Vray Caustics causing light to become invisible to reflections

[Rob_Burns]

I was running some experiments with reflective caustics when I noticed an odd behavior. My test scene has one small area light shining onto a wavy chrome object which is then reflecting some caustics onto the floor. The small light is set to be visible and it is not hidden. When using PPT, BDPT or Vray RT the caustics show up on the floor AND the reflection of the light also shows up on the chrome object. But when I turn on vray caustics (photon mapped) and render the scene with IM/LC or Brute Force for GI suddenly the light is no longer visible in the chrome reflections. I was hoping to start adding reflective caustics into my renderings using the photon mapped caustics, but obviously don’t want to loose control over which lights are visible in reflections. Examples below:

Vray RT (I think this is correct, caustics and light source are visible in chrome reflection).

BDPT (note that the light is visible in the chrome reflection, but the caustics on the floor are not).

PPT (light and caustics visible in reflection, caustics very noisy, but only ran for 3.5 min, with time noise would probably would clean up)

IM / LC with vray caustics (note light source is not visible in reflection)

Brute Force GI with vray caustics (again light source not visible in reflection).

So I guess my question would be is there some setup that allows me to use vray caustics without loosing the reflection of light sources?

[vlado]

It looks either like a bug, or like a limitation; but you can always precalculate the photon map, save it, and then turn caustics off for the light.

It is interesting that the GPU handled this best

Best regards,
Vlado

[svetlozar.draganov]

Hello,

Can you provide this scene , and inform us about Vray and Max versions you are using.
Here is the result of my tests - the reflection of the light is visible in the chrome object.

caustics.zip (31.3 KB)

[Rob_Burns]

sure, I just emailed the scene to support@chaosgroup.com, is that the best way to get it to you? Software versions are Max 2012 and Vray 2.45.01. And yes RT GPU is very fun to use, the new CUDA option is great.

[svetlozar.draganov]

Thank you very much for your feedback and the scene.
We managed to reproduce the issue - it seams that the problem is not with reflection of the light but with specular, and it only happens if Plane Light is used.
The issue doesn’t occur if Vray Sphere light or any other Vray Light is used instead of Plane.
As a workaround you can use either Sphere Lights or you can use Vray Mesh light and assign simple plane object into it - it will work just like Vray Plane Light.
We will update you as soon as we have a solution to this issue.

[Rob_Burns]

Thanks for the reply, mesh lights will work just fine for me for now, appreciate the help!