1 /*
2 * The following routines transform points and planes from one space
3 * to another. Points and planes are represented by their
4 * homogeneous coordinates, stored in variables of type Point3.
5 */
6 #include <u.h>
7 #include <libc.h>
8 #include <draw.h>
9 #include <geometry.h>
10 /*
11 * Transform point p.
12 */
xformpoint(Point3 p,Space * to,Space * from)13 Point3 xformpoint(Point3 p, Space *to, Space *from){
14 Point3 q, r;
15 register double *m;
16 if(from){
17 m=&from->t[0][0];
18 q.x=*m++*p.x; q.x+=*m++*p.y; q.x+=*m++*p.z; q.x+=*m++*p.w;
19 q.y=*m++*p.x; q.y+=*m++*p.y; q.y+=*m++*p.z; q.y+=*m++*p.w;
20 q.z=*m++*p.x; q.z+=*m++*p.y; q.z+=*m++*p.z; q.z+=*m++*p.w;
21 q.w=*m++*p.x; q.w+=*m++*p.y; q.w+=*m++*p.z; q.w+=*m *p.w;
22 }
23 else
24 q=p;
25 if(to){
26 m=&to->tinv[0][0];
27 r.x=*m++*q.x; r.x+=*m++*q.y; r.x+=*m++*q.z; r.x+=*m++*q.w;
28 r.y=*m++*q.x; r.y+=*m++*q.y; r.y+=*m++*q.z; r.y+=*m++*q.w;
29 r.z=*m++*q.x; r.z+=*m++*q.y; r.z+=*m++*q.z; r.z+=*m++*q.w;
30 r.w=*m++*q.x; r.w+=*m++*q.y; r.w+=*m++*q.z; r.w+=*m *q.w;
31 }
32 else
33 r=q;
34 return r;
35 }
36 /*
37 * Transform point p with perspective division.
38 */
xformpointd(Point3 p,Space * to,Space * from)39 Point3 xformpointd(Point3 p, Space *to, Space *from){
40 p=xformpoint(p, to, from);
41 if(p.w!=0){
42 p.x/=p.w;
43 p.y/=p.w;
44 p.z/=p.w;
45 p.w=1;
46 }
47 return p;
48 }
49 /*
50 * Transform plane p -- same as xformpoint, except multiply on the
51 * other side by the inverse matrix.
52 */
xformplane(Point3 p,Space * to,Space * from)53 Point3 xformplane(Point3 p, Space *to, Space *from){
54 Point3 q, r;
55 register double *m;
56 if(from){
57 m=&from->tinv[0][0];
58 q.x =*m++*p.x; q.y =*m++*p.x; q.z =*m++*p.x; q.w =*m++*p.x;
59 q.x+=*m++*p.y; q.y+=*m++*p.y; q.z+=*m++*p.y; q.w+=*m++*p.y;
60 q.x+=*m++*p.z; q.y+=*m++*p.z; q.z+=*m++*p.z; q.w+=*m++*p.z;
61 q.x+=*m++*p.w; q.y+=*m++*p.w; q.z+=*m++*p.w; q.w+=*m *p.w;
62 }
63 else
64 q=p;
65 if(to){
66 m=&to->t[0][0];
67 r.x =*m++*q.x; r.y =*m++*q.x; r.z =*m++*q.x; r.w =*m++*q.x;
68 r.x+=*m++*q.y; r.y+=*m++*q.y; r.z+=*m++*q.y; r.w+=*m++*q.y;
69 r.x+=*m++*q.z; r.y+=*m++*q.z; r.z+=*m++*q.z; r.w+=*m++*q.z;
70 r.x+=*m++*q.w; r.y+=*m++*q.w; r.z+=*m++*q.w; r.w+=*m *q.w;
71 }
72 else
73 r=q;
74 return r;
75 }
76