CGTalk - How To Make Render PASSES

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le_faya

01-17-2006, 10:41 AM

Hi All,

I am currently trying to make a render with passes (with MENTAL RAY) and i would like to know if i make it wrong:

I render
_Diffus passe (i make a render with lighting+light in ambiant only+without shadows)
_Ambiant Occlusion
_Shadows (i put a white materials to all objetx and i render with shadows_i make this because this is the only way i find to get the shadows on the objets and the shadows of the objet on the environement)
_speculare passes (black materail with a specific speculare value for each kind of materials)

But when i Mix all this i don't have the same image that the original with GI, and my image is to much dark.

I could post example if u need more, But if someone get a good tutorial or advise to make render with different passe with Mental Ray; i will be happy to see it :)

THX

jeremybirn

01-17-2006, 03:03 PM

_Diffus passe (i make a render with lighting+light in ambiant only+without shadows)

That sounds like an ambient pass, not a diffuse pass. A diffuse pass has the diffuse shading from lights, not ambient light. (You didn't say which software you are using. I've heard that in 3D Studio Max, when rendering a diffuse pass, there's a Diffuse Texture Element Lighting checkbox that should be checked for a diffuse pass, unchecked to make an ambient pass. Maybe that's why some people switch the words diffuse pass and ambient pass?)

But, for your regular lights, you need (diffuse+specular)*(1-shadows) to make your scene look like a regular render.

It's also good to render an ambient pass, and an ambient occlusion pass, and multiply them together to create a nice extra fill light. You can add this to the composite above.

-jeremy

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