bsp - B spline visualization

Name

bsp — B-spline visualization

Syntax

bsp [size] [q | cm | cm2] [lin] [sav [nodraw] ] [nst] [col] ; # draw b-spline

Description

Draw a b-spline curve close to the points in active workspace. The curve will not interpolate the input points, but follows the control polygon that goes between the input points which are the knot points in the curve.

Arguments

No arguments. Draw cubic b-spline in tube mode through input points.

size

Specify size of b-spline thickness either in tube or line mode.

q

Draw quadratic b-spline through input points.

cm

Draw cubic bspline and use the coeffisient matrix.

cm2

Draw quadratic bspline and use the coeffisient matrix.

lin

Draw in line mode (default is tube).

sav [nodraw]

Save the b-spline curve as a dataset in active. The nodraw option prevents the spline to be drawn on the screen.

nst number

Number of steps between the knot points in the curve.

col

Color shift for each cell.

Examples

Ex.1: Drawing a b-spline curve

        # Digitize points and draw a b-spline
        rcd  ;#  digitize 5 points
        u    ;#  stop digitizing
        poi  ;#  display points
        pol  ;#  display line polygons
        bsp  ;#   draw a b-spline

The above example produces this image.

B-spline curve with the control polygon