Ensuring uniformity of AO across modular assets

danshewan

Okay, so I've finally started optimizing and unwrapping the modular assets for my environment WIP, and I've been wondering about AO, and it's role in the texturing process.

Up to now, I've optimized a couple of structural elements to get 'em into UDK (right now, just a couple of wall sections, one straight and one corner, and a floor panel). I've thrown a very rough base diffuse on to them, which includes an AO pass rendered out of xNormal.

This has proved fine in Photoshop for giving me a better idea of the depth of a texture's surface and where certain details are recessed etc. However, upon importing the two elements into UDK (in this case, the straight and corner wall sections), the difference between the two sections is very obvious due to inclusion of the AO in the diffuse:





So, how exactly should I be handling the AO? Is it the wrong approach to multiply the AO pass over the diffuse? Or if not, how do I ensure uniformity across the different modular sections which have all been baked separately in xNormal? :poly136:

Obviously I'm really unfamiliar with this part of the process, and no doubt I'm doing something terribly wrong (and probably really obvious, stupid and deserving of much ridicule), so if someone could point out the error of my ways and maybe give me some pointers, I'd be pretty stoked if I can get back to work fixing it.

As always, thanks in advance.

Ark

Havent used Xnormal for baking, but in mental ray you can adjust the distance settings in the shader itself so you only get AO in the deepest occluded areas of the mesh.

In the mesh you posted, it looks like theres more ambient shading going on, then the AO effect because your distance is set to high. The only place i would expect to see AO in that mesh would be the corners and the insecting point on the floor/ceilings, not along the wall which you have now.

Parkar

Yea as Ark says your problem is that the on the corner piece one wall is shadowing the other. Lowering the trace distance should solve that.

Also when doing the AO on modular pices it is usually a good idea to add an instance on each side the module should "tile". You can see how you have a slightly brighter spot at the end of the trim on the flat wall piece (not as obvious due to the bigger problem though). This is because there is no wall shadowing it once you get to the edge of the wall.

Edit: In this case I would use the same texture for both the flat and the corner piece unless you plan to add more differences to the texture. the tiny bit of AO you get in the corner isn't worth it, especially in something like UE3 where you have Lightmass and SSAO.

jocose

Given how simple those objects are I think its the kind of thing that you would just do with a gradient Pshop, or like Parkar said, not at all, and just let the lightmaps handle it.

r_fletch_r

+1 to what ark said. Mentalray AO is a bit slow but it gives you a ton of control. Perhaps you can set the distance in xnormal.

danshewan

Thanks for the tips, guys.

Is UDK's SSAO a valid substitute for individual AO passes on assets like these simple wall sections? Or is it best used in addition to, rather than instead of?

Guess I've got some documentation to read...

Ark

I think on a simple wall like you have there, where there isn't that much surface detail, you aren't gonna get that much from a AO pass.

I think subtle AO baked into textures in combination with SSAO is the best route to take.

danshewan

Cool, thanks for the advice.

PixelMasher

for something like this i would use a common tiling texture with no AO really for the texture for each piece, there is no need for unique diffuse/normals for each piece given what you have there.

UDK's SSAO along with baked lighting will look a lot better too, plus then you wont get AO multiplied over top of the texture AO making things black and blotchy uglyness.

mortalhuman

This is kind of off topic and I promiseeee I am not trolling, but I have to say it: I really dislike UDK.

edit: had some constructive stuff here about baking AO, but it didn't really relate to the topic either so removed as to not change the direction, had to say something at least. soz.