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/*
* Ken Shoemake's Quaternion rotation controller
*/
#include <u.h>
#include <libc.h>
#include <draw.h>
#include "dat.h"
#include "fns.h"
typedef struct Point2 Point2;
struct Point2 {
double x, y;
};
static Point2
Pt2(double x, double y)
{
return (Point2){x, y};
}
static Point2
addpt2(Point2 a, Point2 b)
{
return (Point2){a.x+b.x, a.y+b.y};
}
static Point2
subpt2(Point2 a, Point2 b)
{
return (Point2){a.x-b.x, a.y-b.y};
}
static Point2
divpt2(Point2 p, double s)
{
return (Point2){p.x/s, p.y/s};
}
/*
* Convert a mouse point into a unit quaternion, flattening if
* constrained to a particular plane.
*/
static Quaternion
mouseq(Point2 p, Quaternion *axis){
double l;
Quaternion q;
double rsq = p.x*p.x + p.y*p.y;
if(rsq > 1){
rsq = sqrt(rsq);
q.r = 0;
q.i = p.x/rsq;
q.j = p.y/rsq;
q.k = 0;
}else{
q.r = 0;
q.i = p.x;
q.j = p.y;
q.k = sqrt(1 - rsq);
}
if(axis != nil){
l = dotq(q, *axis);
q.i -= l*axis->i;
q.j -= l*axis->j;
q.k -= l*axis->k;
l = qlen(q);
if(l != 0){
q.i /= l;
q.j /= l;
q.k /= l;
}
}
return q;
}
void
qb(Rectangle r, Point p1, Point p2, Quaternion *orient, Quaternion *axis){
Quaternion q, down;
Point2 rmin, rmax;
Point2 ctlcen, ctlrad;
double qx, qy;
rmin = Pt2(r.min.x, r.min.y);
rmax = Pt2(r.max.x, r.max.y);
ctlcen = divpt2(addpt2(rmin, rmax), 2);
ctlrad = divpt2(subpt2(rmax, rmin), 2);
qx = (p1.x-ctlcen.x)/ctlrad.x;
qy = (ctlcen.y-p1.y)/ctlrad.y;
down = invq(mouseq(Pt2(qx, qy), axis));
q = *orient;
qx = (p2.x-ctlcen.x)/ctlrad.x;
qy = (ctlcen.y-p2.y)/ctlrad.y;
*orient = mulq(q, mulq(down, mouseq(Pt2(qx, qy), axis)));
}
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