normals_split_custom_set() does not behave as documented #44359

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Gaia Clary · 2015-04-12T10:39:48+02:00

Gaia Clary commented

2015-04-12 10:39:48 +02:00

The script below creates an array of zero entries, converts the array into a list of tuples,
then it calls the function normals_split_custom_set().
According to the documentation:

  normals_split_custom_set(normals)  
     Define custom split normals of this mesh
     (use zero-vectors to keep auto ones)
     Parameters:	
     normals (float array of 3 items in [-1, 1]) – Normals

So i expect that when i use a list of zero vectors, then the mesh should not change at all,
but actually it changes a lot. Here is the blend file quarter_ring_custom_normals.blend and here is the script:

  import bpy
  ob   = bpy.context.object
  mesh = ob.data
  normals = [0.0] * len(mesh.loops) * 3

  bpy.ops.object.mode_set(mode='OBJECT')
  tnormals = tuple(zip(*(iter(normals),) * 3)) 
  mesh.normals_split_custom_set(tnormals)
  bpy.ops.object.mode_set(mode='EDIT')

I am not even sure if this is a bug or just a lack of knowledge on my side.
But i could not find any information for the case where i want to
keep almost all normals as they have been calculated by Blender and
just add some corrections for a few normals.

The script below creates an array of zero entries, converts the array into a list of tuples, then it calls the function normals_split_custom_set(). According to the documentation: ``` normals_split_custom_set(normals) Define custom split normals of this mesh (use zero-vectors to keep auto ones) Parameters: normals (float array of 3 items in [-1, 1]) – Normals ``` So i expect that when i use a list of zero vectors, then the mesh should not change at all, but actually it changes a lot. Here is the blend file [quarter_ring_custom_normals.blend](https://archive.blender.org/developer/F161156/quarter_ring_custom_normals.blend) and here is the script: ``` import bpy ob = bpy.context.object mesh = ob.data normals = [0.0] * len(mesh.loops) * 3 ``` ``` bpy.ops.object.mode_set(mode='OBJECT') tnormals = tuple(zip(*(iter(normals),) * 3)) mesh.normals_split_custom_set(tnormals) bpy.ops.object.mode_set(mode='EDIT') ``` I am not even sure if this is a bug or just a lack of knowledge on my side. But i could not find any information for the case where i want to keep almost all normals as they have been calculated by Blender and just add some corrections for a few normals.

Gaia Clary commented

2015-04-12 10:39:48 +02:00

Changed status to: 'Open'

Bastien Montagne was assigned by Gaia Clary

2015-04-12 10:39:48 +02:00

Gaia Clary commented

2015-04-12 10:39:48 +02:00

Added subscriber: @GaiaClary