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WebSVN – planix.SVN – Blame – /os/branches/feature_fixcpp/sys/src/libgeometry/qball.c – Rev 2

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/*
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 * Ken Shoemake's Quaternion rotation controller
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 */
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#include <u.h>
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#include <libc.h>
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#include <draw.h>
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#include <event.h>
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#include <geometry.h>
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#define	BORDER	4
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static Point ctlcen;		/* center of qball */
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static int ctlrad;		/* radius of qball */
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static Quaternion *axis;	/* constraint plane orientation, 0 if none */
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/*
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 * Convert a mouse point into a unit quaternion, flattening if
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 * constrained to a particular plane.
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 */
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static Quaternion mouseq(Point p){
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	double qx=(double)(p.x-ctlcen.x)/ctlrad;
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	double qy=(double)(p.y-ctlcen.y)/ctlrad;
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	double rsq=qx*qx+qy*qy;
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	double l;
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	Quaternion q;
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	if(rsq>1){
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		rsq=sqrt(rsq);
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		q.r=0.;
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		q.i=qx/rsq;
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		q.j=qy/rsq;
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		q.k=0.;
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	}
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	else{
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		q.r=0.;
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		q.i=qx;
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		q.j=qy;
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		q.k=sqrt(1.-rsq);
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	}
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	if(axis){
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		l=q.i*axis->i+q.j*axis->j+q.k*axis->k;
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		q.i-=l*axis->i;
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		q.j-=l*axis->j;
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		q.k-=l*axis->k;
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		l=sqrt(q.i*q.i+q.j*q.j+q.k*q.k);
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		if(l!=0.){
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			q.i/=l;
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			q.j/=l;
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			q.k/=l;
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		}
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	}
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	return q;
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}
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void qball(Rectangle r, Mouse *m, Quaternion *result, void (*redraw)(void), Quaternion *ap){
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	Quaternion q, down;
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	Point rad;
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	axis=ap;
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	ctlcen=divpt(addpt(r.min, r.max), 2);
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	rad=divpt(subpt(r.max, r.min), 2);
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	ctlrad=(rad.x<rad.y?rad.x:rad.y)-BORDER;
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	down=qinv(mouseq(m->xy));
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	q=*result;
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	for(;;){
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		*m=emouse();
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		if(!m->buttons) break;
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		*result=qmul(q, qmul(down, mouseq(m->xy)));
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		(*redraw)();
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	}
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}