Scripting Mentalray Batch Bake

[bastien.laby]

Hello everybody and thanks for your attention.

On the one hand I have a Maya scene which contains complex nodal materials.

Example :

On the other hand I have a personnal OpenGL rendering application. In order to interpret these complex materials in my application, I want to bake them using "Mentalray Batch Bake".

I can do it manually, by :

1) Select the material and the related mesh

2) Go to panel Rendering --> Lighting/Shading --> Batch Bake (mental ray)

3) Fix the baking parameters and "Convert"

This operation creates a new simpler material that I can deal with :

Now, what is the problem ?
It turns out that I fact, I don't have 1 complex material but several, and I don't have only 1 scene but several. So I have a lot a complex materials in different scenes. I want to write a script that do the previous process automatically.

Operation 1) is easy to reproduce, but I'm having trouble for operation 2). In order to do this, I looked the command output an try to reproduce these :

Command output :

select -r MyUberMesh1 MyUberMesh2;
select -tgl myUberShader ;
convertLightmapSetup  -camera persp -bakeSetOverride tmpTextureBakeSet -showcpv;
// Baking 2 maps // 
// Cmd: convertLightmap  -camera persp -bo tmpTextureBakeSet shadingEngine myUberMesh1 shadingEngine myUberMesh2 //
// Baked 2 maps. 0 maps failed //

My script to reproduce it :

# Create a baked set
maya.mel.eval("createNode textureBakeSet -n "myUberBakedTexture"")
maya.mel.eval("setAttr ...") # Set baked set attributes as needed

# Select the material and the related meshes
cmds.select("myUberMaterial")
cmds.hyperShade(objects="")
selected_meshes = cmds.ls(sl=True, l=True)
cmds.select("myUberMaterial", add=True) # Because the hyperShade command unselected it

# Do Batch baking using converLightmap command
shading_engine = get_shading_engine("myUberMaterial") # Personnal function
melcmd = "convertLightmap -camera persp -bo "myUberBakedTexture""
for msh in selected_meshes :
    melcmd += " " + shading_engine + " " + str(msh)

maya.mel.eval(melcmd)

Finaly, the command I call is like :

convertLightmap -camera perp -bo myUberBakedTexture shadEngine Mesh1 shadEngine Mesh2 ...

 
The problem is that the command has not the same effect that the one I want to reproduce. The one I want to reproduce create a new simple material and attach the related meshes to it, and the command I write myself do not create a new material, and do not attach related meshes to it.

Is someone who has already used this command could help me on this way ?

Thank you and sorry for my long post.