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// LookAt matrix code (may be implemented into libpsxgte soon)
#include "lookat.h"
void crossProduct(SVECTOR *v0, SVECTOR *v1, VECTOR *out) {
out->vx = ((v0->vy*v1->vz)-(v0->vz*v1->vy))>>12;
out->vy = ((v0->vz*v1->vx)-(v0->vx*v1->vz))>>12;
out->vz = ((v0->vx*v1->vy)-(v0->vy*v1->vx))>>12;
}
void LookAt(VECTOR *eye, VECTOR *at, SVECTOR *up, MATRIX *mtx) {
VECTOR taxis;
SVECTOR zaxis;
SVECTOR xaxis;
SVECTOR yaxis;
VECTOR pos;
VECTOR vec;
setVector(&taxis, at->vx-eye->vx, at->vy-eye->vy, at->vz-eye->vz);
VectorNormalS(&taxis, &zaxis);
crossProduct(&zaxis, up, &taxis);
VectorNormalS(&taxis, &xaxis);
crossProduct(&zaxis, &xaxis, &taxis);
VectorNormalS(&taxis, &yaxis);
mtx->m[0][0] = xaxis.vx; mtx->m[1][0] = yaxis.vx; mtx->m[2][0] = zaxis.vx;
mtx->m[0][1] = xaxis.vy; mtx->m[1][1] = yaxis.vy; mtx->m[2][1] = zaxis.vy;
mtx->m[0][2] = xaxis.vz; mtx->m[1][2] = yaxis.vz; mtx->m[2][2] = zaxis.vz;
pos.vx = -eye->vx;;
pos.vy = -eye->vy;;
pos.vz = -eye->vz;;
ApplyMatrixLV(mtx, &pos, &vec);
TransMatrix(mtx, &vec);
}
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