//Given a direction vector, get the rotation around the y axis
float GetYRotation(float fX, float fY, float fZ)
{
D3DVECTOR rlvPreDef, rlvDir;
D3DVALUE valCosTheta, fTheta;
// The pre-defined angle.
rlvPreDef.x = 0.0F;
rlvPreDef.y = 0.0F;
rlvPreDef.z = 1.0F;
// Make a D3DVECTOR from this vector.
rlvDir.x = fX;
rlvDir.y = fY;
rlvDir.z = fZ;
// First need angle between the pre-defined angle and rlvDir.
valCosTheta = D3DRMVectorDotProduct(&rlvPreDef, &rlvDir);
fTheta = (D3DVALUE)acos(valCosTheta);
// This will always be the acute angle. Since rotation will always be in positive direction we must
// give correct angle (possibly obtuse) for that direction.
if (rlvDir.x < 0.0F)
{
// Acute angle will not work, need obtuse angle.
fTheta = (2*PI) - fTheta;
}
return fTheta;
}
STDMETHODIMP CVectorObject::get_Rotation(float *pfTheta)
{
D3DVECTOR rlvPreDef, rlvDir;
D3DVALUE valCosTheta;
// The pre-defined angle.
rlvPreDef.x = 0.0F;
rlvPreDef.y = 0.0F;
rlvPreDef.z = 1.0F;
// Make a D3DVECTOR from this vector.
rlvDir.x = m_x;
rlvDir.y = m_y;
rlvDir.z = m_z;
D3DRMVectorNormalize(&rlvDir);
// First need angle between the pre-defined angle and rlvDir.
valCosTheta = D3DRMVectorDotProduct(&rlvPreDef, &rlvDir);
*pfTheta = (D3DVALUE)acos(valCosTheta);
// This will always be the acute angle. Since rotation will always be in positive direction we must
// give correct angle (possibly obtuse) for that direction.
if (rlvDir.x < 0.0F)
{
// Acute angle will not work, need obtuse angle.
*pfTheta = (2*PI) - *pfTheta;
}
return S_OK;
}
/* Interpolation between two quaternions */
LPD3DRMQUATERNION WINAPI D3DRMQuaternionSlerp(LPD3DRMQUATERNION q, LPD3DRMQUATERNION a, LPD3DRMQUATERNION b, D3DVALUE alpha)
{
D3DVALUE dot, epsilon, temp, theta, u;
D3DVECTOR v1, v2;
dot = a->s * b->s + D3DRMVectorDotProduct(&a->v, &b->v);
epsilon = 1.0f;
temp = 1.0f - alpha;
u = alpha;
if (dot < 0.0)
{
epsilon = -1.0;
dot = -dot;
}
if( 1.0f - dot > 0.001f )
{
theta = acos(dot);
temp = sin(theta * temp) / sin(theta);
u = sin(theta * alpha) / sin(theta);
}
q->s = temp * a->s + epsilon * u * b->s;
D3DRMVectorScale(&v1, &a->v, temp);
D3DRMVectorScale(&v2, &b->v, epsilon * u);
D3DRMVectorAdd(&q->v, &v1, &v2);
return q;
}
/* Reflection of a vector on a surface */
LPD3DVECTOR WINAPI D3DRMVectorReflect(LPD3DVECTOR r, LPD3DVECTOR ray, LPD3DVECTOR norm)
{
D3DVECTOR sca, temp;
D3DRMVectorSubtract(&temp, D3DRMVectorScale(&sca, norm, 2.0*D3DRMVectorDotProduct(ray,norm)), ray);
*r = temp;
return r;
}
/* Product of 2 quaternions */
LPD3DRMQUATERNION WINAPI D3DRMQuaternionMultiply(LPD3DRMQUATERNION q, LPD3DRMQUATERNION a, LPD3DRMQUATERNION b)
{
D3DRMQUATERNION temp;
D3DVECTOR cross_product;
D3DRMVectorCrossProduct(&cross_product, &a->v, &b->v);
temp.s = a->s * b->s - D3DRMVectorDotProduct(&a->v, &b->v);
temp.v.u1.x = a->s * b->v.u1.x + b->s * a->v.u1.x + cross_product.u1.x;
temp.v.u2.y = a->s * b->v.u2.y + b->s * a->v.u2.y + cross_product.u2.y;
temp.v.u3.z = a->s * b->v.u3.z + b->s * a->v.u3.z + cross_product.u3.z;
*q = temp;
return q;
}
