Ambient Occlusion artifacts

Neongoat

Hullo Polycount members, I'm afraid I need your help.

I'm a game art student from the Uk currently engaged in 'technical research' for my project and I seem to have hit a bit of a block. I've been seeing some awesome 'clay' renders around and thought I'd have a go at learning how to do them along with baking the light information to a texture. The tutorial i followed can be found here http://www.game-artist.net/forums/spotlight-articles/1317-tutorial-ambient-occlusion-maya-alchemist101.html.

Right, I'm just going to chuck this image up and hopefully it'll show the problems I'm having. Apologies if it's a bit large. Oh, I'm using Maya 8.5, if that helps.



The lines around the 'hip' could be down to the UVs I suppose, as for the line across the top of the mouth I have no idea, it's just a normal face :shifty:.

Feels like I've been wrestling with Maya for practially the whole weekend so any help at all would be greatly appreciated!

Cheers,

ng

MoP

Maybe try Unlock Normals and see if that changes how your mesh looks in the viewport. Sometimes normals can get "locked" after doing certain commands (like Combine, Separate etc) and while they look ok in the viewport they're actually treated differently when rendering or exporting.

Make sure you don't have any double faces or dodgy geometry (2 verts on top of each other), you should be able to check this with Mesh -> Cleanup.

Neongoat

Hi MoP, thanks for replying so fast. I had a go at your suggestions; nothing doing sadly. Could it be a problem with the geo? I have got some nasty ngons in there. Having said that, I tried rendering using just a lambert and mental ray and it looks fine, maybe something to do with the surface shader?

MoP

Yeah, I also thought that maybe the geometry is just too simple there for the AO to work correctly, although I really wouldn't expect to see the sort of triangle lines you have down the front of some faces though, that implies that something else is wrong.

Are all of the UVs which are mirrored, moved outside the 0-1 range? I noticed in your UV layout that you have moved several parts off by +1 U unit, which is good, but is that all the pieces? Could be that you still have some "stacked" UVs which might cause problems.

Neongoat

Mm, I went back into Silo and did an auto-layout of the UVs so they're all seperate, didnt make a difference at all. Short of completely re-hauling the UVs I'm clear out of ideas.

rebb

Are all the Vertices merged in these areas ?
Guess they must be judging from the viewport-shot.

butt_sahib

mind posting a wireframe over the model?

EDIT:
do you maya users have something along the lines of Reset Xform? Maybe delete history or optimise scene?

Neongoat

Rebb, Butt_sahib - Thanks for replying guys. I went and merged the vertices around the areas just in case, I think they were ok before, and here's a wireframe shot:

butt_sahib

Would you mind going in and baking out any other map. Like a lighting map or a color map?

Neongoat

Right, here we are, one shoddy light map:



The right leg (our right) has a funny seam due to it's UVs being offset, other than that it looks fine. Weird huh?

butt_sahib

Well the lighting map came out right. So that implies that theres something up with the Ambient Occlusion baking options?Did u use the same ones as ben did in the tutorial? dreadfully sorry, but im a hardcore max user
other than that....worrrrd

Joao Sapiro

use xnormal simple amboc tool, generates awesome amboc in 1 second or less, all you have to do is load the lowpoly in the high and lowpoly slot and use in tools the simple AO generator. You wont be sorry

funshark

Please check angle of the faces around the edges where you encounter the problem and UVs overlapping.

UVs overlapping always generate inaccurate baking and maybe the parameters for ambient occlusion turns to hard all the edges which are above a specific angle.

Warbringerd

One option I use when I get some weird artifacting form my Occ maps is to use the heal brush in Photoshop to smooth them out or just do an edit to take them right out if necessary.

Just my 2c's