3 ms·

I didn't get it either, I found this though which seems to be a much better fundamentals of radiance cascades: https://mini.gmshaders.com/p/radiance-cascades ht

by rendaw 2y ago

I didn't get it either, I found this though which seems to be a much better fundamentals of radiance cascades: https://mini.gmshaders.com/p/radiance-cascades https://mini.gmshaders.com/p/radiance-cascades IIUC basically you have a quad/oct-tree of probes throughout the area of screen space (or volume of view frustum?). The fine level uses faster measurements, and the broad level uses more intensive measurements. The number of levels/fineness determines resolution. I guess for comparison: - Radiance cascades: complexity based on resolution + view volume; can have leakage and other artifacts - Ray tracing: complexity based on number of light sources, screen resolution, and noise reduction; has noise - RTX: ?? - Radiosity: complexity based on surface area of scene Also not sure, but I guess ray tracing + radiosity are harder to do in GPU?

arijo 2y ago
Thanks for the analysis and the insights - I guess I'll have to parse all of this a bite at a time :)
jasonjmcghee 2y ago
No octree/quadtree. It's just a stacked grid of textures, halving resolution (or otherwise reducing) each level. Low resolution layers capture many rays (lowest resolution say 4096 rays) and longer distances at lower spatial resolution. High resolution layers capture fewer rays (lowest say 4 rays) for shorter distances at high spatial resolution. When you merge them all together, you get cheap, soft shadows and a globally illuminated scene. In the post I wrote, I calculated it's similar in cost to firing 16 rays using a classic path tracer. But in theory should look similar to 4096 rays (or whatever the highest cascade layer does) but softer shadows. Depending on your approach the geometry of the scene is completely irrelevant. (Fixed step / DDA truly, JFA + DF has some dependence due to circle marching, but largely independent)

by rendaw 2y ago

arijo 2y ago

Thanks for the analysis and the insights - I guess I'll have to parse all of this a bite at a time :)

jasonjmcghee 2y ago

No octree/quadtree. It's just a stacked grid of textures, halving resolution (or otherwise reducing) each level. Low resolution layers capture many rays (lowest resolution say 4096 rays) and longer distances at lower spatial resolution. High resolution layers capture fewer rays (lowest say 4 rays) for shorter distances at high spatial resolution. When you merge them all together, you get cheap, soft shadows and a globally illuminated scene. In the post I wrote, I calculated it's similar in cost to firing 16 rays using a classic path tracer. But in theory should look similar to 4096 rays (or whatever the highest cascade layer does) but softer shadows. Depending on your approach the geometry of the scene is completely irrelevant. (Fixed step / DDA truly, JFA + DF has some dependence due to circle marching, but largely independent)