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I have a car that has two materials assigned to it. When I apply a boolean modifier to the car it tweaks all the colors that were assigned to it.

Why is this and what can I do about it?

iKlsR
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BlendSwap
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1 Answers1

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This is because assigning different materials to a mesh is dependent on the Topology of the mesh.

Adding a Boolean operation changes the topology, so the faces that no longer exist can't have a material, and new faces will most likely be in different positions or shapes.

Blender assigns the first material to new faces created by a Boolean modifier:

boolean example materials

A few possible workarounds:

  1. Applying the Boolean modifier and assigning the materials your self, as well as changing the topology to fit where the materials should go.

  2. Using a texture to combine materials with a Mix shader, independent of the object topology.

    enter image description here

    enter image description here

gandalf3
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  • Here is the source for material assignment: http://wiki.blender.org/index.php/Doc:2.6/Manual/Modifiers/Generate/Booleans. "the modified mesh will receive its first active material index assigned to its new topology" – Charles HETIER Dec 04 '14 at 13:07