Global illumination using shared lighting contributions for interactions in path tracing
Disclosed approaches provide for interactions of secondary rays of light transport paths in a virtual environment to share lighting contributions when determining lighting conditions for a light transport path. Interactions may be shared based on similarities in characteristics (e.g., hit locations), which may define a region in which interactions may share lighting condition data. The region may correspond to a texel of a texture map and lighting contribution data for interactions may be accumulated to the texel spatially and/or temporally, then used to compute composite lighting contribution data that estimates radiance at an interaction. Approaches are also provided for reprojecting lighting contributions of interactions to pixels to share lighting contribution data from secondary bounces of light transport paths while avoiding potential over blurring.
1. A method comprising:
determining a first lighting contribution of a first secondary ray to a first light transport path, the first lighting contribution being a first sample of radiance at a first surface point of a virtual environment;
determining a second lighting contribution of a second secondary ray to a second light transport path, the second lighting contribution being a second sample of radiance at a second surface point of the virtual environment;
computing a value of radiance at the first surface point from the first sample of radiance and the second sample of radiance based at least on one or more characteristics of the first secondary ray and the second secondary ray; and
generating a rendered frame of the virtual environment using the value of radiance in computing lighting of the first light transport path.
2. The method of claim 1 , wherein the one or more characteristics include locations of the first surface point and the second surface point in the virtual environment and the computing is based at least on determining a similarity in the locations.
3. The method of claim 1 , wherein the one or more characteristics include hit distances of the first secondary ray and the second secondary ray.
4. The method of claim 1 , further comprising:
determining the first surface point falls within a texel corresponding to a texture map of a surface comprising the first surface point and the second surface point; and
determining the second surface point falls within the texel, wherein the value of radiance is computed using the first sample of radiance and the second sample of radiance based on the first surface point and the second surface point each falling within the texel.
5. The method of claim 1 , further comprising:
selecting a level of a mipmap based on the one or more characteristics of the first secondary ray; and
selecting the level of the mipmap based on the one or more characteristics of the second secondary ray, wherein the value of radiance is computed using the first sample of radiance and the second sample of radiance based on the level selected for the first secondary ray and the second secondary ray.
6. The method of claim 1 , wherein the first light transport path and the second light transport path are cast in a common state of the virtual environment.
7. The method of claim 1 , wherein the first light transport path and the second light transport path are cast in different states of the virtual environment, each state corresponding to a respective time and a respective rendering configuration of the virtual environment.
8. The method of claim 1 , wherein the first light transport path is cast through a first pixel of a virtual screen, and the method further comprises reprojecting the value of radiance at the first surface point to a second pixel in the virtual screen to determine lighting condition data of the second pixel.
9. The method of claim 1 , wherein the value of radiance represents irradiance.
10. A method comprising:
computing lighting contributions of secondary rays to a plurality of light transport paths, the lighting contributions being samples of radiance at surface points of a virtual environment;
storing groups of the lighting contributions, wherein a group of lighting contributions corresponds to radiance in a respective region in the virtual environment and a lighting contribution is stored in the group based on one or more characteristics of the lighting contribution being associated with the region; and
computing lighting of pixels associated with the light transport paths from the groups of the lighting contributions.
11. The method of claim 10 , wherein the lighting contribution is stored in the group based on a corresponding surface point being within the region.
12. The method of claim 10 , wherein the each of the plurality of light transport paths includes a different primary ray.
13. The method of claim 10 , wherein the group based is stored in a texel that corresponds to the region.
14. The method of claim 10 , wherein the group of lighting contributions are computed from a plurality of states of the virtual environment.
15. The method of claim 10 , wherein the computing of the lighting is by a light transport solver that uses the groups of the lighting contributions to spatially and temporally smooth solutions of the light transport solver.
16. A method comprising:
rendering a ray-traced image using one or more graphics processing units (GPUs), the rendering including determining, from lighting contributions of a plurality of secondary rays to a plurality of light transport paths, a value of radiance at an interaction in a light transport path in a virtual environment, the lighting contributions being samples of radiance at interactions of the plurality of secondary rays with the virtual environment.
17. The method of claim 16 , wherein the rendering the ray-traced image further includes determining a solution of a light transport solver for the light transport path using the value of radiance as an irradiance value for the interaction.
18. The method of claim 16 , wherein the each of the plurality of secondary rays corresponds to a different primary ray.
19. The method of claim 16 , wherein the rendering the ray-traced image further includes spatially and temporally smoothing a solution of a light transport solver for the light transport path using the value of radiance as an irradiance value for the interaction.
20. The method of claim 16 , wherein the light transport path corresponds to a first pixel for the ray-traced image, and the rendering the ray-traced image further includes reprojecting the value of radiance to a second pixel for the ray-traced image to determine a solution of a light transport solver for the second pixel.