5 ms·
The white furnace test
- Uriopass 3y agoI recently implemented a PBR renderer by following the learnopengl PBR tutorial. It doesn't pass the white furnace test. That made me realize I didn't understand much of the math I implemented. Random multiplications by pi and 2 as the author stated didn't work out.
- CyberDildonics 3y agoMost BRDFs that I have seen get darker as they get rougher like the article mentions. There are some that take into account the interreflections of the theoretical facets that make the distribution of normals that become the BRDF (mentioned in the link also), and they do better but I'm not sure even they pass this test straight up. Most of what is actually being used out there loses energy. Sometimes people have used a lookup table on top of the BRDF to compensate.
- pixelpoet 3y agoThe multi scattering BRDF/BSDFs do pass the furnace tests, as well as the newer hair BSDFs. I checked :)
- sokoloff 3y agoWhy “furnace” in the name of the test? I get the overall concept, but the name seems fairly arbitrary. Is it, or is there an anchor?
- mrob 3y agoThe inside of a hot furnace glows with the uniform illumination simulated by the test.
- mytailorisrich 3y agoThis is based on classic black body radiation experiments which use ovens/kilns/furnace. Here the concept is similar and the point is that the object is enclosed in a cavity that has an uniform emission spectrum, in this case white instead of black body.
- jxf 3y agoThe test is about being in a uniformly white-lit environment, like a very hot furnace. It's just a mnemonic.
- pixelpoet 3y agoSo weird to see this top of HN! Also there are actually two furnace tests, the other one is with 0.5 emission and 0.5 albedo, also should produce 1.0 +/- noise pixels. Greetz to all path tracing people <3
- yayitswei 3y agoI know the absolute minimum about ray tracing but could still follow the article. Kudos to the author for such clear, interesting writing.
- Severian 3y agoFunny enough this Youtube video presented itself to my feed the other day that goes over this very topic in the planned Blender 4.0 release. They have a new Multiscatter GGX function for BSDF. I think this goes a lot more in-depth and presents a lot of examples. https://www.youtube.com/watch?v=v6qXbV_Q7z4 https://www.youtube.com/watch?v=v6qXbV_Q7z4
- raldi 3y agoWhat’s the embedded ShaderToy supposed to look like? When I press play and wait, nothing happens for over a minute. This post would benefit greatly from a couple screenshots of failed tests.
- genewitch 3y agoit starts grey, then you see the outline of a sphere, background fades in, a red, blue, and white sphere appear around the central grey/white sphere, the scene fades back to grey, then the red and blue sphere come back and you can see the reflections or whatever on the central sphere, but you can't tell it's a sphere since it's "faded in to the background".
- arecurrence 3y agoI believe it requires webgl. Can you confirm whether your browser has webgl enabled?
- distract8901 3y agoBack in my day, a teapot in orbit around the sun was the best we had and we liked it
- boulos 3y agoLong ago, in https://graphics.stanford.edu/~boulos/papers/brdftog.pdf https://graphics.stanford.edu/~boulos/papers/brdftog.pdf we tried to trade off energy conservation and data reproduction at the cost of reciprocity. In the end, nobody actually cared about automatically fitting material data from BRDFs or if they do, they actually prefer a symmetric and conserving-enough BSDF, which is what most future research improved. In particular, breaking symmetry means making bidirectional path tracing and other techniques kinda weird.
- pixelpoet 3y agoHey look, it's Bouliiii from the ompf forums (RIP) :D Greetz, you might remember me as lycium :)