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/* name: geom3d.c */
/* author: J. Michael Word date written: 2/9/96 */
/* purpose: collection of geometric primatives */
/* from Graphics Gems book. */
/*****************************************************************/
/* NOTICE: This is free software and the source code is freely */
/* available. You are free to redistribute or modify under the */
/* conditions that (1) this notice is not removed or modified */
/* in any way and (2) any modified versions of the program are */
/* also available for free. */
/* ** Absolutely no Warranty ** */
/* Copyright (C) 1999 J. Michael Word */
/*****************************************************************/
#include <math.h>
#include "geom3d.h"
double v3squaredLength(vector3d* a) {
return ((a->x * a->x)+(a->y * a->y)+(a->z * a->z));
}
double v3length(vector3d* a) {
return(sqrt(v3squaredLength(a)));
}
vector3d* v3negate(vector3d* v) {
v->x = -v->x; v->y = -v->y; v->z = -v->z;
return(v);
}
vector3d* v3normalize(vector3d* v) {
double len = v3length(v);
if (len != 0.0) { v->x /= len; v->y /= len; v->z /= len; }
return(v);
}
vector3d* v3scale(vector3d* v, double newlen) {
double len = v3length(v), scale;
if (len != 0.0) {
scale = newlen/len;
v->x *= scale; v->y *= scale; v->z *= scale;
}
return(v);
}
vector3d* v3add(vector3d* a, vector3d* b, vector3d* c) {
c->x = a->x+b->x; c->y = a->y+b->y; c->z = a->z+b->z;
return(c);
}
vector3d* v3sub(vector3d* a, vector3d* b, vector3d* c) {
c->x = a->x-b->x; c->y = a->y-b->y; c->z = a->z-b->z;
return(c);
}
double v3dot(vector3d* a, vector3d* b) {
return((a->x*b->x) + (a->y*b->y) + (a->z*b->z));
}
vector3d* v3lerp(vector3d* lo, vector3d* hi, double alpha, vector3d* rslt) {
rslt->x = LERP(alpha, lo->x, hi->x);
rslt->y = LERP(alpha, lo->y, hi->y);
rslt->z = LERP(alpha, lo->z, hi->z);
return(rslt);
}
vector3d* v3cross(vector3d* a, vector3d* b, vector3d* c) {
c->x = (a->y*b->z) - (a->z*b->y);
c->y = (a->z*b->x) - (a->x*b->z);
c->z = (a->x*b->y) - (a->y*b->x);
return(c);
}
double v3distanceSq(point3d* a, point3d* b) {
double dx = a->x-b->x;
double dy = a->y-b->y;
double dz = a->z-b->z;
return((dx*dx)+(dy*dy)+(dz*dz));
}
double v3distance(point3d* a, point3d* b) {
return(sqrt(v3distanceSq(a, b)));
}
vector3d* v3makeVec(point3d* a, point3d* b, vector3d* v) {
v->x = a->x - b->x;
v->y = a->y - b->y;
v->z = a->z - b->z;
return(v3normalize(v));
}
matrix4* v3identityMat(matrix4* m) {
m->element[0][0] = 1.0;
m->element[0][1] = 0.0;
m->element[0][2] = 0.0;
m->element[0][3] = 0.0;
m->element[1][0] = 0.0;
m->element[1][1] = 1.0;
m->element[1][2] = 0.0;
m->element[1][3] = 0.0;
m->element[2][0] = 0.0;
m->element[2][1] = 0.0;
m->element[2][2] = 1.0;
m->element[2][3] = 0.0;
m->element[3][0] = 0.0;
m->element[3][1] = 0.0;
m->element[3][2] = 0.0;
m->element[3][3] = 1.0;
return(m);
}
point3d* v3mulPointMat(point3d* p, matrix4* m) {
double x, y, z, w;
x = (p->x * m->element[0][0]) +
