Reflections missing in chrome object

[Alex_M]

Sorry for all the thread spamming lately but it's the first time that I delve deeper in RT CUDA rendering, and by using it in a real production environment I find lots of things that I need help with understanding.

In this particular one, there's a scene where I noticed that the reflections in the chrome object are missing. The light on the floor is so strong that it certainly looks unnatural for the chrome to not pick them up. Sure enough, when I switched to Adv the reflections appeared! Is RT just incapable of many reflection bounces or am I missing something? I can see the proper reflections during the Light Cache calc. phase but then they disappear when the rendering starts.

I'm using default RT settings apart from setting Trace Depth to 15. Also, all materials have reflection and refraction depth of 15. Apart from Trace Depth, I couldn't find any other setting in RT that would relate to the number of reflection bounces.

Here's a screenshot:

[vlado]

Does it get better if you turn up the "max ray intensity" parameter?

Best regards,
Vlado

[Alex_M]

Thanks for the suggestion. I had to turn MRI all the way up to 1000000.0 and it almost matches the Adv render now. But now the whole room is blown out waaaay brighter than the Adv render (check screenshot below).

I think it's a bit strange that I need to set MRI to such extreme number for the reflection to come up correctly. It comes up correctly with MRI of just 20 in Adv. Could the problem be coming from the Directional parameter of the Vray disc light? Maybe related to this problem?

[vlado]

It could be related. Will have to look into it.

Best regards,
Vlado

[Alex_M]

I'm wondering if there's any update on this? I'm working on a scene now lit entirely by just an HDRI dome where RT again seems to either miss reflections completely or render them darker than Adv with the same material and render settings. So it seems the issue is not related to the directionality parameter.

Please check the image below. Notice how the Adv and RT images are identical everywhere except for the reflections in the glass of the sliding doors. With RT there are less reflections (some are even missing) and weaker lighting on the planks and sofa. Let me know if you need the scene and I'll send it.

Even if I increase refl/refr depth of all materials to 30, it doesn't do much to help. I also tried setting Trace depth to 30, Override depth to 30, GPU textures to "Full-size textures" and Texture format to "Float" but it was still pretty much the same. As a last resort I tried increasing Max ray intensity from 20 to 100 but it didn't help much either. It recovered most of the missing reflections but the areas that were darker didn't improve and the areas that were actually fine became brighter and overexposed.

I love the faster render speeds of RT, but this problem stops me from confidently using it in more complex scenes like interiors and exteriors since I'm afraid RT will show dark (or missing) reflections in reflective objects and less lighting than in reality. In interior scenes it's really important that the lighting and reflections behave as naturally as possible and that they are not missing or dark.

[vlado]

Can you post that part of the scene or email to me at vlado@chaosgroup.com so that I can look into it?

Best regards,
Vlado

[Alex_M]

Scene sent!