How is Raw Light pass calculated?

[drew_almighty]

I am having some strange issue with the raw light pass.

What seems to be happening is that the shader used on the geometry is affecting the raw light pass, but it would seem to me that the raw light pass should be disregarding the shader completely.

 

Does anyone know what exactly is happening in that pass? Do any values from the shader affect the raw lighting pass?

[Stephen Thomas]

Diffuse colour/texture won't be included, but obviously reflection/refraction values will have an effect on the diffuse component that can receive light.

 

In other words it doesn't disregard the shader entirely.

[drew_almighty]

I guess it's the "obviously" part I am looking for more information on. So more reflection = less raw light because the rays are being reflected?

All things being equal how does reflection glossiness then affect raw light?

[Francisco Penaloza]

From what I understand, while V-Ray does its magic, still consider some color, reflection, refraction and other properties of the material to calculate GI. So even tho you have a RAW pass, you still need to use a filter pass to control or adjust that pass.

 

Depending of the app you are using to composite your passes you also will have to use a combination of other passes to get a RAW pass.

For instance in NUKE you are better using a Gi pass divided by the diffuse pass to get a RAW GI pass.

I don't know more in depth explanation because for what I do regular passes are more than enough but if you need the exact definition and explanation of all this passes I would recommend to post the same question at Chaos group forum, there V-Ray team will give you developer level answers

Edited October 25, 2016 by fco3d

[Nic H]

why do you need the raw light pass?

[Stephen Thomas]

I guess it's the "obviously" part I am looking for more information on. So more reflection = less raw light because the rays are being reflected?

All things being equal how does reflection glossiness then affect raw light?

 

Reflection glossiness shouldn't affect it. To elaborate a little, Lighting and GI are only visible on an object when they are illuminating the diffuse component. Shining a light on a fully reflective or fully refractive object, there is no diffuse component so you wouldn't expect to see this object show up in a lighting pass. Where an object is partially reflective or partially refractive, you would see partial illumination in the lighting passes.

[drew_almighty]

Thank you. That's what I was looking for.

So while the color of the diffuse doesn't matter (as long as it's not completely black), the amount of diffuse contribution affects the raw light.