VRay Rectangular Lights- A Few Queries

[thomthom]

Re: VRay Rectangular Lights- A Few Queries

That's very interesting.
And Vlado is a V-Ray, developer I take it? I've not used the Chaosgroup forum's so I'm not familiar with the people there.

[dalomar_cg]

Re: VRay Rectangular Lights- A Few Queries

What I REALLY don't get is the general concept of skylight portals forcing VRay to look for light sources

In order to determine the intensity and color of the light behind it, a light in skylight portal mode must do some ray tracing from the back of the light out to the scene. As with sampling from a given point in the scene, and light source that will be visible to that point on the back of the light is automatically traced in addition to standard GI sampling. In this case, the standard GI sampling is what's catching the intensity from the emitter.

just placing skylight portals in the vicinity of an emitter source seems bizarre.

If this still sounds bizarre after reading through my post above, then let me know...it really isn't though.

It's seem like VRay is having to make some kind of volumetric/spatial calculation between portal and emitter just to work out if the portal should have any effect on the result.

Remember, V-Ray doesn't know that there's anything behind it, so it has to find out. It does so by a process of taking a hemisphere and sampling different points within it to find out the amount of light and the color that's going on behind it.

I mean how close should the portal be to the emitter,

In the case of trying to sample emitters probably as close as you can get so that A)the emitter gets sampled well, and B) the light looks like its coming from the same direction

how many should there be, etc, etc. How does one calculate how many portals, what size they should be and how close they should be to surround a cylindrical or organic formed emitter source?

As few as possible to get decent coverage around the emitter. You don't really wan't to be throwing an extra 20 rec lights in your scene just to get a good sampling of an emitter. Remember to the discussion that was had a while back about controlling the subdivisions in situations where there are a good number of lights.

That's very interesting. And Vlado is a V-Ray, developer I take it?

Its called V-Ray for a reason* Vlado is the man behind almost everything in V- Ray


*It is only speculated that the V in V-Ray is for Vlado. Vlado has not said that his own name is the basis for it, but you've got to admit that its a striking occurance

[thomthom]

Re: VRay Rectangular Lights- A Few Queries

I was asked not too long ago, by one of my co-workers, what V-Ray stood for. And my reply was; "Errrh...".