color Displacement map problem.
 

Hey - so i'm using maya 09 and i'm trying to get my color map working with my displacement map on this model.

for some reason when i add the color map it doesn't render properly. i don't think it's a problem with the UVs - as you can see it looks fine in the view port.

i've noticed that if i adjust the settings in the approximation editor for displacement tessellation and subdivisions - it seems to move the color map - as you can see in the bottom 2 pictures.

i'm kind of confused as i don't see why this should affect the color map... i've tried deleting history and everything else i can think of....what am i doing wrong?? :(

Hi Arran,

Not too sure what the problem might be, i've not rendered a displacement from Z for a while, Jay had a post in the rendering thread about Z and maya 08 which might be helpful for you to have a look at.

It may be that its messing up the UV's in someway when the sub'd's being applied??

hey gster - thanks mate - yeah - i think your right - it's like the UVs are being moved by the approximation editor - yet they still look fine in the texture editor. It doesn't seem to happen in maya 7 so i wonder if it's a bug.

What happens when you smooth the low poly in maya, are the UV's screwed up then?

Just that I've had a couple of things "alter" the UV's after emoothing that I thought would have preserved the UV space but didnt. Untill I switched it off in the smooth Mesh options.

Maybe theres an option in the sub d approx (or it might derive it from maya?)

thanks gster - when i tried smoothing, the UVs stayed in the same place in the texture editor, but when i rendered it went from looking like the bottom image to the middle image.

i looked at the smooth mesh options, but they were already turned off and telling it to derive from maya in the subdivision settings just had the same effect.

I tried rendering my frog with the exact same settings from maya 7 (which renders fine) and the same thing happened. the only workaround that i've found so far is to set the filter type to off on the color file and that seems to render it fine - tho i'm not sure how this affects the quality of the file.

hmmm...

ok - just got a response from hezza on cgsociety. here's his solution -

'Its a known problem with the Catmul Clark subdivision method that was introduced in 8.5, I really don't understand how anyone actually uses mental ray displacement in production without switching it back to the old division method

If you type

addAttr -ln "miExportCCMesh" -at bool mentalraySubdivApprox1;

the problem will go away, but you loose all the memory/speed improvements that the CCmesh method is meant to give us.

Please please report this as a bug to autodesk, its getting a joke this hasn't been fixed in 3 releases.'

haven't tried it yet as i'm at work.

Ahhh!!

Nice one, yeah I remember the intro of the catmull clarke method, it was introduced so that MR would render non-ngon sub-d's if I remember rightly.

Cheers

Arran!