cur_approx - Geometric procedure

Creates a curve


Description

This procedure approximates a curve with another curve type.

The procedure can for instance be used to approximate a surface curve (a curve with UV_SEG segments) to a cubic curve (a curve with CUB_SEG segments).

Syntax

cur_approx(id, curve, ctype, method, cdata1, cdata2:attributes);

REF	id;
REF	curve;
STRING	ctype*7;
INT	method;
FLOAT	cdata1;
FLOAT	cdata2;

Principal parameters

id	- Local identity
curve	- Identity of curve
ctype	- Curve segment type
	"CUB_SEG" or "CUBIC" = Approximate with non rational cubic segments
	"RAT_SEG" or "RATIONAL" = Approximate with rational cubic segments
	"CIR_SEG" = Approximate with circular arcs and lines
method	- Approximation method
	1 = The number of segments is input (no tolerances used)
	2 = Reduce and/or add segments respecting the given tolerances
	(Implemented for ctype= CIR_SEG)
	3 = Add only segments respecting the given tolerances
cdata1	- Data 1 for the computation
	Requested number of segments for method= 1
	Coordinate tolerance for method= 2 and method=3

Optional parameters

cdata2	- Computational tolerance as follows:
	Tangent (angle) tolerence for method 2 and 3
	Criterion for a straight line (max curvature) for method 2 and ctype="CIR_SEG"

Attributes

PEN	- Pen or colour number
LEVEL	- Level number
BLANK	- Visible(0) or invisible(1)
WIDTH	- Linewidth
CFONT	- Solid (0), dashed (1) or centerline (2)
CDASHL	- Dash length

Example

cur_approx(#10, #5, "CUBIC", 1, 4);

Creates a new curve (#10) which approximates a previously created curve #5. The output curve will have cubic segments and the number of segments will be four times the number of segments for the old curve.
No tolerances are used in the calculations.