mandrake0
houdini-17.5.239-win64-vc141.exe

Houdini -> product name
17 -> mature version
.5 -> minor version
.239 -> daily build number (release)
Win64 -> operating system windows 64bit
vc141 -> microsoft compiler version
.exe -> executable for windows systems

I think there is also a description somewhere on the internet.

dlee

jerry7
Thank you for reply. I want to know why PBR Reflecton and PBR Refraction is ok? What different between them and reflected/refracted light vop? Are they both BSDFs?

Reflected/refracted Light VOPs can output BSDF (“f” output, either cone or specular depending on parameters). PBR Reflection/Refraction VOPs are more modern and give you a lot more options. They also have constant albedo unaffected by builtin fresnel (for better or worse - better, in this case), so when you add both together, they each get 50/50 chance of being sampled by the light.

tamte
to me it always felt like a bug or at least a big limitation of direct lighting that makes rendering clean glass like surfaces very painful

it seems to me that forcing at least one sample per brdf per pixel no matter how low the probability is would solve this

as in the above example, if you make even mix of both brdfs 50/50 it's still noisy even with 6*6 samples (with or without ray variance)
while in old school shaders having 1 reflection and 1 refraction sample would be super clean straight away

but honestly 36 samples with 50/50 chance has no reason to be noisy for 2 perfectly specular lobes

dlee
It's not a bug, it's an unfortunate consequences of having 2 bsdfs stacked together. Direct lighting chooses which bsdf to evaluate based on their albedo. The reflection contribution (“kr”) from fresnel is only about 2~3% of the combined contribution (in the circled region), so the vast majority of the lighting samples are reserved for refraction and not enough is left over for reflection.
The recommended solution for such case is to increase shading quality on the light, but there are other workarounds. e.g. add PBR Reflecton and PBR Refraction vops together (with fresnel blend enabled on the bsdfs).

awesomedata
Is this really still not possible in Houdini 17.5?

twod
Manipulate tends to be populated with SOPs that can be adjusted in the viewport easily, while Utility contains nodes that do control flow, complex operations (wrangles), or very “mathy” types of things.