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Crash when entering edit mode with a lot of meshes selected
Closed, ResolvedPublic


System Information
Operating system: windows 7
Graphics card: GTX 1660

Blender Version latest 2.81 and 2.852

I select multiple meshes in the attached porte13.blend file and enter edit mode : crash in most cases

This crash dosen't happen with Blender 2.80

Event Timeline

Philipp Oeser (lichtwerk) lowered the priority of this task from Needs Triage by Developer to Confirmed, Medium.Tue, Oct 22, 2:00 PM

Can confirm.

getting this on open

ERROR (bke.modifier): /blender/source/blender/blenkernel/intern/modifier.c:410 modifier_setError: Enable 'Auto Smooth' option in mesh settings

getting this on entering editmode

BLI_assert failed: /blender/source/blender/gpu/intern/gpu_element.c:197, GPU_indexbuf_set_tri_verts(), at '(elem + 1) * 3 <= builder->max_index_len'


Philipp Oeser (lichtwerk) lowered the priority of this task from Confirmed, Medium to Needs Information from User.Tue, Oct 22, 2:44 PM

There is something wrong with the material indices of some meshes.

You can run this script to correct this:

import bpy
for ob in
    if is None or ob.type != 'MESH':
    not_valid =
    if not_valid:
        print("mat indices not_valid ",
        print("mat indices valid ",

output will be [just the bad ones]:

mat indices valid  screw_Plate_01.000
mat indices not_valid  screw_Plate_01.001
mat indices not_valid  screw_Plate_01.003
mat indices not_valid  screw_Plate_01.005
mat indices not_valid  screw_Plate_01.008
mat indices not_valid  screw_Plate_01.009
mat indices valid  screw_Plate_01.012
mat indices not_valid  screw_Plate_01.013
mat indices not_valid  screw_Plate_01.014
mat indices not_valid  screw_Plate_01.015

Now the question is: how did we get here?
This might be because of a recent bug blender had about multiple materials...
(if this is the case then you should run that script and you should not any errors/crashes anymore)

If these errors show up again after you have cleaned the file, we would need to know which operations caused this to happen? Any idea?