View Full Version : Solid Colors & Ambient Occlusion

01 January 2012, 10:56 PM
I have two fairly simple questions that have been nagging me for a while. In Autodesk Maya, this is what my render looks like right now:

Then I want to add an ambient occlusion for simple shadows, by rendering out this:

My questions are, how do I render out solid colors for the logo (without shadows) and, as far as the ambient occlusion is concerned, how do I make the logo white (like the floor)?

I have tried adding the same lambert shader that I have on the floor to the logo, but the logo still comes out gray in the ambient occlusion. And the reason why I want the best color possible is because I am using the ambient occlusion for shadows and I do not want to muddy up the colors anymore than they already are. Thank you, in advance!

01 January 2012, 03:17 PM
You can add a lambert with the diffuse and ambient set to white to the letters, and only add the ao shader to the floor.


01 January 2012, 03:39 PM
If I'm understanding correctly it seems what you want to use is a surface shader as your material. There's no shading or shadows taken into account with surface shaders.

For the solid colors just apply the surface shader and set the out color to the color you want.

For the ambient occlusion you can again just use a simple surface shader apply the ambient occlusion as the out color.

Then to composite the 2 just multiply the colors by the ambient occlusion pass.

01 January 2012, 12:10 AM
@MikeBracken: Thank you, but I want to have the shadows on the letters as well, just not on the front of the letters.

@kanooshka: Okay, I applied a surface shader to everything and it did exactly what I wanted it to do. See here:

But I cannot seem to apply anything to the letters to turn them white after I apply the ambient occlusion. This is my current render:

It still has that awful gray tone on the front of the letters. And you can see in the composite how that gray is muddying up the colors. Sigh.

01 January 2012, 05:30 PM
You could always adjust the levels of the letters in post to get what you want? Since your color layer is just flat shading.

01 January 2012, 11:45 PM
What is the search distance of the ao shader ?


01 January 2012, 03:09 AM
@zmuh11: Now that you suggest it, that would probably be the best way to go. Now, I have to figure out how to do that in Adobe After Effects.

@MikeBracken: I looked through all the attributes of the ambient occlusion and I could not find "search distance." But from what it sounds like, wouldn't limiting the search distance make it so only the shadows in the front will appear? Because I would actually like to keep the shadows that are all around the letters, including the shadows on the inside curves of the letters. I just do not want my letters to be gray.

01 January 2012, 03:44 AM
Could you post your settings for the ao texture?

01 January 2012, 04:23 AM
@kanooshka: Sure thing. Here you go...

Samples: 16
Bright: White
Dark: Black
Spread: 0.800
Max Distance: 0.000
Reflective: Unchecked
Output Mode: 0
Occlusion In Alpha: Unchecked
Falloff: 1.000
Id Inclexcl: 0
Id Nonself: 0

...and that would be it!

01 January 2012, 05:15 AM
I think your issue is with the scene scale and max distance. When you leave the max distance at 0, Mental Ray will decide on the best distance at render time and sometimes that doesn't work out very well.Start with a max distance of 1. If it's too white increase the max distance. If it's still too dark, decrease it.


01 January 2012, 07:13 AM
@kanooshka: Well, that seems to have done it. It minimizes the shadows that the letters are casting, but not by too much, and the letters are now white. I believe in the render below this, I used a "Max Distance" of 1.500.

01 January 2012, 05:17 PM
If that's still not what you want. This link might help, it explains how to include/exclude objects from occlusion.

01 January 2012, 12:08 AM
@kanooshka: Thank you. That looks like it should be right up my alley. I will read it later tonight. Thank you once again for all of your help!

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