4 ms·

> The current raytracing acceleration is intended to boost some highlights and shadows in practice. A couple of days ago, while gaming with a few friends and n

> The current raytracing acceleration is intended to boost some highlights and shadows in practice. A couple of days ago, while gaming with a few friends and noticing a transparency ordering issue in the game we played and explaining to them, how and why that happens I realized something: The raytracing accelerators we now have at our disposal can also be used to implement proper primitive level transparency ordering on the GPU; even if you don't spawn secondary rays, just being able to do a sparse ray-triangle hit test through the whole scene building the render order list in situ.

Impossible 6y ago
Unfortunately it's still extremely expensive to do so. DXR documentation tells you to keep any hit shaders simple. It's also possible to fix transparency ordering in rasterization using OIT and there is some hardware support for it (ROV), but it's also expensive and can be hard to do right so many games choose rough sorting
DavidVoid 6y ago
Transparency is still very expensive unfortunately. DICE spoke about it a GDC talk last year and recommended that the any hit shaders that are used for alpha testing (i.e., transparency) should be avoided if possible since they're rather expensive. Their big problems is trees, since leaves modeled as flat squares with their the actual leaf shapes in textures (that are completely transparent around the leaves). "Trees are our biggest problem in ray tracing. No matter what we do they're by far the slowest thing to trace, and they're much worse than on rasterizer, and if you have any ideas of how to ray trace trees efficiently, we're very happy to hear them. We've asked a lot of very smart people and no one has come up with a good answer yet. You can choose between geometry and alpha testing and both are kinda crap." - It Just Works: Ray-Traced Reflections in 'Battlefield V', GDC 2019.

Impossible 6y ago

Unfortunately it's still extremely expensive to do so. DXR documentation tells you to keep any hit shaders simple. It's also possible to fix transparency ordering in rasterization using OIT and there is some hardware support for it (ROV), but it's also expensive and can be hard to do right so many games choose rough sorting

DavidVoid 6y ago

Transparency is still very expensive unfortunately. DICE spoke about it a GDC talk last year and recommended that the any hit shaders that are used for alpha testing (i.e., transparency) should be avoided if possible since they're rather expensive. Their big problems is trees, since leaves modeled as flat squares with their the actual leaf shapes in textures (that are completely transparent around the leaves). "Trees are our biggest problem in ray tracing. No matter what we do they're by far the slowest thing to trace, and they're much worse than on rasterizer, and if you have any ideas of how to ray trace trees efficiently, we're very happy to hear them. We've asked a lot of very smart people and no one has come up with a good answer yet. You can choose between geometry and alpha testing and both are kinda crap." - It Just Works: Ray-Traced Reflections in 'Battlefield V', GDC 2019.