirect light including both the specular and non-reflective directions (3) The indirect light including both the specular and non-reflective directions is divided into indirect light in which the final reflection or refraction direction is the non-reflective direction, and the luminance calculated by the set of these directions is respectively divided.

,

,

Mark as. In this way, by dividing the integral for the hemisphere direction requiring a complicated calculation in the rendering equation without a missing direction, it is possible to effectively calculate the entire equation by applying the previously proposed method and the method proposed in the present invention to each part. Especially

,

,

The three brightness components of can be calculated using many existing efficient methods. In the present invention, the brightness of the indirect light having a specular reflection and non-reflective point of view (

The luminance reflected by the diffuse BRDF at the point just before entering

) And the point of view (

Luminance reflected by a non-diffuse BRDF at the point just before entering

By dividing by), it is actually the most difficult to calculate non-reflective (

Wow

Indirect lighting can be calculated effectively.

Part accelerates the final vowel technique using a graphics processor to calculate high-quality indirect lighting without noise,

Because we represent luminance information that is not suitable for the final vowel technique, we can quickly compute the adaptive photon splat technique on the graphics processor.

,

,

,

의 요소는 기존의 방법을 이용하여 계산하며, 간접 광원에 의한 조명 처리를 위한 요소인

,

에 대한 계산 방법만을 제시한다. In calculating the rendering equation divided to have the above-described configuration, in the present invention,

,

,

,

The element of is calculated by using the existing method, which is an element for processing light by indirect light source.

,

Only the calculation method for.

Hereinafter, a rendering method for indirect lighting effects according to a preferred embodiment of the present invention will be described in detail with reference to FIGS. 2 and 3. 2 is a flowchart sequentially illustrating a rendering method for an indirect lighting effect according to the present invention, and FIG. 3 is a conceptual diagram for explaining an illumination process by an indirect light source incident on a nonspecular surface according to the present invention. It is shown as.

Referring to FIG. 2, first, scene information to be rendered is received (step 200). Here, the scene information includes all information representing a scene to be rendered in a virtual three-dimensional space, such as three-dimensional object, light source, and camera information having surface material information.

Next, a visibility test is performed on all pixels constituting the scene to detect visible points, and information about the detected visible points is generated (step 210). The visibility test can be effectively calculated through various techniques included in an image space method or an object space method. Since the visibility test method is variously performed in the art, a detailed description of the visibility test that is not related to the gist of the present invention will be omitted.

Next, a global photon map and a non-diffusion photon map including approximated multi-reflected luminance information are generated through the photon mapping technique (step 220). In order to use the approximated luminance information, the shading information by the direct light source may be calculated and used. The non-diffusion photon map is a photon map generated by extracting photons reflected from a surface having non-reflective BRDF.

Next, in order to improve the computational performance of the graphics processor while maintaining the image quality, simplified mesh information is generated (step 230). The generated mesh information is saved as a file and used in the later process.

Next, the global photon map is converted into an intensity map of a texture form that can be effectively expressed in a graphics processor (step 240). The process of converting to the luminance map can also be calculated very efficiently using the GPU.

)에 의한 효과를 모든 픽셀에 대하여 반복적으로 계산한다(단계 250). 상기 확산 반사 광휘(

)는 간접광에 의한 광휘 중 비정반사 표면을 갖는 가시시점(

)에 입사하기 직전에 떠난 지점으로부터 확산(diffuse) BRDF에 의해 반사된 광휘를 말하는 것으로서, 도 3에 도시된 가시지점(

)에 입사하기 직전에 떠난 지점이 확산 표면(diffuse surface)를 갖는 경우에 해당된다. 단계 250에 대하여 구체적인 설명은 후술한다. Next, the diffuse reflection luminance using the luminance map (

Is computed repeatedly for every pixel (step 250). The diffuse reflection luminance (

) Is the field of view () with the non-reflective surface of the luminance caused by indirect light.

Refers to the brightness reflected by the diffuse BRDF from the point left just before entering the

This corresponds to the case where a point left just before entering into a has a diffuse surface. Details of operation 250 will be described later.

