VARKON Version 1.15 1997-10-24

getarc - Procedure

Get arc from GM


Description

Reads arc data from GM. In the case of a 3D arc getarc also returns 1, 2, 3 or 4 arc segments.

Syntax

getarc(id, font, dl, p, r, start, end, nseg, segdata)

REF	id;
INT	font;
FLOAT	dl;
VECTOR	p;
FLOAT	r;
FLOAT	start;
FLOAT	end;
INT	nseg;
FLOAT	segdata(4,4,4);

Principal parameters

id	- Global identity of an arc
font	- 0 = Solid, 1 = Dashed, 2 = Centerline
dl	- Dashlength if font = 1 or 2
p	- Coordinates of arc center
r	- Arc radius
start	- Start angle
end	- End angle
nseg	- Number of segments. For a 2D arc ns = 0.
segdata	- nseg 4 by 4 matrixes with polynomial segment coefficients

Optional parameters

None.

Comments

Each segment is a rational cubic with 0 to 1 parametrisation and the coefficients ordered as follows:

k0x k0y k0z k0w
k1x k1y k1z k1w
k2x k2y k2z k2w
k3x k3y k3z k3w

Se for example Faux and Pratt, "Computational Geometry for design and manufacture", page 144 for a further discussion on rational cubic parametric segments.