bidirectional, highly reflective mats (metals) render pure black

[Juraj]

I've been trying the bidirectional, but in every mode I tried (Bidi pathtracing, VCM,..) it seems materials that I have high fresnel number on (40), eg my metals, mirrors, render pure black in color.
The scene is lit by HDR and portal lights.
I can't seem to find anything much about bidirectional mode searching the forum. Anyone can share some light :- ) ?

[lacilaci]

A screenshot and maybe some overview on the situation might help. You have this only when using high fresnel? If you lower IOR value then it's okay?.. However:

Try to increase max ray depth from 25 to max (100) exit color is black by default

Make sure you don't use black color as diffuse, try rgb2,2,2

also check if you haven't accidentaly turned on reflections override in render settings (default color is black)

I tried to replicate it but unless I use hdri with fully black areas and material with completely black 0,0,0, diffuse . I won't get pure black areas....

[Ondra]

yep, a scene would be appreciated ;)

Aren't you using for example blend materials?

[Juraj]

2Keymaster: That's it ! Not at the office at the moment but you are correct, all my metals are blended, even when off during current scene (it doesn't blend them same way as I am used to from Vray but I kept it anyway). Thank you ! Where can I educate myself more about bidir in Corona ? Searching fails me

2Laci, thanks to this :- ) I probably should have stated the scene renders completely correct otherwise. I don't change stats or mats into dumb state. It only occurred when I switched to bidir mode.

I am sorry about the lack of screenshot and scene, but I thought this would be fairly simple scenario from description. It indeed was :- )

[Ondra]

ok, this is known limitation of my bidir implementation. I won't fix it unless bidir proves superior to PT in most scenes