Ambient Occlusion - Missing Parts

Acumen

ok, simple question, i hope simple solution.
so i'm working on a simple tf2 pillar pack (lots of different variations - model and texturewise) and rendering out a colored ambient occlusion texture. so sometimes all the bolts are visibly casting shadows and sometimes now. i got 4 variations so far. i started with one base mesh and just copied and pasted the model parts with increasing height of the pillar, reorganized the uv's and then baked the texture. and like i said, sometimes it works, sometimes not. since i haven't saved one superior render scene file, i always have to make my rendering options for the light tracer again and again for each model variation.
so i'm assuming that i might just have missed an option. because i also had the situation that i checked and unchecked variables here and there on my third pillar model and then somehow the bolts were visible (i just FORGOT how ;()
when i move the floating bolt parts out of the mesh the shadows are rendered - but of course that's not the same

Anyone know what i've done wrong or what option i'm missing out on ?

here's the pic anyways - the circles show where the bolts are not properly showing up:

boyluya

I don't if this is right but maybe you can check the normals of the bolts from your high poly version, it may be reversed. Hope it helps.

Acumen

oh
there's not a single high polygon involved in this project ^^

Mark Dygert

1) What app?

2) Still check that the normals are facing the right way.

Turn on backface culling and flip anything that is inverted. Max and Maya both default to not culling backfaces as it saves performance. So something could be facing the wrong way and you'll never know it because it displays both sides of the poly.

If you're a 3dsmax user you might want to avoid using the mirror tool as it flips meshes inside out and isn't apparent until you reset Xform. Instead use symetry it doesn't negatively scale your object.

boyluya

Acumen wrote: »

oh
there's not a single high polygon involved in this project ^^

Oh sorry, I didn't read the whole thing. I just based my answer on the image..
Yeah, just like Vig said, check the normals. I think it must have something to do with the normals.

Acumen

sry, it's 3ds max.
what i did was, just copying the bolts upwards via shift-dragging. the bolt is a 6-sided cylinder of which i deleted the bottom - where it intersects with the geometry.
so since i started with a single bolt and just shift-dragged and then rotated it, i don't really know, what could have gone wrong here

LEViATHAN

Is it that big of a problem anyway? You could easily stamp the rendered shadows over the missing ones. :shifty:

NoisyMonk

This would be strange, but its possible that one of these mayb have got turned off by mistake; 'renderable', 'visible to camera', 'cast shadows', etc..

Mechadus

If its only small details that go missing, it could very well be your anti-aliasing settings as well. Sometimes if your AA isnt properly set up, it will render over small details. If your using MR, try using the Mitchell filter with 4,16 AA (assuming something else isnt the cause of your problem anyway).

-N!

Mark Dygert

There are a few other ways to get inverted pieces, you could have flipped the piece inside the UV editor also.
In the editor window go: Main Menu > Select > Select Inverted. Flip anything that it highlights. But I'm not sure if that would trigger missing AO...

Also make sure to move any pieces that overlap 1 unit over.

If that all checks out, select the object, go to the utilities tab (hammer) and click reset Xform, then click reset selected.Then right click, go to object properties. Check on Backface Cull, flip anything that is inverted.

Instead of using Mental Ray, why not render a diffuse map with a lighting/shadows turned on with either a skylight or a light dome. E-Light dome is pretty handy for that kind of thing and renders faster than MR-AO and Skylight.

If all that doesn't work I say forget it, and copy/clone the shadows in photoshop and move on.

Acumen

1) i had no inverted or overlapping pieces, when checked
2) i think the anti-aliasing might be a guess

sure i could stamp it, but i kinda wanted to understand the problem. since some shadows are crips and sharp. others are kind of meh, and the rest is totally gone. just from one single cylinder copied around.

so i did another test:
i just deleted all of the bolts except for one. then i copied this around again. and now everything gets rendered except of one bolt.
it's just. i don't get it why
i'm using skylight (light tracer).

thanks for your superfast help so far, you guys !

Ghostscape

It looks like one of the bolts rendered only half of it.

Could you post the scene maybe?

is it all merged as one object?

Acumen

yes, it's one editable poly
the scene (max 2009) without the skylight:
www.acumen-design.de/temp/ao_test.max

edit: after lots and lots of trial and error, i came to my personal conclusion, that it's totally random and i can't even reproduce it with following the same steps..
one time all of the bolts were visible. then after not having changed anything, two bolts were missing again. it's annoying
/me clones and stamps !

mLichy

Interesting....

On a side note, did you offset any of those endcaps for bolts or whatever they are? You could do that if you already haven't and make some UV space, and scale up some other pieces to utilize more 0,1 space.

Acumen

so, um, i just could not resist and do some more tests, and after mLichy wrote something about scaling, i thought, why not scale the render output size, so i made a 1024x2048 render and badabam, there you go, all elements visible.
weird weird weird - at least for me