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{alias:bsp}
h2. Name

*bsp* — B-spline visualization

h2. Syntax
{panel:|borderStyle=solid|borderWidth=1|bgColor=#FFFFAA}

*bsp* \[_size_] \[*q* | *cm* | *cm2*] \[*lin*] \[*sav* \[*nodraw*] ] \[*nst*] \[*col*]  ; # draw b-spline
{panel}

h2. 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. 

h2. Arguments

{indent}
No arguments. Draw cubic b-spline in *tube* mode through input points. 
{indent}
_size_ 
{indent}
Specify size of b-spline thickness either in tube or line mode. 
{indent}
*q* 
{indent}
Draw quadratic b-spline through input points. 
{indent}
*cm* 
{indent}
Draw cubic bspline and use the coeffisient matrix. 
{indent}
*cm2* 
{indent}
Draw quadratic bspline and use the coeffisient matrix. 
{indent}
*lin* 
{indent}
Draw in *line* mode (default is *tube*). 
{indent}
*sav* \[*nodraw*]
{indent}
Save the b-spline curve as a dataset in active. The \[*nodraw*] option prevents the spline to be drawn on the screen.
{indent}
*nst* _number_ 
{indent}
Number of steps between the knot points in the curve. 
{indent}
*col* 
{indent}
Color shift for each cell. 
{indent}

h2. Examples

h3. Ex.1: Drawing a b-spline curve

{noformat:|borderWidth=1|bgColor=#eeeeee}
        # 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
{noformat}

The above example produces this image. 

!att:_img_ref^cmd_bsp.png|border=1!
_B-spline curve with the control polygon_

h2. See also

[cur - Curve display], [spl - Spline generation], [pol - Polygon type display]
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