Baking AO with Mental Ray ...... HELL!!
polycounter lvl 13
Hi there again!
So I've been able to bake AO using the Skylight method in 3DS max 2012.:)
However, the results are not as good as Mental ray. The skylight method would always leave a light rim in corners using intersecting geometry. MR does not.
I've been experimenting with MR and the big trouble I'm having with it right now is that it isn't very reliable.:(
Sometimes, it works just as expected, but refuses to work properly on other occasions.
Here's an example, I'm trying to bake AO from a high rez model to a low poly model. When I render, the preview window shows red spots (Ray miss check). Despite adjusting the low poly cage, it does not seems to change the situation.
Even the "Hide the low poly model's faces" method did not work.
Now here's the freaky part, scaling the low poly model actually helps! It's as if the baking process no longer listens to the cage but to the geometry itself!
And to add to the mystery, the baked normal map and AO maps, on occasion come out right even if red spots (Ray Miss Check) are seen in the preview window.
The funny thing is that switching backing to the skylight method gives no trouble at all.
The good news is that MR AO baking works pretty well if it's just baking a low poly model onto itself.:\
Anyone care to share his/her thoughts?
I've also heard of an alternative to the cage method, can someone tell me about it?
thanks!
Regards
GIS3000
So I've been able to bake AO using the Skylight method in 3DS max 2012.:)
However, the results are not as good as Mental ray. The skylight method would always leave a light rim in corners using intersecting geometry. MR does not.
I've been experimenting with MR and the big trouble I'm having with it right now is that it isn't very reliable.:(
Sometimes, it works just as expected, but refuses to work properly on other occasions.
Here's an example, I'm trying to bake AO from a high rez model to a low poly model. When I render, the preview window shows red spots (Ray miss check). Despite adjusting the low poly cage, it does not seems to change the situation.
Even the "Hide the low poly model's faces" method did not work.
Now here's the freaky part, scaling the low poly model actually helps! It's as if the baking process no longer listens to the cage but to the geometry itself!
And to add to the mystery, the baked normal map and AO maps, on occasion come out right even if red spots (Ray Miss Check) are seen in the preview window.
The funny thing is that switching backing to the skylight method gives no trouble at all.
The good news is that MR AO baking works pretty well if it's just baking a low poly model onto itself.:\
Anyone care to share his/her thoughts?
I've also heard of an alternative to the cage method, can someone tell me about it?
thanks!
Regards
GIS3000
Replies
Either bake in scanline or Xnormal for several reasons (at least for AO):
1) Scanline doesn't create surface banding, which happens with MR on low settings.
2) MR requires ridiculous settings = Time needed for bake is ten fold.
3) Padding gets bad streaking.
I think I never once used MR for baking AO. I know I used xNormal, ZBrush and even VRay, but never once MR.
Oh wow, so it does stink that bad.......
Oh well. Thanks for the heads up!
Lauren's tutorial talked about it, ( www.laurenscorijn.com/articles/ambient-occlusion-baking ) so I'm kinda still looking.
Anyone else?
thanks again!
ohmygod yes.
for low-2-low AO i've started using lighttraces since xNormal keeps baking triangle edges into my occlusion maps.
EDIT: for baking High-2-Low with floaters in xNormal, check "discard backface" or similar, within the specific maps' settings.
So ... I do occasionally use mental ray for the AO if I'm in a hurry. The trick is to bake the normal maps using scanline first. Apply a standard material with the bump normal applied to your object. Then bake out the AO using Mental ray without the High Res object! No clipping, No cage errors, No Worries and all the normal detail.
Keep all the settings as default with the exception of those within the Render To Texture window. Samples to 100+ and Spread to 1.0; These are very simple settings that will get you something like an AO Map.
You can play with Spread, Max Dist and Falloff further to get better results. Best to test these first with a lower Res output and lower samples till you get something you like. Keep this as a broad AO Layer.
For finer detailed AO I would take the Displacement Map or Normal Map into something like Crazy Bump or again XNormal. Photoshops NDo isn't too bad either.
Blend the two or three in Photoshop.
Before I set off in a mad baking session I always ask myself is it quicker to paint by hand? Sometimes its just is!
Thanks!
No, you do not need to unwrap the UVs of the high res. Just the low res model.
hope this helps.