Ambient Occlusion problems

[Kai Hopermann]

Hey guys,

I ran into a problem using AO. Everytime a black shaded object is placed in front of white shaded objects, a white rim appears where it should not be!? Even between the white and the black shaded object although it should occlude black.

Take a look at the images, maybe its better to understand because a picture is worth a thousand words.

I´m using max2010 and vray 1.5 SP4.

AO pass


diffuse pass


comped


closeup


Here are my rendersettings and AO settings in the material editor


Someone knows why this happens or how to solve it?

[dlparisi]

Looks like maybe your white in the diffuse pass is past 1 which means it's not anti-aliasing correctly and it's "bleeding" over into the black area. When you multiply the diffuse you that bleeded area is not getting any dirt applied to it.You can clamp the values and see how that works.

[Kai Hopermann]

Hi dlparisi, thanks for your comment.

Here´s the clamped output to 0.9.
Did you mean render settings>Vray colour mapping>clamp output ?



and another one without reflections

[dlparisi]

Sorry, forgot to mention you also need to check sub-pixel mapping for AA to be correct. Did you have that on too?

BTW- you can probably leave it clamped to 1 (not .9)

[Kai Hopermann]

... no I didn´t check suppixelmapping but even though I checked it... the same effect.
I put clamped output back to 1.0

[dlparisi]

How are you comping the AO pass?

[Kai Hopermann]

I tried it with Fusion 5.3 and Photoshop cs2. I merged the AO pass via multiply over the diffuse pass. Am I doing something wrong?
I did it multiple times with other jobs an there where no problem. Only in this special case, if a black Object stands in front of a white object.

mmmhhhh....

[dlparisi]

By chance is the white line just the reflection of the white cylinder on the curved black edge? The black piece looks like it has rounded edges.

[Kai Hopermann]

yes there are rounded edges, but I tried to render it without reflections. I unchecked it in the vray rendersettings and nothing changed. Really strange. I give it a try without rounded edges but I´m with your first suggestion that something is wrong with the AA settings... and thank you for your help.

[Morbid Angel]

its strange but diffuse pass looks to have reflection in it, so its not really a true diffuse only pass.

[Kai Hopermann]

Hi Morbid Angel;

yes thats true but I already tried it without reflections and it was the same problem. But thank´s for help.