Ron Parker wrote:
>						    The best understanding
> I've been able to formulate for a bicubic patch is that the four corners
> of a patch are always on the surface of the patch.  The other eight edge
> points are "control points" analogous to the "handles" on Bezier curves
> in programs like Corel Draw, Freehand, or Illustrator in that they define
> the beginning and ending direction of the curves that define the edges of
> the patch, as well as the "tension" at the corners.  These eight points
> also specify the surface normals at the four corners, sorta indirectly.
> 
> The four points in the middle of the patch are the hardest to understand,
> but I tend to visualize them as the same sort of "control points," except
> that the "anchors" they are associated with are not actually on the
> surface of the patch.  In a sense, they control how the surface slopes
> away from the edge curves, though their exact effect might not be
> immediately or intuitively obvious.

Thanks. This makes bicubics less intimidating.

Post a reply to this message