- posted
18 years ago

many of the splines from Alias are not just curvature continuous, but that

the curvature changes smoothly. I'm having a heck of a time trying to match

that characteristic with SW04.

Checking the curvature combs, several of the splines look exactly like

straight lines and radius sections joined by short splines. If I simplify

the original spline I get smooth curvature, but it has reverse curvature

areas where the straight and arced sections join the short splines and areas

where the curvature is quite different from the original.

If I try to build my own curve with straight lines, radii and splines, I

can't seem to get the splines to smoothly transition to no curvature

straight lines and small curvature radii. Two point splines don't match the

original spline and the curvature is discontinous at the ends. Three points

splines can match the spline fairly well but also have discontinuous

curvature. With four point splines I can get close enough to continuous

curvature, but the transition isn't smooth. Adding more points, I don't seem

to be able to make the transition any smoother.

I seem to get the closest by making my own single spline by placing a pair

of points very close to the ends of the "straight" and "radii" sections and

two or three points in the short spline sections, but I always seem to get

wobbles in my curvature comb that I can't get rid of. Any rules of thumb on

how to place my spline points?

Should I worry about making the splines curvature smooth? Is this a

characteristic that the eye even notices?

Jerry Steiger

Tripod Data Systems

"take the garbage out, dear"