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/*
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* The following routines transform points and planes from one space
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* to another. Points and planes are represented by their
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* homogeneous coordinates, stored in variables of type Point3.
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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 <geometry.h>
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/*
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* Transform point p.
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*/
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Point3 xformpoint(Point3 p, Space *to, Space *from){
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Point3 q, r;
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register double *m;
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if(from){
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m=&from->t[0][0];
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q.x=*m++*p.x; q.x+=*m++*p.y; q.x+=*m++*p.z; q.x+=*m++*p.w;
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q.y=*m++*p.x; q.y+=*m++*p.y; q.y+=*m++*p.z; q.y+=*m++*p.w;
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q.z=*m++*p.x; q.z+=*m++*p.y; q.z+=*m++*p.z; q.z+=*m++*p.w;
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q.w=*m++*p.x; q.w+=*m++*p.y; q.w+=*m++*p.z; q.w+=*m *p.w;
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}
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else
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q=p;
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if(to){
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m=&to->tinv[0][0];
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r.x=*m++*q.x; r.x+=*m++*q.y; r.x+=*m++*q.z; r.x+=*m++*q.w;
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r.y=*m++*q.x; r.y+=*m++*q.y; r.y+=*m++*q.z; r.y+=*m++*q.w;
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r.z=*m++*q.x; r.z+=*m++*q.y; r.z+=*m++*q.z; r.z+=*m++*q.w;
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r.w=*m++*q.x; r.w+=*m++*q.y; r.w+=*m++*q.z; r.w+=*m *q.w;
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}
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else
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r=q;
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return r;
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}
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/*
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* Transform point p with perspective division.
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*/
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Point3 xformpointd(Point3 p, Space *to, Space *from){
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p=xformpoint(p, to, from);
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if(p.w!=0){
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p.x/=p.w;
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p.y/=p.w;
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p.z/=p.w;
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p.w=1;
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}
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return p;
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}
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/*
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* Transform plane p -- same as xformpoint, except multiply on the
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* other side by the inverse matrix.
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*/
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Point3 xformplane(Point3 p, Space *to, Space *from){
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Point3 q, r;
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register double *m;
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if(from){
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m=&from->tinv[0][0];
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q.x =*m++*p.x; q.y =*m++*p.x; q.z =*m++*p.x; q.w =*m++*p.x;
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q.x+=*m++*p.y; q.y+=*m++*p.y; q.z+=*m++*p.y; q.w+=*m++*p.y;
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q.x+=*m++*p.z; q.y+=*m++*p.z; q.z+=*m++*p.z; q.w+=*m++*p.z;
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q.x+=*m++*p.w; q.y+=*m++*p.w; q.z+=*m++*p.w; q.w+=*m *p.w;
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}
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else
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q=p;
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if(to){
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m=&to->t[0][0];
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r.x =*m++*q.x; r.y =*m++*q.x; r.z =*m++*q.x; r.w =*m++*q.x;
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r.x+=*m++*q.y; r.y+=*m++*q.y; r.z+=*m++*q.y; r.w+=*m++*q.y;
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r.x+=*m++*q.z; r.y+=*m++*q.z; r.z+=*m++*q.z; r.w+=*m++*q.z;
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r.x+=*m++*q.w; r.y+=*m++*q.w; r.z+=*m++*q.w; r.w+=*m *q.w;
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}
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else
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r=q;
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return r;
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}
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