/**
* <code>toRotationMatrix</code> converts this quaternion to a rotational matrix. The result is
* stored in result. 4th row and 4th column values are untouched. Note: the result is created from
* a normalized version of this quat.
*
* @param result The Matrix4f to store the result in.
* @return the rotation matrix representation of this quaternion.
*/
public Matrix4f toRotationMatrix(Matrix4f result) {
float norm = norm();
// we explicitly test norm against one here, saving a division
// at the cost of a test and branch. Is it worth it?
float s = (norm == 1f) ? 2f : (norm > 0f) ? 2f / norm : 0;
// compute xs/ys/zs first to save 6 multiplications, since xs/ys/zs
// will be used 2-4 times each.
float xs = x * s;
float ys = y * s;
float zs = z * s;
float xx = x * xs;
float xy = x * ys;
float xz = x * zs;
float xw = w * xs;
float yy = y * ys;
float yz = y * zs;
float yw = w * ys;
float zz = z * zs;
float zw = w * zs;
// using s=2/norm (instead of 1/norm) saves 9 multiplications by 2 here
result.m00 = 1 - (yy + zz);
result.m01 = (xy - zw);
result.m02 = (xz + yw);
result.m10 = (xy + zw);
result.m11 = 1 - (xx + zz);
result.m12 = (yz - xw);
result.m20 = (xz - yw);
result.m21 = (yz + xw);
result.m22 = 1 - (xx + yy);
return result;
}
