I once used projections on 4 sides tetrahedron for my shadow mapping needs (one shadow map for all cases for simplicity reasons).
This, of course, requires 4 projection matrices that target specific part of the texture + clipping planes. PCF works if you use rays (and dinamically determine which triangle is affected). Hope this helps.
Why not use two parabolic shadow maps for point lights? You can use the filtering methods you would normally be able to use for directional shadows.
http://graphicsrunner.blogspot.com/2008/07/dual-paraboloid-shadow-maps.html
I imagine you might even be able to render to it with one pass using a geometry shader too.
Thoughts?
PCF filtering over dual paraboloids is non-trivial to say the least. Although the curvature of the results could yield softening with fewer block-shaped artifacts (Poisson sampling is often used to get around this), the density of the pixels changes depending on how far away from the center you are, so you would effectively be sampling close-together shadow points near the center and farther-away points near the edges.
Ultimately I was wrong about the type of filtering we wanted to do to the shadows—we did at one point want to use anti-aliasing with VSM shadows, but because of the large gap between our near and far planes there were too many artifacts.
We are sticking to PCF, which has hardware support for blending 4 shadow samples at a time but we need more than that.
Since this is a run-time sampling set we need to be able to manually sample left, right, up, and down from the center texel, so we need to sample into the cube texture manually. Otherwise we would need to calculate in spherical coordinates where the neighboring texels are which would be incredibly slow, especially since PlayStation 4 and Xbox One have intrinsics to calculate where to sample on cube textures. Sampling a cube texture natively outputs these same intrinsics once for each sample, whereas by manually using the intrinsics we can reuse their results and create the absolute minimal code for the multiple samples we need.
Simply drawing the cube texture’s faces to a single 2D texture would not help reduce this complexity, but it helps us shift towards texture atlases for shadows which will in the end allow us to apply all the shadows in our scene in one pass.
L. Spiro
Ultimately I was wrong about the type of filtering we wanted to do to the shadows—we did at one point want to use anti-aliasing with VSM shadows, but because of the large gap between our near and far planes there were too many artifacts.
You can try MSM shadow mapping which is the last tech on variance shadow mapping. But it still have bleeding on certains cases.
Simply drawing the cube texture’s faces to a single 2D texture would not help reduce this complexity, but it helps us shift towards texture atlases for shadows which will in the end allow us to apply all the shadows in our scene in one pass.
You will render all shadow map in a texture2D atlas, uses it to draw deferred shadow using a fullscreen quad then render deferred lighting on it ?
My coworker showed me a video on it yesterday. That will be a goal for the future. According to the video he showed me, PCF was running at 400 FPS and MSM was running at 500-550 (and with fewer artifacts). That’s a separate task I will propose in the future.You can try MSM shadow mapping which is the last tech on variance shadow mapping. But it still have bleeding on certains cases.
Our current implementation has to make 2 passes to render shadowed lights (and my description of it may be wrong—I only know roughly how that part of the engine works): One to apply shadows to the stencil buffer and then again to add lighting. Yes, deferred. Yes, we will be able to merge all of the shadows into the same pass as lighting if all the shadows are in a single texture.You will render all shadow map in a texture2D atlas, uses it to draw deferred shadow using a fullscreen quad then render deferred lighting on it ?
My coworker showed me a video on it yesterday. That will be a goal for the future. According to the video he showed me, PCF was running at 400 FPS and MSM was running at 500-550 (and with fewer artifacts). That’s a separate task I will propose in the future.
According to MJP, moving to MSM is very straightforward, should not take long time.
That’s fine.According to MJP, moving to MSM is very straightforward, should not take long time.
There's an upcoming article on this topic in GPU Pro 6 btw: http://hd-prg.com/tileBasedShadows.html
(Code included...if you want to dig into that)
There's an upcoming article on this topic in GPU Pro 6 btw: http://hd-prg.com/tileBasedShadows.html
(Code included...if you want to dig into that)
Looks very interesting. Would be nice to see a comparison between this and http://www.cse.chalmers.se/~olaolss/main_frame.php?contents=publication&id=clustered_with_shadows_siggraph_2014
My coworker and a guy from AMD are going to release a paper soon which I is a significant improvement on—I believe—this. Many times higher quality and many times faster.There's an upcoming article on this topic in GPU Pro 6 btw: http://hd-prg.com/tileBasedShadows.html
(Code included...if you want to dig into that)
Looks very interesting. Would be nice to see a comparison between this and http://www.cse.chalmers.se/~olaolss/main_frame.php?contents=publication&id=clustered_with_shadows_siggraph_2014
