1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
|
/*
* Ken Shoemake's Quaternion rotation controller
* “Arcball Rotation Control”, Graphics Gems IV § III.1, pp. 175-192, August 1994.
*/
#include <u.h>
#include <libc.h>
#include <bio.h>
#include <thread.h>
#include <draw.h>
#include <memdraw.h>
#include <mouse.h>
#include <keyboard.h>
#include <geometry.h>
#include "libobj/obj.h"
#include "libgraphics/graphics.h"
#include "fns.h"
#define MIN(a, b) ((a)<(b)?(a):(b))
/*
* 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; /* quadrance */
q.r = 0;
if(rsq > 1){ /* outside the sphere */
rsq = 1/sqrt(rsq);
q.i = p.x*rsq;
q.j = p.y*rsq;
q.k = 0;
}else{
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
qball(Rectangle r, Point p0, Point p1, Quaternion *orient, Quaternion *axis)
{
Quaternion qdown, qdrag;
Point2 rmin, rmax;
Point2 v0, v1; /* unit sphere coords */
Point2 ctlcen; /* controller center */
double ctlrad; /* controller radius */
if(orient == nil)
return;
rmin = Vec2(r.min.x, r.min.y);
rmax = Vec2(r.max.x, r.max.y);
ctlcen = divpt2(addpt2(rmin, rmax), 2);
ctlrad = MIN(Dx(r)/2, Dy(r)/2);
v0 = divpt2(Vec2(p0.x-ctlcen.x, ctlcen.y-p0.y), ctlrad);
v1 = divpt2(Vec2(p1.x-ctlcen.x, ctlcen.y-p1.y), ctlrad);
qdown = mouseq(v0, axis);
qdrag = mulq(mouseq(v1, axis), qdown);
*orient = mulq(qdrag, *orient);
}
|
