/* 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);
}
static HVect
V3_Unit (HVect v)
{
static HVect u = {0, 0, 0, 0};
double 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);
}
/* 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);
}
static HVect
ConstrainToAxis (HVect loose,
HVect axis)
{
HVect onPlane;
register double norm;
onPlane = V3_Sub(loose, V3_Scale(axis, V3_Dot(axis, loose)));
norm = V3_Norm(onPlane);
if (norm > 0.0)
{
if (onPlane.z < 0.0) onPlane = V3_Negate(onPlane);
return ( V3_Scale(onPlane, 1/sqrt(norm)) );
}
/* else drop through */
/* ================= */
if (axis.z == 1) onPlane = V3_(1.0, 0.0, 0.0);
else onPlane = V3_Unit(V3_(-axis.y, axis.x, 0.0));
return (onPlane);
}
