Assign a Material to a Mesh

These snippets show how to assign a Material to a prim. The technical term in USD is to bind the material. The example here applies to any UsdShade.Material.

For more information on creating materials, see Create an MDL Material and Create a UsdPreviewSurface Material.

USD Python

This version creates a UsdPreviewSurface Shader and binds it to a mesh.

from pxr import UsdShade

def bind_material(prim, mtl):
    # Setup a MaterialBindingAPI on the mesh prim
    bindingAPI = UsdShade.MaterialBindingAPI.Apply(prim)
    # Use the constructed binding API to bind the material
    bindingAPI.Bind(mtl)


#############
# Full Usage
#############

from pxr import Sdf

stage = Usd.Stage.CreateInMemory()
default_prim = UsdGeom.Xform.Define(stage, Sdf.Path("/World")).GetPrim()

# Create a mesh plane from points and indices
points = [(0, 0, 0), (1, 0, 0),  (1, 1, 0),  (0, 1, 0) ]
indices = [ 0, 1, 2, 0, 2, 3 ]

mesh = UsdGeom.Mesh.Define(stage, '/World/plane')
mesh.GetPointsAttr().Set(points)
mesh.GetFaceVertexIndicesAttr().Set(indices)
mesh.GetFaceVertexCountsAttr().Set([3] * len(indices))

# Set the materials path
mtl_path = Sdf.Path(f"/World/Looks/PreviewSurface")
#Define the shader
shader = UsdShade.Shader.Define(stage, mtl_path.AppendPath("Shader"))
shader.CreateIdAttr("UsdPreviewSurface")
shader.CreateInput("diffuseColor", Sdf.ValueTypeNames.Color3f).Set((0,0,1)) 
shader.CreateInput("opacity", Sdf.ValueTypeNames.Float).Set(0.5)
shader.CreateInput("roughness", Sdf.ValueTypeNames.Float).Set(0.0)
shader.CreateInput("metallic", Sdf.ValueTypeNames.Float).Set(0.0)
shader.CreateInput("ior", Sdf.ValueTypeNames.Float).Set(1.0)

# Bind the material to the mesh
mtl = UsdShade.Material.Define(stage, mtl_path)
mtl.CreateSurfaceOutput().ConnectToSource(shader.ConnectableAPI(), "surface")

# Call our bind material function. Note that we are passing a prim, not a mesh.
bind_material(mesh.GetPrim(), mtl)