MelR wrote:
> Thank you to all who replied.  Leroy, how a normal is defined by the given
> sequence of triangle corners is something I've been looking for and have not
> previously been able to find.  Your definition is clear except for one detail:
> is the vector cross product a right or left-handed operation?  (Based on my
> limited familiarity with povray, I'm assuming it is a left-handed operation
> unless "right" has been specified, but I'm not certain.)

To tell the truth I don't know. I could never get my head around left or 
right handed operation when turning it into code. I remember spining a 
day or so playing with my figers,tring to turn them into triangles. It 
was silly. I said to myself forget it, the code it what I need. So by 
trial and error I got the code I needed for normals.
  Going over my old code I think with a triangle laying flat in the y=0 
plane that starting at one point and going anticlockwise gathering 
points the normal will point in the positive y direction.

> 
> I will try the texture definitions as you've described.  Here, too, I've not
> been successful in discovering where in the documentation these issues are
> clearly discussed as they relate to triangles with both front and back textures
> as part of a mesh.  I appreciate your effort to address this directly.
> 
3.4.2.3.1  Solid Mesh  in pov help file has a little.
I know there are some web sites out there that can be of help but I lost 
all my bookmarks in a computer meltdown, sorry.

> So far I have been using (flat) triangles and not "smooth triangles".  In my
> efforts to far, povray has detected some compilation?/syntax? errors, but I
> don't know yet if these are due to errors in my expressions or errors in my
> understanding as to how an interior_texture applies to a (flat) triangle.  If
> you are aware that these discussion do not apply to a (flat) triangle and I
> must use a "smooth triangle" instead, please let me know.
> 
The most common error with Mesh is dropping commas. When you drop one 
inside a vector sometimes, not always, Pov will expand the vector. That 
is if ya have <4.5,6.7> you'll get <4.5,6.7,0>.

There no difference when it comes to inside_vector between Flat and 
smooth triangle meshs.


Have Fun!













> I appreciate your assistance.
> Mel
>

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