Mental Ray AO is all black.

Cody

*edit* I bumped this thread because of similar problems- new post below

Hey guys. When I am baking out my Ao, the final image everything is all black. I'm doing it the right way, I am 99% positive. Usually when I render it out, there is a window showing me the render, and I just save from that, but now that window is gone, and just the bar showing me progress is there. So the two questions,

1. Why would my Ao turn out black [it has the silohette of my unwrap, just it is all black]?

2. How do I get the render window to show?

Mark Dygert

More then likely the UV pieces need to be flipped. If you're using 3dsmax go into the UVEditor window, select face mode, click Select > Select Inverted Faces. Flip anything it highlights.

If you used the mirror tool it inverts your UV's and they always need to be flipped.

Cody

Okay, just checked that and I didn't use the mirror tool, and none of the faces needed to be flipped. Thanks though. Any other ideas?

Eric Chadwick

On the low-poly object, go into Face sub-object, select all, Hide Selected Faces. Then try again.

solar

If you're baking from High to low poly model you'll need to go into face selection in the low poly model and hide the faces (not the same as hiding the object).

-Edit- too slow!

Cody

Boom. Thanks Eric and solar. Ao is looking tasty. Look at that. Posted a problem, and it's fixed in a hour. Polycount ftw.

Eric Chadwick

Next time try a search and it'll be even faster.

Cody

Hey. Bumping this thread because it's happening again, and the answers in this thread aren't fixing it this time. the faces in the low face sub obj are hidden, no uv faces are overlapping or inverted, all the settings to my knowledge are correct....so im at a loss here. cage is good, high geometry is selceted, mental ray enabled.....no idea what the hell it is now. tried google searches and looking here, no luck. ideas?

Mark Dygert

You need to select the low, go down to the element mode and hide them using the hide option in Edit Poly and then bake. More then likely your high poly isn't unwrapped (at least not in a legible way) so its coming out black.

unless you meant high geometry is selected as the projection model, in that case it could be anyone's guess because it sounds like you're doing things right.

Cody

Ya, the high geo is set as the projection/reference. The low is unwrapped all good, and is hidden [tried hiding it in faces and element]. so ya wtf?!?

Sage

make sure you have the ao in the right channel. I think you it's called ao refractive map or something... maybe it's reflective. At any rate if it's on the wrong channel it gives you black. the other thing that screws it up is lights. If you made a light turn it off. That's the only thing that comes to mind. Check that the cage or ray distance is set correctly for your model...

Cody

the target map slot is ambient color. thats what has worked for me before.... there are no lights in the scene. cage is good, ray distance good. i just rendered a top down view and lined it up with my normal map, and hand painted in some...it worked well for this model. but if anyone else comes up with ideas feel free.

Mark Dygert

err if you're using render to texture and the output map is set to AO you don't need the MR AO material in a slot.

You can try the old "create a box, convert it to Edit Poly and attach your low poly mesh then try to rebake.

Cody

hmm will try it tomorrow, thanks vig

mikezoo

Food for thought. Max bakes out Ao really, really well. But I personally think xnormal can bake out a better job. Render time does take longer.

Personal taste though.

Cody

hmm...might bite on that thought sandwich, mikezoo....

mikezoo

Really, xNormal is great, simple to use, and free!

Sage

This is how I have done it in the past. Assign mental ray as a renderer. Assign ambient /reflective occlusion to the reflection slot. launch RTT, make a light turn it off so the scene turns black and bake with RTT. That's the only way I gotten AO with MR to show up as an option in RTT. The other method has been to use the skylight and scanline to render it using the light tracer. The other option I have used is set up a white material and light the model myself.

Vig how to you get the ao bake option in RTT to appear without having to assign the material to the slot?

Mark Dygert

As long as your render engine is set to Mental Ray it shows up in RTT.

The MR-AO material does a few cool things the most common is for beauty renders, you apply the material to everything and render out AO and multiply that over your first pass.