My materials are not showing up in the rendered view even though I assigned materials to them all

Question

At first, they worked properly, but now none of the props in my scene are showing any materials in the rendered view. They seem to show an impression of material instead, where they are not just smooth objects but rather bumpy, sort of.

More information is that each object in the scene is made of different parts which is joined together. I of course gave them each materials before joining them with cntrl + J. I even use the UV editor to modify the way the texture displayed. But now none of it is showing which is confusing. I do not know what I did wrong. Could someone please help me?

I have included a link to the file, too. Thanks.

Blender file

Answer 1

Looking at your blend file I'm 99% sure it's because you're doing something weird with the Ambient Occlusion map and the Base Color. Can't confirm because the node is lost between our different versions of Blender, but it should be set up with both nodes going into a Mix node, set to Multiply blend mode and the Factor at 1.0. Doing that it seems to fix it on my end.

Result:

Answer 2

The blend file data shows it was written using Blender v3.0.42. And yet when opening the file with that version, the MixRGB nodes in your materials are shown as being undefined:

This happens when a file was done on Blender versions from 3.4 and above, and then open in an older version of Blender from before 3.4. The issue with that being that the node was changed in version 3.4:

The "MixRGB" node for Shader and Geometry Nodes is converted to the new "Mix Node" on loading. Files saved with the new node are not forward compatible with older versions of Blender (bfa0ee13d5).

Note that it is possible to upgrade a file's mix node to a newer version, but not to downgrade. So the issue occurs only when opening newer files with older versions than 3.4.

If you have a version of your file that wasn't saved with a Blender version <3.4, you could use that. Otherwise, you have to go through each of your materials and replace the undefined nodes by the available Mix node.

I made a script that should theoretically be able to do it in one click, but it will not recover the mix type nor input values. It will only preserve the old socket color inputs/output connections, and assuming you used most of these mixRGB as multipliers between albedo and ambient occlusion: it arbitrarily sets the mix nodes to multiply and the factor at 1. You can change that if you want another set of... Settings... It's below the "EXTRA OPTION" comment.

But if you don't have most of your nodes doing that albedo multiply AO, then perhaps a more neutral script that just connects all nodes as is and leaves unconnected values at default is better, in which case see this other answer.

import bpy

for material in bpy.data.materials:
    if not material.use_nodes:
        continue

    node_tree = material.node_tree
    nodes = node_tree.nodes
    
    fail_state = False

    for node in nodes:
        if node.name == "Mix":
            try:
                input_links = {}
                output_link = None
                
                if len(node.inputs) > 6 and node.inputs[6].is_linked:  # Color1 input
                    input_links[6] = node.inputs[6].links[0].from_socket
                if len(node.inputs) > 7 and node.inputs[7].is_linked:  # Color2 input
                    input_links[7] = node.inputs[7].links[0].from_socket

                if len(node.outputs) > 0 and node.outputs[2].is_linked:
                    output_link = node.outputs[2].links[0].to_socket

                mix_rgb_node = nodes.new(type="ShaderNodeMixRGB")
                mix_rgb_node.location = node.location
                # EXTRAS OPTIONS
                mix_rgb_node.blend_type = 'MULTIPLY'
                mix_rgb_node.inputs[0].default_value = 1 # Factor

                if 6 in input_links:
                    node_tree.links.new(input_links[6], mix_rgb_node.inputs[1])  # Color1 input
                if 7 in input_links:
                    node_tree.links.new(input_links[7], mix_rgb_node.inputs[2])  # Color2 input

                # Reconnect the output link to the new MixRGB node's Color output
                if output_link:
                    node_tree.links.new(mix_rgb_node.outputs[0], output_link)

                nodes.remove(node)
            except:
                print(f"failed on material '{material.name}'")
                fail_state = True

print(f"Replacement of 'Mix' nodes with 'MixRGB' nodes completed {'with errors' if fail_state else 'with no errors'}.")

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