)에 의한 효과를 계산한다(단계 270). 상기 비확산 반사 광휘(

)는 정반사와 비정반사를 가지는 간접광에 의한 광휘 중 가시시점(

)에 입사하기 직전에 떠난 지점에서 비확산(non-diffuse) BRDF에 의해 반사된 광휘를 말하는 것으로서, 도 3에 도시된 가시지점(

)에 입사하기 직전에 떠난 지점이 비확산 표면(nondiffuse surface)를 갖는 경우에 해당된다. 단계 270에 대하여 구체적인 설명은 후술한다. Next, a two-step photon projection process allows

Is calculated (step 270). The non-diffuse reflective brightness (

) Is the visible point of luminance of indirect light with specular and non-reflective light.

) Refers to the brightness reflected by the non-diffuse BRDF at the point immediately before entering the

This is the case where the point left just before entering a) has a nondiffuse surface. Details of operation 270 will be described later.

Through the above-described process, it is possible to calculate the effect of indirect lighting according to the present invention.

)에 의한 효과를 계산하는 과정(도 2의 단계 250에 해당됨)을 구체적 으로 설명한다. 도 4는 본 발명에 따른 렌더링 방법 중 확산 반사 광휘(

)에 의한 효과를 계산하는 과정을 순차적으로 도시한 흐름도이며, 도 5는 확산 반사 광휘의 계산 과정을 설명하기 위하여 도시한 도면이다. 도 5에 있어서, 현재 시점으로부터 보이는 3차원 물체위 가시지점(

)에 대하여,

는 법선 방향,

는 시점 방향,

는 반구위 방향에 대해 2차원 매개변수(i,j)로 표현된 샘플 방향,

는

를 샘플링할 때 사용된 2차원 매개변수 공간의 해상도로서, 총

개의 샘플링을 수행한 것을 각각 의미한다.Hereinafter, the diffuse reflection luminance of the indirect light illumination effect according to the present invention with reference to FIGS.

) Will be described in detail the process (corresponding to step 250 of FIG. 2). 4 is a diffuse reflection luminance of a rendering method according to the present invention;

FIG. 5 is a flowchart sequentially illustrating a process of calculating an effect of FIG. 5, and FIG. 5 is a diagram illustrating a process of calculating diffuse reflection luminance. In FIG. 5, the visible point on the three-dimensional object seen from the current viewpoint (

)about,

The normal direction,

Is the view direction,

Is the sample direction expressed as a two-dimensional parameter (i, j) for the hemisphere direction,

Is

Resolution of the two-dimensional parameter space used when sampling

Means that each of two samplings is performed.

)에서 반구 방향으로 들어오는 광휘 정보를 포함하는 반육면체 를 생성한다(단계 252). Referring to FIG. 4, first, a luminance map and simplified mesh information are rendered on five surfaces of a semi-hexahedron to generate a visible point (

In step 252, a semi-hexahedron including luminance information coming in the hemisphere direction is generated.

)에 대한 BRDF 정보의 특성을 반영하는 반구위 방향 샘플 집합들로 구성되는 방향 맵(direction map)을 기준 지역 좌표계(local coordinate)안에서 생성하고 이를 텍스쳐 형태로 저장한다(단계 254). Next, the point of view (

A direction map, which consists of sets of hemisphere orientation samples reflecting the characteristics of BRDF information, is generated in a reference local coordinate system and stored in a texture form (step 254).

Next, the semi-hexahedron is sampled by converting each sample direction of the stored direction map into an individual local coordinate system at a point where shading calculation is performed in the sampled reference local coordinate system. Step 256 provides information about the sample direction of the direction map. More efficient calculation by loading into the texture of the graphics processor, loading the luminance map stored in the semi-hexahedron into a cube map, and then performing hardware accelerated sampling on the cube map using a pixel shader. Will be performed.

Next, the luminance information obtained by sampling the hexahedral map is summed using a mipmap operation provided in hardware by the graphics processor to obtain final indirect illumination in the form of 1 × 1 pixel (step 258).

