AO Maps and Hovering Polygons

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  02 February 2013
AO Maps and Hovering Polygons

Hey all,

On my latest project, I have these round access discs (removeable disc panels for gaining access into airframe structures). I created them in 3D, and I attach them to their parent structures for precision mapping and ease of repainting for enthusiasts that download them later.

But, when I burn an AO map with these discs on them, the map render sets them as black. But if I were to hide the Elements of the Discs and burn them, then the map would show nothing there, (no shading) which I need/want.

Is there a miraculous work around for this?

Attached Images
File Type: jpg AccessPlates.JPG (90.9 KB, 45 views)
  02 February 2013
Chances are your normals are inside out. Just select those objects and put a normal modifier on them, should do the trick.
  02 February 2013
It looks like that is CAD data, which is notorious for not caring about normal direction. To be able to see flipped normals easily in the viewport Disable Backface Cull on Objects (or Layer if set to display by layer), set Viewport Configuration > Visual Style & Appearance > Lighting and Shadows > 1 Light, set Display > Shaded > Object Color. Now anything with flipped normals will show as Black and those with proper normals will show as object color.

"The Evil Monkey hiding in your closet."
  02 February 2013
Well, the discs appear to all be facing the correct directions. Normals are normal.

I was trying to figure a way out to just push this through the Ambient Occlusion last night. Perhaps I could do an AO on just the discs (hide all Elements but the Discs) and save that, then save that as a layer in Photoshop 'over' the wing and then I should have lower shading without the black dot on the top of the discs.

I think whats happening is that the wing surface is lastly rendered instead of the discs, even though the discs are part of the object. If only I could reverse the render order, but then that would probably make the shadow disappear.

  02 February 2013

An alternative might be to use a self illuminated material then with AO in the diffuse slot and try that... has been known to work for me in the past.

Otherwise I'm stumped, unless maybe the AO distance is just too high and it's pooling up all over it. However I'd expect to see a gradient then not just pitch black.

I wonder if you could post up a zip with just one or two of those rings for testing.
  02 February 2013
Hey BitVoxel,

Here is the wing. Your welcome to check it out.

I see that this has happened on the fuselage as well, in a couple of regions like an exhaust cavity in the cowling and on a window that has a layerd up ridge surround that is over the fuselage surface. Those area's are black also.

Attached Files
File Type: zip (221.7 KB, 3 views)
  02 February 2013
Well, this pretty much makes sense that it will not work. I attached things on top of surfaces and Max doesnt know one from the other in levels of priority, or rather perhaps it just makes one single map render for all sub-objects, which as I said, makes sense.

What I ended up doing is detaching the subobjects (on the wing, the little discs, and on the fuselage, the rear window raised bezel rims), then hiding them, re-rendering the AO maps, then used the previous AO maps to make outlines of the sub-object shapes, make a layer with those lines, blurred them, then they became a home made AO layer for those sub-objects....


It does look good. The rest of the AO rendering is brilliant.
  02 February 2013
I apologize I didn't see the previous post. I'll play with it asap.
  02 February 2013
Hey AJ,

No worries Man.

If you can make it work, I would be massively interested how its done, but I kind of feel it might not work. Its like shading a layer that is in a stack of sub-object parts that are all 'attached'. I dont think Max knows which one to make the top. It thinks 2D, I think.
  02 February 2013
Yeah I spent some time on it last night but made no progress. I've haven't seen this problem before. Now it's sort of a pride thing so I'll keep at it but .... weird. Thanks for being a sport about it.
  02 February 2013
No worries man. Thanks for checking it for me.

So... Normally these 'will' work properly in Max? If so, then I shouldnt be dealing with this again, as I made that originally in Gmax, then purchased Max, and migrated the model into Max and continued on. So this could be a Gmax to Max issue, older mesh.
  02 February 2013
I think I solved this one. The uvs are overlapping in the unwrap window so the AO bake is getting confused. When I took the circular shells outside of the wing mapping to an empty spot the problem went away.

Should have spotted it sooner, but hey at least it works!

  03 March 2013
Roger that.

Thanks AJ. Most appreciated.
  03 March 2013
Happy to help! I don't get to use max much anymore so it's nice to get back into it. Thanks for being patient!

Have a great weekend,
  03 March 2013
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