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/*
* pvector.c - useful vector operations - these actually are on coords
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include "CNdata.h"
#include "CNpvector.h"
/*
* Normalize a vector
* return 0 if the vector has zero-length
*/
int CNnormalize_vector(va)
CNcoord *va;
{
double dx,dy,dz,ds=1.0;
/* Get the vector length */
dx = va->x;
dy = va->y;
dz = va->z;
ds = sqrt(dx*dx + dy*dy + dz*dz);
if (ds < CN_SMALLER) return(0);
/* Now normalize */
va->x = va->x/ds;
va->y = va->y/ds;
va->z = va->z/ds;
/* Return status */
return(1);
}
/*
* Return the length-squared of a vector
*/
double CNvector_lengthsq(va)
CNcoord *va;
{
double ds;
/* Get the vector length */
ds = va->x*va->x + va->y*va->y + va->z*va->z;
/* Return */
return(ds);
}
/*
* Get the angle between 2 vectors
*/
double CNvector_angle(A,B)
CNcoord *A, *B;
{
double dotprod, angle;
CNcoord va, vb;
/* Make copies of the vectors */
va.x = A->x;
va.y = A->y;
va.z = A->z;
vb.x = B->x;
vb.y = B->y;
vb.z = B->z;
/* Normalize the vectors first */
(void) CNnormalize_vector(&va);
(void) CNnormalize_vector(&vb);
dotprod = CNvector_dotproduct(&va,&vb);
angle = acos(dotprod);
return(angle);
}
/*
* Get the dot product of 2 vectors
*/
double CNvector_dotproduct(A,B)
CNcoord *A, *B;
{
double res;
res = A->x * B->x + A->y * B->y + A->z * B->z;
return(res);
}
/*
* find the normal vector of a plane
* This gets 3 points and returns a,b,c,d of the plane
*/
void CNconv_tria_to_plane(x1,y1,z1,x2,y2,z2,x3,y3,z3,a,b,c,d)
double x1,y1,z1,x2,y2,z2,x3,y3,z3;
double *a,*b,*c,*d;
{
CNcoord p1, p2, p3;
CNcoord normal;
double a0,b0,c0,d0;
/* Put the points into point data-structure */
p1.x = x1; p1.y = y1; p1.z = z1;
p2.x = x2; p2.y = y2; p2.z = z2;
p3.x = x3; p3.y = y3; p3.z = z3;
/* Get the plane-normal */
CNfind_normal_vector(&p1,&p2,&p3,&normal);
/* The plane equation is ax+by+cz+d = 0 */
a0 = normal.x;
b0 = normal.y;
c0 = normal.z;
d0 = -1.0*(a0*x1 + b0*y1 + c0*z1);
/* Normalize the plane */
if (fabs(a0) > CN_SMALLER) {
*a = a0 / a0;
*b = b0 / a0;
*c = c0 / a0;
*d = d0 / a0;
} else if (fabs(b0) > CN_SMALLER) {
*a = a0 / b0;
*b = b0 / b0;
*c = c0 / b0;
*d = d0 / b0;
} else if (fabs(c0) > CN_SMALLER) {
*a = a0 / c0;
*b = b0 / c0;
*c = c0 / c0;
*d = d0 / c0;
} else {
*a = a0;
*b = b0;
*c = c0;
*d = d0;
}
}
/*
* find the normal vector of a plane
*/
void CNfind_normal_vector(pa1,pa2,pa3,normal)
CNcoord *pa1,*pa2,*pa3,*normal;
{
CNcoord lv1, lv2;
lv1 = CNfind_line_vector(pa1,pa2);
lv2 = CNfind_line_vector(pa2,pa3);
*normal = CNcross_product(&lv1,&lv2);
}
/*
* given 2 points, find the line vector
*/
CNcoord CNfind_line_vector(p1,p2)
CNcoord *p1, *p2;
{
CNcoord linevec;
linevec.x = p2->x - p1->x;
linevec.y = p2->y - p1->y;
linevec.z = p2->z - p1->z;
return(linevec);
}
/*
* find the cross product of 2 vectors
*/
CNcoord CNcross_product(vec1,vec2)
CNcoord *vec1, *vec2;
{
CNcoord cross;
/* A x B = (AyBz - AzBy)x + (AzBx - AxBz)y + (AxBy - AyBx)z */
cross.x = vec1->y * vec2->z - vec1->z * vec2->y;
cross.y = vec1->z * vec2->x - vec1->x * vec2->z;
cross.z = vec1->x * vec2->y - vec1->y * vec2->x;
return(cross);
}
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