(p->y * m->element[1][0]) +
(p->z * m->element[2][0]) +
m->element[3][0];
y = (p->x * m->element[0][1]) +
(p->y * m->element[1][1]) +
(p->z * m->element[2][1]) +
m->element[3][1];
z = (p->x * m->element[0][2]) +
(p->y * m->element[1][2]) +
(p->z * m->element[2][2]) +
m->element[3][2];
w = (p->x * m->element[0][3]) +
(p->y * m->element[1][3]) +
(p->z * m->element[2][3]) +
m->element[3][3];
p->x = x;
p->y = y;
p->z = z;
if (w != 0.0) { p->x /= w; p->y /= w; p->z /= w; }
return(p);
}
matrix4* v3matMul(matrix4* a, matrix4* b, matrix4* c) {
int i, j, k;
for (i=0; i < 4; i++) {
for (j=0; j < 4; j++) {
c->element[i][j] = 0.0;
for (k=0; k < 4; k++) {
c->element[i][j] +=
a->element[i][k] * b->element[k][j];
}
}
}
return(c);
}
/* v3rotationMat() - build a rotation matrix */
matrix4* v3rotationMat(vector3d* axis, double theta, matrix4* m) {
double c, s, t, x, y, z;
x = axis->x;
y = axis->y;
z = axis->z;
c = cos(theta*DEG2RAD);
s = sin(theta*DEG2RAD);
t = 1.0 - c;
v3identityMat(m);
m->element[0][0] = t * x * x + c;
m->element[0][1] = t * x * y + z * s;
m->element[0][2] = t * x * z - y * s;
m->element[1][0] = t * y * x - z * s;
m->element[1][1] = t * y * y + c;
m->element[1][2] = t * y * z + x * s;
m->element[2][0] = t * z * x + y * s;
m->element[2][1] = t * z * y - x * s;
m->element[2][2] = t * z * z + c;
return(m);
}
/* v3translationMat() - build a translation matrix */
matrix4* v3translationMat(vector3d* axis, matrix4* m) {
v3identityMat(m);
m->element[3][0] = axis->x;
m->element[3][1] = axis->y;
m->element[3][2] = axis->z;
return(m);
}
/* v3rotate() - rotate p around the a->b axis */
point3d* v3rotate(point3d* p, double theta, point3d* a, point3d* b) {
vector3d axis;
point3d q;
matrix4 rotmat;
v3makeVec(b, a, &axis);
v3rotationMat(&axis, theta, &rotmat);
v3sub(p, b, &q);
v3mulPointMat(&q, &rotmat);
v3add(&q, b, p);
return(p);
}
/* v3angle() - calculate the angle (radians) between 3 points */
double v3angle(point3d* p1, point3d* p2, point3d* p3) {
vector3d a, b;
double amag, bmag, dotval, theta;
dotval = v3dot(v3sub(p1, p2, &a), v3sub(p3, p2, &b));
amag = v3length(&a);
bmag = v3length(&b);
if (amag*bmag < 0.0001) { theta = 0.0; }
else { theta = acos(dotval/(amag*bmag)); }
return(theta);
}
/* v3dihedral() - calculate the dihedral angle (radians) given 4 points */
double v3dihedral(point3d* p1, point3d* p2, point3d* p3, point3d* p4) {
vector3d a, b, c, d, e, f;
double dmag, emag, fmag, theta, phi;
v3cross(v3sub(p1, p2, &a), v3sub(p3, p2, &b), &d);
v3cross(v3sub(p2, p3, &b), v3sub(p4, p3, &c), &e);
dmag = v3length(&d);
emag = v3length(&e);
if (dmag*emag < 0.0001) { theta = 0.0; }
else { theta = acos(v3dot(&d, &e)/(dmag*emag)); }
v3cross(&d, &b, &f); /* this part sets the correct handedness */
fmag = v3length(&f);
if (fmag*emag < 0.0001) { phi = 0.0; }
else { phi = acos(v3dot(&f, &e)/(fmag*emag)); }
if (phi*RAD2DEG > 90.0) { theta = - theta; };
return(theta);
}
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