Bug in E3Triangle_InterpolateHit

[Roger H. <rog...@mi...>]

There is a bug in E3Triangle_InterpolateHit when it is asked to return 
a normal vector.

It should return a normal in world coordinates, and if there are no 
normals in the
attribute set of the surface, nor in the attribute sets of the vertices 
then all is well.

When there are normals then it takes these (which are in local 
coordinates) and
does some averaging of them and then returns them as if they were in 
world
coordinates.

I have fixed this in my version of Quesa by passing the view into 
E3Triangle_InterpolateHit
and then calling Q3Vector3D_Transform where appropriate. I also have to 
include E3View.h
in E3Utils.c so I can get the transform using 
E3View_State_GetLocalToWorld.

Is this OK?
Should I pass in the matrix instead?
Should it return a flag to say if the normal is in world or local 
coordinates and then
fix it in the calling code (2 places)?
Should it pick it up in some other way?


Also, when the normal is calculated from three vertex normals, it can 
result in a
normal which is not normalised. Is there any good reason for this or 
can I
normalise it?

Roger.