Кластеры объектов надо объединить в группу, которой назначить нужный материал, дальше рули как хочешь.
Пример
NewScene
CreatePrim "Sphere", "MeshSurface"
ApplyShader , , , , siLetLocalMaterialsOverlap
CreatePrim "Torus", "MeshSurface"
SetValue "torus.torus.radius", 5
ApplyShader "Lambert", , , , siLetLocalMaterialsOverlap
SetDisplayMode "Camera", "shaded"
SelectObj "sphere,torus", , True
ActivatePolygonSelTool
AddToSelection "sphere.poly[0-15,48-LAST],torus.poly[0-15,48-LAST]", , True
CreateCluster
CreateGroup
SetValue "Group.Name", "Group_material"
ApplyShader "Material\Constant", , , , siLetLocalMaterialsOverlap
SetValue "Group_material.Material.Constant.color.green", 0.183
SetValue "Group_material.Material.Constant.color.green", 0.921
SetValue "Group_material.Material.Constant.color.red", 0.256
ActivateObjectSelTool
SelectObj "sphere", , True
SelectObj "sphere.polymsh.cls.Polygon.Material"
SetValue "Group_material.Material.Constant.transparency.green", 0.694
SetValue "Group_material.Material.Constant.color.green", 0.457