How I can control the GI multiple-bounce in VRay?

[doark]

I have this question a some time, but even reading the documentation and learning from tutorials I still do not quite understand how this works in VRay.

When I used the Mental Ray with only FG, It was just me increase the field "Secondary Diffuse Bounces" for a number greater than 0 (zero) to I have control of how multiple-bounce will be calculated.

But VRay has split the Primary and Secondary bounces! I understand that if I use only the Primary Engine in VRay would be equivalent to FG 0 Secondary Bounces (or single bounce only) with MR. But in VRay to have the Secondary bounces I have 3 options: Photon map, Brute Force and Light cache.

In my test when I use Photon map or BF I can control how many bounces are calculated, so if I want more illumination in my scene it's only increase the number of Bounces/Depth (PM/BF) correct But how do I do the same thing in a combination involving LC?

For example: With BF+LC how I do to increase the number of bonces to improve the illumination of the scene?! (What I've been doing so far is connect the VRayPhysicalCamera and go increasing the exposure!) I feel the same confusion when I use IM+LC too.

Thanks for your patience in understanding my question!

[Morbid Angel]

LC is set to have 100 bounces by default you cold see that option in the lc section, its really fast anyway so o need to work with bounces.

[doark]

Interesting! Thanks for answering x)
I tested is actually how you said Morbid Angel. But my goal is not to diminish the number of bonces but raise! When I digit a number greater than 100 in the field Depth of LC is not possible to enter a number of bounces greater than 100.

Is there any way to further increase the illumination coming from the the GI in a scene?

[joconnell]

Light cache will use as many bounces until the bounces aren't making all that much difference anymore, for example if light cache has done 12 bounces of light and bounce 13 will only make it 0.01% brighter, it'll probably stop at that stage. For you to get the same brightness with photon mapping or brute force (especially in interiors) you'd have to use a lot of bounces! If you want your GI to be brighter, either make the lights brighter, make the materials of the objects in the scene brighter or turn up the GI multiplier in the section of the render dialog that you choose your primary and secondary engine. I'd advise not doing that since it'll break the realism of the lighting so I'd look at the other factors making your render dark.

[doark]

It's been awhile since I started this topic, but I have a doubt that allows having a continuation in this topic. Thanks Joconnell, for the clarification of how the bounces mechanism works the Light cache!

I see in many Pixar's films a lovely effect , which I believe to be an effect of: Bounce of light (I mean Indirect Light). The effect I am saying is this:
http://dl.dropboxusercontent.com/u/3...footindoor.gif

http://dl.dropboxusercontent.com/u/3...rman-point.gif

Well, the only way I could get "close" to that effect in VRay was using a VRayOverrideMtl -> GI material assigned to a VRayMtl. But it seems that breaks all the energy distribution function of VRay and my feeling of "physically correct illumination" disappears.

I am losing something in VRay or it is not possible to be done using the tools in VRay?
Thanks for attention!

[vlado]

The pixar images have just one single bounce of color bleeding; this would be equivalent to setting the secondary GI engine to "None" in V-Ray.

Best regards,
Vlado

[Morbid Angel]

It's been awhile since I started this topic, but I have a doubt that allows having a continuation in this topic. Thanks Joconnell, for the clarification of how the bounces mechanism works the Light cache!

I see in many Pixar's films a lovely effect , which I believe to be an effect of: Bounce of light (I mean Indirect Light). The effect I am saying is this:
http://dl.dropboxusercontent.com/u/3...footindoor.gif

http://dl.dropboxusercontent.com/u/3...rman-point.gif

Well, the only way I could get "close" to that effect in VRay was using a VRayOverrideMtl -> GI material assigned to a VRayMtl. But it seems that breaks all the energy distribution function of VRay and my feeling of "physically correct illumination" disappears.

I am losing something in VRay or it is not possible to be done using the tools in VRay?
Thanks for attention!

There is nothing difficult about achieving the effect in the gifs you've demonstrated. Please see attached images. First render just direct light, second, direct light + brute force as primary bounce, third brute force + lightcache.

gi_Example.zip