Ambient Occlusion pass

[Zac-Donald]

Most of the articles I'm finding about setting up AO passes are 3+ years old, is that still the best way to set it up (using a dirt-map) or is there a better way?

[Shine]

Well, you can just create a new pass and apply an ambient occlusion shader to the background objects partition. Render that out and your done. Roughly the same way dirtmap is done. Both solutions seem to work fine. Depends on the result your after as they differ somewhat.

[Zac-Donald]

What about doing AO with semi transparent objects and bump maps? whats the best way to do that?

[MmAaXx]

for semi transaprent obj and bump I think that you can resolve with a partition of the AO pass or (better) make another one with just the "special" obj

[bt3d]

The normal ambient occlusion shader of XSI doesn't take transparence into it's calculation. Take a look at the ray length shader of the BA shader collection for using AO together with transparent objects.

[NagyG]

What about doing AO with semi transparent objects and bump maps? whats the best way to do that?
http://www.xsibase.com/forum/index.php?board=12;action=display;threadid=34872

[Zac-Donald]

BTW how do you bake an ambient pass into a texture?

[MmAaXx]

there is the ultimapper for that

[GeneCrucean]

> Create an empty pass
> Hide both partitions (because everybody should be doing this!)
> Create two new partitions (one for lights and one for objects)
> Move desired objects to new partition
> Add an override to new object partition
> Add the surface port to the override
> In the surface port plug an AO shader into that and adjust it's settings.

If you do it this way it won't affect bump maps or displacements among other things.

[Splin]

> Create an empty pass
> Hide both partitions (because everybody should be doing this!)

Now, exactly why should I be doing this?

+How can one take into account lighting information in their AO pass? I saw a nice tip from kim long time ago about that topic but after hard disk accident I have lost that info. Since then I have not been able to figure out elegant way for doing this...

[GeneCrucean]

Ah I'm glad you asked...

http://www.genecrucean.com/tutorials/HiddenBkgPartitions/

[CiaranM]

Nice little video and a very useful tip. Thanks!

[Splin]

Allright, could have just said it with few words...
Still I consider it to be just a preference.

[GeneCrucean]

Hehe yeah, I actually wanted to test a new microphone I have. Sorry about that. Pictures do speak a thousand words however, and I do think noobs will understand why better with the video.

Everything you do in 3D is a preference. But I consider this good practice.