Primitive normal

[Macha]

Is there a way to access the primitive normal? We can visualize it, but is there a way to get at it? There is a vop node but it requires uv's. Is there a simpler way, like $N for primitives?

[graham]

You can use a prim() expression to get it like any other attribute.

prim("/obj/geo1/file1", 0, "N", 1)

You can also use Python.

hou.Prim.normal()

Edited July 9, 2010 by graham

[tjeeds]

The fact that the Primitive Normal VOP wants uvs doesn't mean they have to be meaningful. Because it's the primitive normal it is not interpolated across the face, so it's the same no matter what uv position you give it. The Primitive Attribute VOP does interpolate over the face based on uvs so you can use it to return interpolated point normals or positions. In the attached file you can see all this in action, by changing the u and v sliders you'll see the point position change but the normal remains constant at any uv position on the face. Hope that helps

getting_primN.hip