GI and displacements,... can GI be turned off?

[Pongo]

I'm wondering if there is a way to render GI with displacement, but to have VRay not calculate the GI of the displaced mesh, but rather the non-displaced mesh.

I would like to be able to do this all in one pass as well,... so that rules out any possibilities like pre-computing the GI solution,... plus there are moving objects that would affect things.

I have a scene that I like the settings on with GI, and adding displacement looks incredible, but I cannot afford the lengthy rendertime associated by having both active at the same time. (right now I can either do only GI, or only displacement)

thanks

[RErender]

As of now this is not possible, though if it works with your scene turning off "generate GI" will be quite a bit faster.

[Pongo]

ok thanks for the response.

Unfortunately I need to include the object in the GI solution,... (it is a ground plane) the displacement was being used for nice pebble and rock details (which is why I really don't care if they are part of the overall solution.

Oh well,... back to work

[davexl23]

A solution

Just thinking aloud here, but could you duplicate your displaced object in two versions to do two things.

Turn off generate GI on the displaced version, but leave in a non-displaced version to generate GI - in the System/Object Settings box make it a Matte Object with a Alpha of -1.0.

The test scene I made works like this. - basically a grey sphere resting on a patch of grass lit by GI. (can email it to anyone who wants) I made the different objects different colours so colour bleed would show up what the GI solution was taking into account, just to make sure.

Displaced grass excluded from GI generate and receive = 6 secs
Displaced grass excluded from GI generate = 57 secs
Displaced grass GI generating and receiving = 66 secs

Obvously with the 6 seconds version the Grass is black, but could be lit independently with either self illumination, or a light(s) including only the grass.

Is it a PITA? Yes - but it meets your requirements of one render pass. I agree that a checkbox "ignore displacement for GI" would makes things much easier, and is a great feature request.

I use this technigue to place invisible "fill cards" and "cutters" in some scenes, to control light distribution. Yes I was a photographer once - this method is very instinctive to me.