AO + transparency + MR

adam

I'm preparing to render out some AO magic and can't find out where, or if its possible, to render transparency masks with the AO or if it can only render the mesh itself. The scene (DW2 stage) has a lot of vegetation which means alphas on planes, I'd like to render the AO with it omitting the transparent areas.

Anyone have any insight on this? Thanks!

adam

It looks as though the issue is with MR only accounting for the mesh when it renders AO and not the materials what-so-ever. Checking online someone suggested to another who had the same issue as I do now that they look for an alternative AO shader that'll allow you to feed it materials.

I'm still open to ideas, however.

Anyone have a seperate app they use for rendering AO that'll account for materials and mesh?

Thanks!

Rick Stirling

I had issues with this in the past - AO and normal maps and transparency.

I ended up building a spotlight based lightdome instead of using a skylight.

SkullboX

It's not really a mental ray issue it's simply the way AO works.

Is this for rendering or texture baking? I have solved some alpha related problems with ambient occlusion (though you will never get each straw emitting shadow individually) but only for 'regular' renders.

If you post an image of what exactly you're trying to get to look good that might help a lot.

CodeFather

If it is for baking with RTT , Max9 has got a nice exclude option in the Ambient Occlusion(MR) element...in prior max versions one way to exclude objects is to assign them a specific G-buffer ID, than in the AO shader there is an option to include/exclude objects by this ID(To exclude objects enter the ID nubmer with a minus(-) sign infront of it). Assign the AO material to the target objects and finally with the help of RTT ,render out a diffuse element with shadows only turned on...

adam

Skull, it'd be for renders not texture baking.

It was for this here:
http://www.adambromell.com/models/images/domwar2_stage02.jpg

Code - thanks! I use Max7 still though...

onehundredfeet

That's a common complaint with the MR AO computations. I built a renderer/baker for our game which handles the translucency issue with regards to AO and shadows. It's built into a Maya plug-in with no Max support atm.

Backboard

You can see the translucency in the back-board and the fence shadows. It works for ambient occlusion as well, and all levels of translucency (not just on/off).

Same with the tree shadows:
Trees

adam

You work with Malcolm I presume? I'd like something like this for Max... very jealous :P

onehundredfeet

Yeah, we worked together on the project above. I used to use Max, once upon a time, and maybe if they force me to use it on Need For Speed, then I'll port it.

Sage

Adam try telling your lights to render raytraced shadows and see if that works, since they seem to take alpha channels into account. You may have to layer them in photoshop to get the look you want.

Alex

FatAssasin

Have you tried to just render the AO pass without worrying about the transparency? The shadows you'll get are so soft, it probably won't make much difference whether it's taking the alpha channel into account or not.

Ryno

Skylight, cast shadows on, up the samples, no advanced lighting. This will do AO and will take opacity into account, but it's friggin' slow.