)을 수행하는 것으로서, 모든 가시 지점에 대해 이 단계들을 반복해서 수행하거나 캐싱 방법등을 사용해 효과적으로 모든 픽셀에 대한 간접 조명 정보를 생성하게 된다.By repeating steps 252 to 256 described above for all visible points, calculating 1 × 1 pixels for all visible points (step 259) and reading them into main memory, thereby calculating the effect by diffused reflection light. To complete. As such, by only bringing 1 × 1 result pixels by the mipmap operation into the main memory, overhead due to data movement between memories can be minimized. That is, in step 252 to step 256 described above, the final collection using the graphics processor at a given point of view (

By repeating these steps for all visible points, or using caching methods, we can effectively generate indirect lighting information for all pixels.

)에 의한 효과를 계산하는 과정(도 2의 단계 270에 해당됨)을 설명한다. 도 6은 본 발명에 따른 렌더링 방법 중 비확산 반사 광휘(

)의 효과를 계산하는 과정을 순차적으로 도시한 흐름도이며, 도 7은 비확산 반사 광휘의 계산 과정을 설명하기 위하여 도시한 도면이다. 도 7에 있어서, 투영하고자 하는 비난반사 포톤 p가 저장된 3차원 공간상의 지점

에 대하여

는 법선 방향,

는 포톤 p에 대한 사각형이 이미지 평면에 투영되었을 때 영향을 미치는 특정 픽셀에서 보이는 실제 물체위 지점,

는 포톤 p가 저장된 지점

와 투영된 특정 픽셀에서 보이는 실제 지점

사이의 거리를 의미한다.Hereinafter, with reference to FIGS. 6 and 7, the non-diffuse reflective brightness of the indirect lighting effect according to the present invention (

), A process of calculating an effect by () corresponds to step 270 of FIG. 2). 6 is a view illustrating non-diffuse reflection luminance of a rendering method according to the present invention;

FIG. 7 is a flowchart sequentially illustrating a process of calculating an effect of FIG. 7, and FIG. 7 is a diagram illustrating a process of calculating a non-diffuse reflection luminance. 7, the point on the three-dimensional space in which the non-reflective photons p to be projected are stored

about

The normal direction,

Is the point on the actual object visible at a particular pixel that affects when the rectangle for photon p is projected onto the image plane,

Is the point where the photon p is stored

And the actual point visible at the particular projected pixel

Means the distance between.

Referring to FIG. 6, first, by using luminance information of a non-diffusion photon map, quadrangles having sides of each photon having a length of twice the maximum kernel radius R previously set are contacted with a surface on which the photons are stored. And quadrature are first projected onto the image plane along the normal vector of the location where the corresponding photons are stored, via a rasterization operation of the GPU (step 272). The non-diffusion photon map is a photon map obtained by extracting and storing photons reflected from a surface having non-reflective BRDF using a photon mapping technique.

Next, the number of photons projected on each pixel constituting the image plane is measured, and the measured number of photons is stored as pixel information (step 274).

Next, the kernel radii for each photon are adjusted according to the ratio of the number of photons stored as pixel information to each pixel and the maximum number of photons affecting one preset pixel (step 276).

Next, using the photon mapping technique, the adjusted kernel radius in the process of reprojecting the quadrangle generated in step 272 to the image plane along the normal vector of the location where the photon is stored and calculating the kernel, is centered on each photon. By applying, the adaptive luminance information according to the distribution of the second projected photons is calculated.

Through the above-described process, the effect due to the non-diffuse reflective brightness of the indirect illumination according to the present invention is calculated. In order to calculate the effect due to the non-diffuse reflection brightness of the indirect illumination, both the incident point and the BRDF of the reflected point immediately before the incidence should be considered, and thus the calculation is not easy with the conventional final collection method. However, the method of calculating the effect by the non-diffusing reflected light according to the present invention can effectively generate non-diffusion indirect illumination by projecting the non-diffusion photon map onto the image plane using a graphics processor.

