Bmesh: how can I import custom vertex normals

Question

I have a question concerning BMesh and custom vertex normals editing. At the moment I am writing a little blender importer for a custom data format and I am stuck with importing/manipulating custom vertex normals. I am using the bmesh module because I want to use it's functionalities before transforming the bmesh into a real mesh.

Can anyone tell me if it is possible to set the normals with bmesh? Do I need to import them with the Mesh module?

Thanks a lot in advance for any tipp!

probably related: http://blender.stackexchange.com/questions/32292/is-there-a-way-to-create-per-face-per-vertex-normals — Mutant Bob, Mar 24 '16 at 14:58
thanks. I will most definately have to do it with the mesh module instead of bmesh. Bmesh just offers so much more functionality to work with... — Madlaina Kalunder, Mar 25 '16 at 20:22

score 2 · Answer 1 · edited May 05 '16 at 09:26

2

I believe since Blender 2.74, this was made possible for the bpy Mesh type. You can use the mesh normals_split_custom_set method to do this.

In this example, I only have per-vertex normals so I create a new list with one normal corresponding to each loop.

normals2 = []
for l in mesh.loops:
    normals2.append(normals[l.vertex_index])
mesh.normals_split_custom_set(normals2)
mesh.use_auto_smooth = True

Note that auto smooth needs to be enabled for this to work.

In my case, I could have used the normals_split_custom_set_from_vertices method, and passed in normals directly.

edited May 05 '16 at 09:26

Ray Mairlot

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answered May 05 '16 at 03:42

Petar

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Yes, thats what I am doing now. Thanks. I WANT to use the Bmesh module though because of it's functionalities. Vertex normals are not supported (yet) though - it turns out - and the information gets lost if you transform the mesh to bmesh. – Madlaina Kalunder May 08 '16 at 10:49

score 0 · Answer 2 · answered Mar 23 '16 at 15:10

0

It is probably as simple as

mesh = obj.data
bm = bmesh.new()
bm.from_mesh(mesh)

bm.verts[i].normal = [ x,y,z]

bm.to_mesh(mesh)

answered Mar 23 '16 at 15:10

Mutant Bob

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Thanks for your suggestion, sadly it's not that easy since I need to set the normals per face loop (one vertex can habe multiple normals, which is the whole purpose of split normals) – Madlaina Kalunder Mar 24 '16 at 12:44
The few things I have read imply that blender does not fully support per-face vertex normals yet. I don't know if it is on the roadmap. – Mutant Bob Mar 24 '16 at 15:01
2

And even setting per-vertex normals seems to be ineffective. You can even do obj.data.vertices[0].normal = [1,0,0] and the value will be reset to default if you go in and out of edit mode. – Mutant Bob Mar 24 '16 at 15:12

Bmesh: how can I import custom vertex normals

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