A Question about Vray 1.5

[lordshaitan]

Ok i got to thinking, since Vray handles specular the way real life does, how will the reflection and specular pass work?

In the specular pass will there only be objects that emit light? And in the reflection would be everything else that is reflected?

But what would happen when say a light is shiniing on a box, and the box thus emits reflective light in a GI situation, what happens then and what pass will it be in?

Thanks
Jeff

[egz]

You will get "fake" speculars from normal light sources. These show up in the specular channel. VRay lights and bright objects will show up in the reflection channel.

[lordshaitan]

Is there a way for at least Vray lights to show in the specular? Without having to actually manually go in a change the scene?

It would be nice to have the freedom in post to have a reflection pass separate then the specular, and not just "fake" specular. Say anything in reflection with a GI bounces level greater then 50 (from a scale of 1-100).

Also, it would be nice to have this freedom from and HRD reflection too.

[cpnichols]

Well Vray lights are area lights so their "specular" is hard to use in the normal way (pun intended), they can only really be seen in a reflection which is a real specular. If you want a traditional CG specular highlight, you may want to make a "specular only" light right on top of the vray light, and make the vray light not visible to reflections. But now that I say that, it does sounds bit complicated. It would be nice to have more flexible (although not correct) options for the artists.

[lordshaitan]

Well if it was correct, anything emiting light would make a specular correct?

Granted i know that in this scenes w/ reflections and alot of light sources the reflection and specular passes would start to blend, but in a profesional situation i would like this, because i can control them easier in post.

Personalyl i dont think its alot to ask for, but programming wise i do think it may be a problem.

[egz]

Well if it was correct, anything emiting light would make a specular correct?

Not really, they would make a reflection. Speculars are simplified reflections that don't exist in the real world.

Granted i know that in this scenes w/ reflections and alot of light sources the reflection and specular passes would start to blend, but in a profesional situation i would like this, because i can control them easier in post.

Personalyl i dont think its alot to ask for, but programming wise i do think it may be a problem.

You'll be happy to know that I just did a test, and I was wrong earlier: a VRay light does actually create both a specular channel and a reflection channel.

[lordshaitan]

Nice! Thanks for testing it, I appreciate it.

[vlado]

The actual phenomenon is only one: reflection; however, there are two major strategies for computing this. One way traces reflection rays from the surface, the other way traces light rays from the light (this is very similar to the way GI solutions work, but this is at a local level for direct light). The first method is typically referred to as "reflection", while the second method is referred to as "hilights". It is important to realise that they compute the same thing.

In some cases (shiny surfaces or large lights) the first method performs better; in other cases (glossy surfaces or small lights) the second works better. It is possible to combine the two methods, where each will compute only the part which it can sample best. This is what VRay 1.5 does. So, area lights generate both a "reflection" and a "hilight". When added together, those produce the correct result of the light reflecting on the surface. However, for compositing purposes, they are separated and can be controlled independently.

Best regards,
Vlado

[cpnichols]

When added together, those produce the correct result of the light reflecting on the surface. However, for compositing purposes, they are separated and can be controlled independently.

ooooooh... that sounds SO sexy!

[TRGraphics]

I agree, it sounds like vray is going to be "the renderer" to beat! What a package.

Tony

[lordshaitan]

Now if only you can account for surfaces that have recieved a strong amount of light and therefore are actually emiting bounce light and have that in a seperate pass and were all good to go

[J_Bug]

Great logic Vlado Thanks

--Jon