Simplify Blender shaders to a simple diffuse texture for export (written for GLideN64-Scene-Ripper)

simplify_shaders_for_export.py

# Fixes shaders from GLideN64-Scene-Ripper for OBJ/etc export.
# Instructions: select objects you want to fix, then run this
# script from the Text editor.
# Tested with Blender 3.6.

import bpy

# Whether to connect the diffuse texture's alpha to the
# Principled Alpha socket in the simplified material.
CONNECT_ALPHA = True

# Converts any material to a Principled BSDF material with a
# simple diffuse texture.
def simplify_material_for_export(material):
    if not material.use_nodes:
        return

    nodes = material.node_tree.nodes
    links = material.node_tree.links

    # Find one texture node to use as the diffuse texture
    tex_nodes = [
        node for node in nodes
        if node.type == 'TEX_IMAGE' and node.image
    ]
    # Simple heuristic to prefer 'Texture 0' to 'Texture 1'
    tex_nodes.sort(key=lambda node: node.label or node.name)
    tex_img = tex_nodes[0].image if tex_nodes else None
    do_color = tex_img and tex_nodes[0].outputs['Color'].is_linked
    do_alpha = CONNECT_ALPHA and tex_img and tex_nodes[0].outputs['Alpha'].is_linked

    nodes.clear()

    out_node = nodes.new('ShaderNodeOutputMaterial')
    pbr_node = nodes.new('ShaderNodeBsdfPrincipled')
    links.new(pbr_node.outputs[0], out_node.inputs[0])
    out_node.location = 300, 300
    pbr_node.location = 10, 300
    if tex_img:
        tex_node = nodes.new('ShaderNodeTexImage')
        tex_node.image = tex_img
        tex_node.location = -330, 250
        if do_color:
            links.new(tex_node.outputs["Color"], pbr_node.inputs["Base Color"])
        if do_alpha:
            links.new(tex_node.outputs["Alpha"], pbr_node.inputs["Alpha"])

obs = bpy.context.selected_objects
for ob in obs:
    for slot in ob.material_slots:
        if slot.material:
            simplify_material_for_export(slot.material)