Updating Normals On A Custom Deformer Node

[oweber]

Hi,

I am writing a custom deformer node (MPxDeformerNode).
My deform function calculate the deformed position of each vertex but in addition I want to update the deformed vertex normals.

How can I update normals in the deform function?

Is it possible to get an MMeshFn for the outputGeom and than use setVertexNormals?

Thanks!

[videohead]

QUOTE(oweber @ 01/08/09, 11:21 PM) [snapback]298460[/snapback]
... in addition I want to update the deformed vertex normals.

While it may (note, may) be possible to set a vertex normal independent of the faces that share the vertex, I would strongly advise against this. I suggest that your deformer compute the position of the vertexes such that their normals equal the values you desire. Furthermore, because a vertex's normal vector is computed from the normals of the faces that share it, all vertex normals will automatically updated post deformation.

I could go into further detail that could potentially be of help, but I'm not sure if that's what you need. You might have to explain what you're trying to achieve.

[oweber]

Thanks for the reply.

I am not interested in automatic computation of the normal vector from the surronding faces.
My algorithm use a suphisticaed method for space deformation. I want to apply special transformation to the normals according to my own formulas.

My question is very technical. I don't know how to access the normal at vetex-face from within the deform() method. I can only use the geometry iterator to set positions but not normals.

[joojaa]

QUOTE
all vertex normals will automatically updated post deformation.

Not if they are locked.

QUOTE
I don't know how to access the normal at vetex-face from within the deform() method. I can only use the geometry iterator to set positions but not normals.

Read manual page of MFnMesh

But reaslly you dont want to inerit this form a deformer, the deform method just creates undue overhead for you.

[oweber]

I know about the "setNormal" functions that's available in MFnMesh. The problem is that I couln't get a valid Fn for the output mesh. Can you explain how to get it right?

What alternative are you recommend beside deriving from MPxDeformerNode?

Thanks

[joojaa]

MpxNode, anyway deformers are mpxNodes so if you dont implement deform and do implement compute instead youlld be fine. Deform is juts a convenience function for those who just want to move points, most of the time you'll notice it doesn't really do what you want because you are in sense not making a simple deformer,