View Full Version : ambient occlusion when rendering one object?

07-21-2005, 03:20 PM
Hi all,
I'm afraid I might be making a fool of myself but the sage says one learns making mistakes ain't it? If any shader wise soul wouldn't mind taking a look at the following images I'd be appy.
I modelled this sculpture in Maya 4.5 and applied a layered shader to it:
image1: http://www.digizetta.net/html/gallery/progress.htm (http://www.digizetta.net/html/gallery/progress.htm)

Then I thought it might look better with ambient occlusion. In maya 6.5 I added the mental ray Ambient occl shader in the layered shader (first layer) and after a few trials and putting lights intensities 5 times higher I got the second image2.

There's not really much difference...

So , 2 possibilities:
1) I didn't configure the ambient occlusion shader correctly.
2) This is going nowhere as ambient occlusion only works with 2 or more different objects touch themselves...and I just have 1 object here.

or what?
Thanks anyway for reading.

07-22-2005, 06:05 AM
Hei man

Also Suggest you using mix8layer shader from Francesca instead of Layered shader....i dont know if Layered shader works properly with MR....

I m posting my the 6.5 setup of Ambient occlusion...
I got interested in your question about whether AO works if you have just 1 obj in the scene...

So it looks like it does.....:thumbsup:
Take a look

07-22-2005, 11:31 AM
I should have tried that myself of course...
I'll explore further with the mix8layer shader.

07-27-2005, 10:51 PM
What does your ao pass look like? It looks like its working normally to me.

The AO shader in 6.5 works fine on 1 object alone, by the way.

07-28-2005, 10:48 AM
You're right daddyo, it does work normally:


It seems I thought I'd get more spectacular results with the ambient occlusion. I'll try some tweaking and compositing. The 2 first color renders are not composited, they're just flat direct renders.

08-04-2005, 11:03 AM
Well i ve got some questions about AO pass...Hope you guys know the answer

Its ok when I render an object in exterior with Surface Shader`s out color mapped with dirtmap or mib_amb_occlusion.......we get clean AO pass without a problem

But when I do the same for the interior scene i cant get proper pass because all sample rays are blocked by my interior walls....There is a workaround when i hide the ceiling but then its not get rendered and doesnt take part in AO pass what is not what i wanna do....

My question is....is there are any way to hide some geometry ( in order to let sample rays reach the rest of scene ) but still to be able to use it for AO calculation...

I tried using Transmat material but that didnt work ...:banghead:

Thanx in advance

08-04-2005, 01:25 PM
Hey Leha,
Wouldn't it be a solution to make (or duplicate) another lightset for Interior scene, linking lights to objects accordingly...?
Or tell ceilingShape not to cast shadows...? =

just suggestions...

08-04-2005, 01:47 PM
Thanx for the quick reply man ..

Of course i tried Cast Shadow flag before posting the previous post....didnt work though....
On your pictures do you use Surface Shader ot Lambert ? ( Lambert i guess , ha ? )
Do you have any lights in the scene...

I guess the problem is that i use Surface Shader instead of LAmbert ( for faster rendering, you dont need any lights then )....Surface Shader as i know actually doesnt care about Lights at all......and as a result Cast Shadow flag doesnt work here.....

I also tried to mess around with Mental Ray setting in the transform node but again no avail...

Anyway if i wont find out what to do i ll go the LAmbert way...

Thanx again man

08-05-2005, 11:41 AM
Lambert it is with 2 dir lights (1 key , 1 fill) and 1 ambient inside box.
I never used surface Shader...

08-05-2005, 11:51 AM
Thanx for the input bro...

Anyway i ve found the answer this morning in MAYA Rendering Forum section..

You can control the distanse of AO with Max distanse setting and the spread with Spread attr....

Works like a dream :bounce:

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