RTT MR AO Issue

jeremiah_bigley

Settings:

Using Cage
Furthest
Ambient Occlusion Map
Using the built in AO Settings:
- 175 samples
- Spread: .75
- Max Distance: 40
- Falloff: 1 (default)
Final Gather off

I have already tried a Light Tracer AO and it works fine. I am more just curious if anyone knows how to fix the MR AO with this issue. I have rendered AOs through mental ray plenty of times before and this is something new.

It seems to be where the lowpoly and highpoly intersect. It is on the entire map.
Anyone have any ideas?

r_fletch_r

try unchecking renderable in the low polys object properties

jeremiah_bigley

Everything is on renderable. I just checked the backface cull and that was not it.

mbullister

I think that unchecking the renderable attribute prevents RTT from working correctly, so I don't think you can do that.

If you haven't already, try applying a push modifier with a small value (I assume you're on Max) to either your high or low poly-- there's a glitch in max which can cause problems like this in places where your high and low are perfectly coplanar.

r_fletch_r

jeremiah_bigley wrote: »

Everything is on renderable. I just checked the backface cull and that was not it.

I just tried what I suggested and it wont bake :poly142: If the other suggestions dont work you could try turning off shadow casting on the low poly. perhaps that'll remove it from the AO solution. Im guessing though as I cant test it.

kio

select the lowpoly mesh and hide all polygons might do the trick

Stromberg90

Are you using rtt assist by any chance?
I am wondering since this happends to me when using it for AO bakes.

boyluya

I'm also having issues like this. Anyone knows the solution? Thanks

jeremiah_bigley

mbullister wrote: »

I think that unchecking the renderable attribute prevents RTT from working correctly, so I don't think you can do that.

If you haven't already, try applying a push modifier with a small value (I assume you're on Max) to either your high or low poly-- there's a glitch in max which can cause problems like this in places where your high and low are perfectly coplanar.

Yeah I was pretty sure unchecking the renderable option would make it not render... I guess I was tired when I read r_fletch_r's response and I thought he meant to go double check and make sure that they were all checked.

As for the push modifier... Yeah I have experienced that coplanar issue before, but in this case they are not really coplanar. Maybe in the spots where they pass through each other... but the only way to prevent that would be to make sure my lowpoly floats completely outside of the highpoly. Which would be a pain in the ass.

I am going to give kio's method a shot.

kio wrote: »

select the lowpoly mesh and hide all polygons might do the trick

Interesting... I had heard of ppl doing this, but never tried it myself. Sounds like something that just wouldn't work. I will give it a shot though.

Stromberg90 wrote: »

Are you using rtt assist by any chance?
I am wondering since this happends to me when using it for AO bakes.

nope... ;/ I think it has to do with the coplanar issue mbullister was talking about. So really it would just come down to a work around? hmmm...

j_bradford

There's a few solutions I can think of;

Reset xforms on the high and low

Make sure the lowpoly is hidden from the actual render; in your mentalR AO material, "incl./excl. object ID (neg = exlude)", give that a negative number like -7. In your lowpoly object properties give it an object ID of 7.

The other solution is to export your high and low as obj files and import them into a new scene, recreate your render settings/materials.


This isn't related to your question, by try these settings for better looking results.

Samples : 300
Spread : 2.75
Max Distance : 0.0
Falloff : 1.0

r_fletch_r

Those settings are nuts. Your using AO to create a really really expensive and crap version of Final gather. If you want a map with broad smooth blocks of shadow then use a FG bake. its super fast and will give a similar result in a fraction of the time. you can recover small details by multiplying a cavity map over the FG.

j_bradford

I'm not sure if you're referring to my last post or not, but those settings are extremely fast to render in Max 2010+. We use AO for all sorts of things, and anything lower than 300 samples starts to show artifacts which can affect the method of how the AO is used. The spread when rendering characters really brings out all the details you sculpted in.

jeremiah_bigley

kio!

You are awesome! I set the visibility of the object down to 0 and that did the trick. Thanks guys!