Transfer Vertex Normal Value between different vertexes in different meshes, need help!

Coding
,
#1

Hello everyone,
In order to making 2 meshes seamless between them, I’m coding a tool to transfer(copy) Vertex Normal Value between different vertexes in different meshes.
First, I get the Vertex Normal Value by MFnMesh.getVertexNormal() method in world space from the source mesh’s vertex. Then, using the normal value above, I set the Vertex Normal Value by MFnMesh.setVertexNormal() method in world space to the target mesh’s vertex. The source and target mesh vertexes are in the same position. I think, with the same vertex normal value, the seam between 2 vertex meshes will disappear. But it doesn’t! I display the vertex normal in Maya and find that the normal direction of two vertexes are different, it’s a very small different!
How could I fixed the difference? Or what’s wrong with my solution?
Thank you very much.
Yours,
Yixiong Xu
2019.11.14

#2

If I were to guess I would say that it’s because the normals returned from getVertexNormal are calculated on the fly. According to the documentation:

So I would try the getFaceVertexNormal and setFaceVertexNormal methods.
Possibly, you could use getVertexNormal, then set all the face-vertex normals of both meshes to that value.

#3 
def copyNormal(self):
    vertex =mc.ls(sl=1,fl=1)
    global vertexNormal
    vertexNormal=mc.polyNormalPerVertex(q=1, xyz=1)

def pasteNormal(self):
    vertex =mc.ls(sl=1,fl=1)
    mc.polyNormalPerVertex(xyz=(vertexNormal[0],vertexNormal[1],vertexNormal[2]))

I used copy and paste and I hope that helped you

2 Likes
#4

Hello StrongBread,
Thank you for your solution, it works for me!
But I want to know what happened behind the command polyNormalPerVertex. It really interests me!
How can I use maya python api to get the same result?
Yours,
Yixiong Xu
2019.11.15

#5

Hello tfox_TD,
Really thank you for your explanation.
Unfortunately, I try the getFaceVertexNormal and setFaceVertexNormal method. But it fails.
As StrongBread’s reply, his suggestion really works for me.
I want to know what happened behind the maya.cmds.polyNormalPerVertex command, do you know it?
Anyway, thank you again for your explanation about the difference between vertex normals.
Yours,
Yixiong Xu
2019.11.15

#6

http://download.autodesk.com/global/docs/maya2013/zh_cn/CommandsPython/polyNormalPerVertex.html
If you look at the documentation, I guess I just replaced the vector data, and I don’t know any more!