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pythongraphics3dblender

How to set object surface to Background in Blender with Python API

How to set object's material surface to Background in Blender using Python API?

Desired output (UI)

I can only do achieve this in UI:

enter image description here

My code (that doesn't work)

I used this method

obj = ut.import_objects("models/bbox.fbx")[0]  # custom import function
color = (1., 0., 0., 1.)

mat = bpy.data.materials.new("mat")
mat.use_nodes = True
nodes = mat.node_tree.nodes

nodes.clear()
node_background = nodes.new(type='Background')
node_background.inputs[0].default_value = (0,1,0,1)

obj.data.materials.append(mat)

Output

Error: Python: Traceback (most recent call last):
  File "/blender_debug2.py", line 40, in <module>
RuntimeError: Error: Node type Background undefined

What does work

Changing the surface to Principled BSDF does work. But mat.node_tree.nodes does not contain the "Background" key.

def change_color(obj: bpy.types.Object, color):
    mat = bpy.data.materials.new("mat")
    mat.use_nodes = True
    principled = mat.node_tree.nodes['Principled BSDF']
    principled.inputs['Base Color'].default_value = color
    obj.data.materials.append(mat)
Solution

  • It seems like you were on the right track, for nodes you can find the background property within ShaderNodeBackground so the actual code would look more like

    obj = ut.import_objects("models/bbox.fbx")[0]  # custom import function
color = (1., 0., 0., 1.) # red

mat = bpy.data.materials.new("mat")

mat.use_nodes = True

if mat.node_tree:
    mat.node_tree.links.clear()
    mat.node_tree.nodes.clear()

nodes = mat.node_tree.nodes
links = mat.node_tree.links

output = nodes.new(type='ShaderNodeOutputMaterial')
shader = nodes.new(type='ShaderNodeBackground')

nodes["Background"].inputs[0].default_value = color

links.new(shader.outputs[0], output.inputs[0])

obj.data.materials.append(mat)