Max AO Bake error

Pope Adam

yo!

sometimes when i bake an AO map from my high poly model down to my low in 3DS Max, I get these big black areas of error where the two meshes are intersecting each other. The parts of the high poly that stick through my low poly mesh end up being mapped correctly by the AO, but any parts of the mesh that fall within the inside of the low poly mesh dont recieve any lighting information.

I've only seen this sometimes. I've had many successful AO bakes where this never occurred, whether or not the two meshes intersected each other or not - so I'm assuming that there's a checkbox somewhere that I need to track down and that someone on here will know exactly what setting that is.


Any idears?

MoP

Try turning off Cast Shadows in the Object Properties of your lowpoly mesh. Although, the scanline renderer automatically ignores the lowpoly unless you tell it otherwise (the "include working model" checkbox). Are you using Mental Ray?

Pope Adam

Well I don't have an example right now, the guy in the office next to me at work was the one having the problem, although I've had a simliar problem myself in the past.

As far as he knows it was doing a scanline render, but there was a thing that was happening before the render began... a popup window showed up with a progress bar. The windows was called "Raytrace Engine Setup"... the two progress bars were labeled "Total Progress" and "subdividing array" ... I don't recall ever seeing those bars show up when I did AO bakes..

Perhaps he accidentally turn on Raytrace or something? Thus causing the AO errors?

Mark Dygert

In addition to what MoP is suggesting, you can also go down into the element mode of the low poly object and "Hide All" then bake. That is if you're just trying to capture the high poly AO and bake it to the low.

glynnsmith

I've also had this problem, and neither of the above helped, oddly enough Max 2009 SP1.

I did find a funny workaround though, which was assigning a 0% opacity material to the low poly :P

nezach

For mental ray you can exclude geometry from the AO calculation by ID number. In the properties set the Object ID to a non zero number, then in the shader put the ID in the "Include Exclude ID" slot with a negative sign in the front.

The Raytrace Engine Setup window does indeed appear when the scanline hits a raytrace tag. The scanline doesn't do shader AO, but there are a lot of AO type hacks involving a skylight or a sky dome rig. Perhaps he was using one of those and calling it AO?

Pope Adam

Thanks fellas, I'll pass this thread on to my comrade, and/or refer back to it next time I have this problem.

cman2k

In my experience this problem has nothing to do with accidentally using the wrong settings, and everything to do with Max being stupid sometimes. I have fixed this problem by deleting my projection modifier, resetting xforms on my lowpoly and simply setting up the projection again.

I'm sure the workarounds posted also work. Just saying.... this isn't an "oh I made a mistake somewhere" kinda problem, just something went wrong along the line with the object that can only be fixed by collapsing and killing that bad data. :P

Drav

Sorry for horrendous thread revival, but this thread just saved my ass (well my bake anyway ) and I wanted to say thanks!

Pope Adam

LOL BACK FROM THE DEAD!! PC is the best