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I try to remove all the faces of different objects that have a certain material assigned to its face. But I can't get the select part to work.

import bpy import bmesh scene = bpy.context.scene mat1 = bpy.data.materials['c1'] #This is the material name that I want for ob in scene.objects: #For all objects if ob.type == 'MESH': for mat in ob.material_slots: if mat.material == mat1: bpy.ops.object.editmode_toggle() mat.material.material_slot_select() # This doesnt work and i dont know if the later code work aswell me = ob.data bm = bmesh.from_edit_mesh(me) faces_select = [f for f in bm.faces if f.select] bmesh.ops.delete(bm, geom=faces_select, context=5) bmesh.update_edit_mesh(me, True) else: ob.select = False

What is wrong, what shall I write?

Br

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  • $\begingroup$ You can select faces based on material with Shift G > Material in edit mode.. $\endgroup$ Commented Jan 28, 2015 at 7:27

2 Answers 2

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import bpy import bmesh mat_c1 = bpy.data.materials['c1'] for ob in bpy.context.scene.objects: if ob.type == 'MESH': # get all the slot indexes to which mat_c1 is assigned c1_slots = [id for id, mat in enumerate(ob.data.materials) if mat == mat_c1] # you can also change active_material with # ob.active_material_index = some_number # and then run operators to deselect all faces and select material with # bpy.ops.material_slot_select() # but operators are bad so we will do it differently faces_mat_c1 = [] bm = bmesh.new() bm.from_mesh(ob.data) # no need to swith into edit mode for face in bm.faces: if face.material_index in c1_slots: # face has mat_c1 assigned faces_mat_c1.append(face) # delete faces with mat_c1 bmesh.ops.delete(bm, geom=faces_mat_c1, context=5) bm.to_mesh(ob.data) bm.free() else: ob.select = False
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  • $\begingroup$ thank you for a really helpful answer! It worked perfectly! $\endgroup$ Commented Jan 28, 2015 at 10:22
  • $\begingroup$ Glad it helped, you can mark it as correct for others to know, thx.) $\endgroup$ Commented Jan 28, 2015 at 10:38
  • $\begingroup$ @JaroslavJerrynoNovotny I want to go over all materials and select (or get indices of) faces to which that specific material has been applied to, without using bmesh (if possible). I haven't been able to find a good solution for doing that as of now. I would appreciate if you can take a look at my question here and see if you can offer a solution? $\endgroup$ Commented Mar 17, 2018 at 4:54
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Excellent question and answer. If you are changing a single object, this code should help.

This code is a script that changes the size of the UV layer of the selected active material's UV.

For Blender 3.2

import bpy import bmesh factor = 1.01 # Get the active material for the object obj = bpy.context.active_object mat = obj.active_material savemode = str(bpy.context.mode) if savemode == "EDIT_MESH": savemode = "EDIT" bpy.ops.object.mode_set(mode='EDIT') obj = bpy.context.active_object mat_c1 = mat c1_slots = [id for id, mat in enumerate(obj.data.materials) if mat == mat_c1] me = obj.data bm = bmesh.new() bm = bmesh.from_edit_mesh(me) uv_layer = bm.loops.layers.uv.verify() # currently blender needs both layers. bm.faces.layers.face_map.verify() # scale UVs xfactor for f in bm.faces: if f.material_index in c1_slots: for l in f.loops: l[uv_layer].uv *= factor bmesh.update_edit_mesh(me) bpy.ops.object.mode_set(mode=savemode)
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