ballaux.c

[Game.Programming].Academic - Graphics Gems (6 books source code)

/***** BallAux.c *****/
#include <math.h>
#include "BallAux.h"

Quat qOne = {0, 0, 0, 1};

/* Return quaternion product qL * qR.  Note: order is important!
 * To combine rotations, use the product Mul(qSecond, qFirst),
 * which gives the effect of rotating by qFirst then qSecond. */
Quat Qt_Mul(Quat qL, Quat qR)
{
    Quat qq;
    qq.w = qL.w*qR.w - qL.x*qR.x - qL.y*qR.y - qL.z*qR.z;
    qq.x = qL.w*qR.x + qL.x*qR.w + qL.y*qR.z - qL.z*qR.y;
    qq.y = qL.w*qR.y + qL.y*qR.w + qL.z*qR.x - qL.x*qR.z;
    qq.z = qL.w*qR.z + qL.z*qR.w + qL.x*qR.y - qL.y*qR.x;
    return (qq);
}


/* Construct rotation matrix from (possibly non-unit) quaternion.
 * Assumes matrix is used to multiply column vector on the left:
 * vnew = mat vold.  Works correctly for right-handed coordinate system
 * and right-handed rotations. */
HMatrix *Qt_ToMatrix(Quat q, HMatrix out)
{
    double Nq = q.x*q.x + q.y*q.y + q.z*q.z + q.w*q.w;
    double s = (Nq > 0.0) ? (2.0 / Nq) : 0.0;
    double xs = q.x*s,	      ys = q.y*s,	  zs = q.z*s;
    double wx = q.w*xs,	      wy = q.w*ys,	  wz = q.w*zs;
    double xx = q.x*xs,	      xy = q.x*ys,	  xz = q.x*zs;
    double yy = q.y*ys,	      yz = q.y*zs,	  zz = q.z*zs;
    out[X][X] = 1.0 - (yy + zz); out[Y][X] = xy + wz; out[Z][X] = xz - wy;
    out[X][Y] = xy - wz; out[Y][Y] = 1.0 - (xx + zz); out[Z][Y] = yz + wx;
    out[X][Z] = xz + wy; out[Y][Z] = yz - wx; out[Z][Z] = 1.0 - (xx + yy);
    out[X][W] = out[Y][W] = out[Z][W] = out[W][X] = out[W][Y] = out[W][Z] = 0.0;
    out[W][W] = 1.0;
    return ((HMatrix *)&out);
}

/* Return conjugate of quaternion. */
Quat Qt_Conj(Quat q)
{
    Quat qq;
    qq.x = -q.x; qq.y = -q.y; qq.z = -q.z; qq.w = q.w;
    return (qq);
}

/* Return vector formed from components */
HVect V3_(float x, float y, float z)
{
    HVect v;
    v.x = x; v.y = y; v.z = z; v.w = 0;
    return (v);
}

/* Return norm of v, defined as sum of squares of components */
float V3_Norm(HVect v)
{
    return ( v.x*v.x + v.y*v.y + v.z*v.z );
}

/* Return unit magnitude vector in direction of v */
HVect V3_Unit(HVect v)
{
    static HVect u = {0, 0, 0, 0};
    float vlen = sqrt(V3_Norm(v));
    if (vlen != 0.0) {
	u.x = v.x/vlen; u.y = v.y/vlen; u.z = v.z/vlen;
    }
    return (u);
}

/* Return version of v scaled by s */
HVect V3_Scale(HVect v, float s)
{
    HVect u;
    u.x = s*v.x; u.y = s*v.y; u.z = s*v.z; u.w = v.w;
    return (u);
}

/* Return negative of v */
HVect V3_Negate(HVect v)
{
    static HVect u = {0, 0, 0, 0};
    u.x = -v.x; u.y = -v.y; u.z = -v.z;
    return (u);
}

/* Return sum of v1 and v2 */
HVect V3_Add(HVect v1, HVect v2)
{
    static HVect v = {0, 0, 0, 0};
    v.x = v1.x+v2.x; v.y = v1.y+v2.y; v.z = v1.z+v2.z;
    return (v);
}

/* Return difference of v1 minus v2 */
HVect V3_Sub(HVect v1, HVect v2)
{
    static HVect v = {0, 0, 0, 0};
    v.x = v1.x-v2.x; v.y = v1.y-v2.y; v.z = v1.z-v2.z;
    return (v);
}

/* Halve arc between unit vectors v0 and v1. */
HVect V3_Bisect(HVect v0, HVect v1)
{
    HVect v = {0, 0, 0, 0};
    float Nv;
    v = V3_Add(v0, v1);
    Nv = V3_Norm(v);
    if (Nv < 1.0e-5) {
	v = V3_(0, 0, 1);
    } else {
	v = V3_Scale(v, 1/sqrt(Nv));
    }
    return (v);
}

/* Return dot product of v1 and v2 */
float V3_Dot(HVect v1, HVect v2)
{
    return (v1.x*v2.x + v1.y*v2.y + v1.z*v2.z);
}


/* Return cross product, v1 x v2 */
HVect V3_Cross(HVect v1, HVect v2)
{
    static HVect v = {0, 0, 0, 0};
    v.x = v1.y*v2.z-v1.z*v2.y;
    v.y = v1.z*v2.x-v1.x*v2.z;
    v.z = v1.x*v2.y-v1.y*v2.x;
    return (v);
}