As described above, the method for calculating the effect due to the non-diffuse reflection luminance according to the present invention is to input the visual point information for all the pixel samples to the GPU in the form of a texture and perpendicular to the normal of the three-dimensional object point where each non-diffusion photon is stored. The photon information is converted into a rectangular shape and drawn, and projected onto the image plane. At this time, the information possessed by each photon is put in the form of texture coordinates at each vertex of the rectangle so that the fragments generated during the rasterization process can be projected with the same information. In the pixel shader, the interpolation kernel is calculated by using the visible information of the projected pixel and the photon information of the fragment to calculate the brightness of the photon affecting the pixel. In general, when using the photon mapping technique, the distribution of stored photons is often non-uniform, depending on the nature of the scene. Therefore, in areas with few photons, use a sufficient kernel radius to produce smooth radiance. The method of reducing the detail is used. However, for projection methods where the total number of photons affecting one pixel is not known until the end of the process, an adaptation that dynamically adjusts the kernel radius in the middle of the calculation using both the kernel radius and the number of photons is used. No kernel application is possible. Unlike conventional techniques that used inflexible kernel radii or complex data structures for adaptive applications, this technique applies dynamic kernel radii using a simple extension that projects two photons. In the first projection, the initial kernel radius defined by the user is used to calculate the number of photons that affect the pixel by accumulating the number of times instead of the luminance information at each pixel for the projected photons, and in the second projection, the maximum defined by the user. The kernel radius is readjusted by the ratio of the number of photons to the number of photons that have an actual effect calculated in the first projection, allowing for adaptive calculation by the number of photons by not calculating photons outside the newly calculated radius in the pixel shader. In this way, it is possible to preserve the fine luminosity in areas with high photons and to produce smooth luminosity in areas with low photons.

Although the present invention has been described above with reference to preferred embodiments thereof, this is merely an example and is not intended to limit the present invention, and those skilled in the art do not depart from the essential characteristics of the present invention. It will be appreciated that various modifications and applications which are not illustrated above in the scope are possible. And differences relating to such modifications and applications should be construed as being included in the scope of the invention as defined in the appended claims.

The rendering method according to the present invention can be used in non-real time applications such as movies or 3D animations, but not real time applications such as games.

1 is a structural diagram illustrating hierarchically divided rendering equations in a rendering method for global illumination processing according to a preferred embodiment of the present invention.

FIG. 2 is a flowchart sequentially illustrating a rendering method for indirect lighting processing according to the present invention, and FIG. 3 is a conceptual diagram for describing an illumination processing by an indirect light source incident on a nonspecular surface according to the present invention. It is shown as.

)에 의한 효과를 계산하는 과정을 순차적으로 도시한 흐름도이며, 도 5는 확산 반사 광휘의 계산 과정을 설명하기 위하여 도시한 도면이다.4 is a diffuse reflection luminance of a rendering method according to the present invention;

FIG. 5 is a flowchart sequentially illustrating a process of calculating an effect of FIG. 5, and FIG. 5 is a diagram illustrating a process of calculating diffuse reflection luminance.

)의 효과를 계산하는 과정을 순차적으로 도시한 흐름도이며, 도 7은 비확산 반사 광휘의 계산 과정을 설명하기 위하여 도시한 도면이다. 6 is a view illustrating non-diffuse reflection luminance of a rendering method according to the present invention;

FIG. 7 is a flowchart sequentially illustrating a process of calculating an effect of FIG. 7, and FIG. 7 is a diagram illustrating a process of calculating a non-diffuse reflection luminance.

