Function:ns2varc
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| ==Description== | ==Description== | ||
| - | + | Draw an arc centered around position P with surface normal N using the current pen thickness and colour. Vector S gives the position (both direction and radius) relative to P, from which the first segment of the arc is drawn. 'deg' specifies the arc angle in degrees, which is broken into 'nseg' segments. | |
| - | Draw an arc at position P with normal N using the current pen thickness and colour. Vector S gives starting vector from P and is rotated around the normal in steps (deg/(nseg-1)). | + | |
| This function is an "extension", and its behaviour for world coordinates which have unequal scales in x, y and/or z is not particularly well defined. | This function is an "extension", and its behaviour for world coordinates which have unequal scales in x, y and/or z is not particularly well defined. | ||
| + | |||
| + | If the surface normal N is calculated using a vector cross-product, for the purpose of drawing an arc between two given vectors, the first vector parameter in the cross-product calculation should be used as the reference direction for S. | ||
| == See Also == | == See Also == | ||
Current revision
ns2varc
Draw an arc at (px,py,pz) with normal (nx,ny,nz) in current pen (thickness,colour) - vector input.
Prototype
void ns2varc(XYZ P, XYZ N, XYZ S, float deg, int nseg);
Description
Draw an arc centered around position P with surface normal N using the current pen thickness and colour. Vector S gives the position (both direction and radius) relative to P, from which the first segment of the arc is drawn. 'deg' specifies the arc angle in degrees, which is broken into 'nseg' segments.
This function is an "extension", and its behaviour for world coordinates which have unequal scales in x, y and/or z is not particularly well defined.
If the surface normal N is calculated using a vector cross-product, for the purpose of drawing an arc between two given vectors, the first vector parameter in the cross-product calculation should be used as the reference direction for S.
See Also
Code Example
#include <stdio.h>
#include <stdlib.h>
#include "s2plot.h"
int main(int argc, char *argv[])
{
XYZ pos; /* Position */
XYZ normal; /* Normal */
XYZ start; /* Starting vector */
float deg = 180.0; /* Angular extent */
int nseg = 48; /* Number of segments */
s2opend("/?",argc, argv); /* Open the display */
s2swin(-1.,1., -1.,1., -1.,1.); /* Set the window coordinates */
s2box("BCDET",0,0,"BCDET",0,0,"BCDET",0,0); /* Draw coordinate box */
pos.x = 0.0; pos.y = 0.0; pos.z = 0.0; /* Set position */
normal.x = 0.0; normal.y = 1.0; normal.z = 1.0; /* Normal vector */
start.x = 1.0; start.y = 0.0; start.z = 0.0; /* Normal vector */
s2slw(3); /* Set line width */
s2sci(S2_PG_YELLOW); /* Set the colour */
ns2varc(pos, normal, start, deg, nseg); /* Draw the arc */
s2show(1); /* Open the s2plot window */
return 1;
}
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