Vertex Baking With Mr

[andy-davis]

I'm trying to get my head round the convertLightmap function.
The thing I don't get is why you have to send the function a shading group.
I've got objects in my scene with multiple shading groups, so if I was writing a batch script, do I have to check the SGs on each object and do a convertLightmap operation for each shading group?
Sounds like a tedious thing to do!

[joojaa]

Well your reading functionality, a bit off. The maya software baker does need a shading group but the mr baker does really not*.

Anyway this is bundles in teh bake sets functionality. Wich you might find a bit easier to handle. So you might just use that instead.

*for mr you can just assign all sgs to the list.

THe purpose is so that mentalray can export different maps for different regions of the mesh So you might after all want the hand rendered seperately to a mep, wheras you might also want to put them all in one map. So the command needs a way to be mofe verbose then the gui is. Flexibility allways convolutes things.

[joojaa]

Anyway what YOU REALLY want is to make a area light then assign it with the ambient occluison shader (under mentalray), then set its shape to user and put disable all maya shaders. Then adjust the ambient occlusion shader for intensity add any other lights and just. choose the lights only option and chek enable shadows and viola it does what you want.

Like i said its built in its just a question of how you apply occlusion as light or as texture. MAya cannot after all bake it as light unless you ASSIGN it as light.

[rgkovach]

i haven't tried JooJa's method, but here is a simple script i wrote to automatically manage and bake ambient occlusion.

CODE
{
    $curSel=ls -sl;

    if (!pluginInfo -q -l Mayatomr);
    {
        loadPlugin -qt Mayatomr;
    }

    if (!objExists mentalrayGlobals)
    {    
        createNode "mentalrayGlobals" -n "mentalrayGlobals";
    }

    // Create a bake set with the appropriate settings
    if ( objExists OcclusionSet == 0 )
    {
        $bakeSetAO=createBakeSet OcclusionSet vertexBakeSet;

        setAttr OcclusionSet.colorMode 3;
        setAttr OcclusionSet.occlusionRays 256;
        setAttr OcclusionSet.occlusionFalloff 500;
        setAttr OcclusionSet.normalDirection 1;
        setAttr OcclusionSet.orthogonalReflection 1;
        setAttr OcclusionSet.bakeColor 1;
        setAttr OcclusionSet.bakeAlpha 0;
        setAttr -type "string" OcclusionSet.colorSetName "COLOR1";
    }

    // Mental Ray expects an initial Vertex and Texture Bake Set or else it complains, so create them.
    if ( objExists initialTextureBakeSet == 0 )
    {
        createBakeSet initialTextureBakeSet textureBakeSet;
    }

    if ( objExists initialVertexBakeSet == 0 )
    {
        createBakeSet initialVertexBakeSet vertexBakeSet;
    }

    // Assign the shape nodes to the bake set created earlier.
    for ( $eachObj in $curSel )
    {
        string $shape[]=listRelatives -s $eachObj;
        sets -forceElement OcclusionSet $shape[0];
    }

    // Do the baking on the selected Objects.
    select -r $curSel;
    catchQuiet ( convertLightmapSetup  -camera persp -sh  -vm -showcpv );
}