Claims (7)

In the rendering method for the indirect lighting effect, (a) receiving information about a scene to be rendered; (b) generating visibility point information by performing a visibility check on the scene; (c) generating global photon maps and non-diffusion photon maps containing approximated luminance information using photon mapping techniques; (d) Diffuse reflectance luminance for all visible points using the global photon map;

Calculating the effect of; (e) Using the non-diffusion photon map, the non-diffuse reflectance luminance (

Calculating the effect of; It is provided, the diffuse reflection light (

) Is the luminance reflected by the diffuse BRDF at the point y left just before the photon enters the visible point (x), and the non-diffuse reflectance luminance (

) Is the luminance reflected by the non-diffuse BRDF at the point y left just before the photon enters the visible point x, Step (d) (d1) rendering the global photon map on each face of the semi-hexahedron for one visible point to generate a semi-hexahedron including luminance information coming in the hemispherical direction with respect to the visible point; (d2) generating a direction map by sampling the hemisphere direction using the BRDF information on the visible point; (d3) loading the direction map for the visible point to sample the semi-hexahedral map for the visible point, and adding the sampled luminance information to calculate 1 × 1 pixels; (d4) repeating steps (d1) to (d4) for all visible points to calculate 1 × 1 pixels for all visible points; Rendering method for the indirect lighting effect, characterized in that it comprises a. delete The method of claim 1, wherein step (e) (e1) using the non-diffusion photon map, a figure having a side length of twice the preset maximum kernel radius R around each photon is formed, and the figures are normals of the positions where the corresponding photons are stored. Primary projection along the vector to the image plane; (e2) measuring the number of photons primarily projected on each pixel constituting the image plane and storing the number of photons as pixel information of the corresponding pixel; (e3) adjusting kernel radii for each photon according to the number of photons stored as pixel information in each pixel; And (e4) accumulating luminance information on each pixel by applying the adjusted kernel radius in the process of reprojecting the figure generated in (e1) to an image plane around each photon and calculating a kernel; Rendering method for the indirect lighting effect, characterized in that it comprises a. In the rendering method for calculating an indirect lighting effect using a graphics processor (GPU), (a) receiving information about a scene to be rendered; (b) generating visibility point information by performing a visibility check on the scene; (c) generating a global photon map containing approximated luminance information using photon mapping techniques; (d) rendering the global photon map on each face of the semi-hexahedron for one visible point to generate a semi-hexahedron including luminance information coming in the hemispherical direction with respect to the visible point; (e) sampling a hemisphere direction using the BRDF information for the visible point to generate a direction map; (f) loading the direction map for the visible point to sample the semi-hexahedral map for the visible point and summing the sampled luminance information to calculate 1 × 1 pixels; (g) repeating steps (d) to (f) for all visible points and calculating 1 × 1 pixels for all visible points, respectively; Diffuse reflectance luminance, which is the luminance reflected by the diffuse BRDF at the point y left just before the photon enters the visible point x,

Rendering method for the indirect lighting effect, characterized in that for calculating the indirect lighting effect. 5. The rendering method of claim 4, wherein summing up the luminance information sampled in the step (f) uses a mipmap operation. In the rendering method for calculating an indirect lighting effect using a graphics processor (GPU), (a) receiving information about a scene to be rendered; (b) generating visibility point information by performing a visibility check on the scene; (c) extracting photons reflected from the surface having the non-reflective BRDF using photon mapping technique, and generating a non-diffusion photon map using the extracted photons information; (d) using the non-diffusion photon map, form a figure having a side length of twice the preset maximum kernel radius R about each photon, and normalizing the figures at the location where the corresponding photon is stored. Primary projection along the vector to the image plane; (e) measuring the number of photons projected primarily on each pixel constituting the image plane and storing the number of photons as pixel information of the corresponding pixel; (f) adjusting kernel radii for each photon according to the number of photons stored as pixel information in each pixel; (g) accumulating luminance information on each pixel by applying the adjusted kernel radius in the process of reprojecting the figure generated in (d) onto an image plane around each photon and calculating a kernel; Non-diffuse reflectance luminance, which is a luminance reflected by a non-diffuse BRDF at a point y that leaves the photon just before entering the visible point (x);

Rendering method for the indirect lighting effect, characterized in that for calculating the indirect lighting effect. 7. The method of claim 6, wherein the step (f) adjusts the kernel radii for each photon according to a ratio of the number of photons stored as pixel information in each pixel and the maximum number of photons affecting a preset pixel. Rendering method for indirect lighting effect, characterized in that.

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