Re: [Visualpython-users] Coloring faces

[Bruce S. <Bru...@nc...>]

Here's the crucial statement from the Visual help description of the 
faces object (choose "Visual" on the Help menu in IDLE):

    If you don't specify normals at the vertices,
    the face is illuminated only by "ambient" light.

Because you had set the background color to white, the parallelogram 
looked completely black but was actually colored, but only dimly, due 
solely to ambient light. Here is a version of your parallelogram routine 
which constructs the necessary normals:

def parallelogram(v1,v2,v3,trianglecolor):
     c = color.hsv_to_rgb(trianglecolor)
     n = norm(cross(v2-v1,v3-v1))
     triangle1=faces(pos=[v1,v2,v3],normal=n,color=c)
     triangle2=faces(pos=[v2,v2+v3-v1,v3],normal=n,color=c)
     triangle3=faces(pos=[v2,v1,v3],normal=-n,color=c)
     triangle4=faces(pos=[v2+v3-v1,v2,v3],normal=-n,color=c)

The information about built-in colors is in the Help; see "Specifying 
Colors". The module itself has the file name "crayola" but one actually 
says "color.orange", not "crayola.orange".

Bruce Sherwood

Poul Riis wrote:
> I can't extract from the manual how to control the color of the faces
> object. The attached example works, but the rectangle always has the same
> color, no matter the trianglecolor parameter. In fact, I would like to
> make the back side of the rectangle somewhat darker than the front side -
> automatically.
> 
> Btw - where can I find information about crayola colors?
> 
> Yours,
> Poul Riis