txel colorization with spot vector (source of light)

[FredOden]

This doesn't behave normally :

• could come from the surface orientation ...
• could come from the demo ?

[FredOden]

On the way to solve ... Colorize from absolute value of Scalar product of txel normal vector .and light vector.
Now have to manage shade to "blackify" parts in the shade of another point...
That's another story...