Sampling shadow maps at an offset
Disclosed herein is a web-based videoconference system that allows for video avatars to navigate within a virtual environment. Various methods for efficient modeling, rendering, and shading are disclosed herein.
1. A computer-implemented method for efficiently rendering shadows in a three-dimensional virtual environment, comprising:
rendering a shadow map of at least a portion of the three-dimensional virtual environment from a perspective of a light source in the three-dimensional virtual environment, the shadow map specifying a plurality of distances from the light source to objects of the three-dimensional virtual environment with navigable video avatars;
rendering an image of the three-dimensional virtual environment from a perspective of a virtual camera;
for respective pixels of the image:
identifying a point in the three-dimensional virtual environment such that the point is offset from a position in the three-dimensional virtual environment depicted in a pixel by a first offset value from the position in a normal direction with respect to a ground of the three-dimensional virtual environment and a second offset value in a direction toward the light source from the position;
selecting, from the shadow map, a first distance according to the identified point;
determining a second distance from the identified point to the light source; and
when the second distance exceeds the first distance, shading the respective pixel.
2. The method of claim 1 , wherein the first and second offset values are selected to prevent shadow acne.
3. The method of claim 1 , wherein the selecting comprises selecting, from the shadow map, a plurality of first distances of pixels in the shadow map surrounding the point, and
wherein the shading comprises shading the respective pixel to a degree corresponding to how many of the plurality of first distances do not exceed the second distance.
4. The method of claim 3 , wherein the plurality of first distances are selected in a pattern at an angle offset from a ground of the three-dimensional virtual environment.
5. The method of claim 4 , wherein the pattern is a rotated square pattern.
6. The method of claim 4 , wherein the angle is selected to soften shadows.
7. The method of claim 1 , further comprising presenting the rendered image to a first participant to a conference, wherein the virtual camera is navigable within the three-dimensional virtual environment by the first participant.
8. The method of claim 7 , wherein the three-dimensional virtual environment includes a representation of a second participant to the conference, the representation being navigable within the three-dimensional virtual environment by the second participant and having mapped thereto video captured of the second participant.
9. A computer-readable non-transitory storage medium comprising instructions which, when executed by a computer, cause the computer to carry out operations for efficiently rendering shadows in a three-dimensional virtual environment, the operations comprising:
rendering a shadow map of at least a portion of the three-dimensional virtual environment from a perspective of a light source in the three-dimensional virtual environment, the shadow map specifying a plurality of distances from the light source to objects of the three-dimensional virtual environment with navigable video avatars;
rendering an image of the three-dimensional virtual environment from a perspective of a virtual camera; and
for respective pixels of the image:
identifying a point in the three-dimensional virtual environment such that the point is offset from a position in the three-dimensional virtual environment depicted in a pixel by a first offset value from the position in a normal direction with respect to a ground of the three-dimensional virtual environment and a second offset value in a direction toward the light source from the position;
selecting, from the shadow map, a first distance according to the identified point;
determining a second distance from the identified point to the light source; and
when the second distance exceeds the first distance, shading the respective pixel.
10. The computer-readable non-transitory storage medium of claim 9 , wherein the first and second offset values are selected to prevent shadow acne.
11. The computer-readable non-transitory storage medium of claim 9 , wherein the selecting comprises selecting, from the shadow map, a plurality of first distances of pixels in the shadow map surrounding the point, and
wherein the shading comprises shading the respective pixel to a degree corresponding to how many of the plurality of first distances do not exceed the second distance.
12. The computer-readable non-transitory storage medium of claim 11 , wherein the plurality of first distances are selected in a pattern at an angle offset from a ground of the three-dimensional virtual environment.
13. The computer-readable non-transitory storage medium of claim 12 , wherein the pattern is a rotated square pattern.
14. The computer-readable non-transitory storage medium of claim 12 , wherein the angle is selected to soften shadows.
15. The computer-readable non-transitory storage medium of claim 9 , further comprising presenting the rendered image to a first participant to a conference, wherein the virtual camera is navigable within the three-dimensional virtual environment by the first participant.
16. The computer-readable non-transitory storage medium of claim 15 , wherein the three-dimensional virtual environment includes a representation of a second participant to the conference, the representation being navigable within the three-dimensional virtual environment by the second participant and having mapped thereto video captured of the second participant.