Timeline for Rasterization: How does hardware disambiguate identical Z values at silhouette edges?
Current License: CC BY-SA 4.0
8 events
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| Apr 10, 2021 at 14:03 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Mar 16, 2021 at 14:05 | comment | added | Simon F | This would appear to be a related question: computergraphics.stackexchange.com/q/3619/209 | |
| Mar 13, 2021 at 19:07 | comment | added | Nathan Reed | I guess there could be some extra rule like that, but I've never heard of it; nor can I find anything like that in either the Direct3D or OpenGL rasterizer and depth-test specs. There's no hint in there of any interaction between face orientation and either rasterization rules or depth testing. Honestly I think in practice we almost always have backface culling enabled and so in most use cases / engines you would not see this problem. I would test it directly but my home codebase isn't well set-up to do that right now. | |
| Mar 13, 2021 at 1:46 | comment | added | geometrian |
@NathanReed I thought of that; I think there must be some sort of exception for submission order here. Consider <. If fragments from later indices lose, then we could get the wrong fragment on edges just by having the front triangle happen to render after the back triangle. This would expose the problem in most engines just by rotating the model around.
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| Mar 11, 2021 at 18:13 | comment | added | Nathan Reed | Doesn't this just fall back to triangle submission order, i.e. whichever triangle was later in the index buffer wins, for depth functions that include "equals", and whichever was earlier wins, for depth functions that don't include "equals"? GPUs are required to respect submission order in terms of the final contents of the framebuffer, even if they process things in parallel and out-of-order along the way through the pipeline. It's a similar case to rendering transparent objects back-to-front, with depth writes disabled. | |
| Mar 11, 2021 at 13:14 | answer | added | pmw1234 | timeline score: 1 | |
| Mar 11, 2021 at 3:17 | answer | added | Nicol Bolas | timeline score: 0 | |
| Mar 11, 2021 at 2:45 | history | asked | geometrian | CC BY-SA 4.0 |