/** @see <a href="gluUnProject.html">gluUnProject</a> */
public double[] un_project(
double window_x,
double window_y,
double window_z,
double[] modelview,
double[] projection,
int[] viewport) {
Matrix4d product = new Matrix4d();
Matrix4d.multiply(modelview, projection, product.m);
if (product.invert() == null) return null;
Vector4d A = new Vector4d(window_x, window_y, window_z, 1.0);
// map x and y from window coordinates
A.v[0] = (A.v[0] - viewport[0]) / viewport[2];
A.v[1] = (A.v[1] - viewport[1]) / viewport[3];
// map to range -1 to 1, A = 2*A - I
A.scalar_multiply(2).scalar_minus(1);
A.multiply_right(product);
double d = A.v[3];
if (d == 0) return null;
double[] result = new double[3]; // vs. 4
result[0] = A.v[0] / d;
result[1] = A.v[1] / d;
result[2] = A.v[2] / d;
return result;
}
/** @see <a href="gluLookAt.html">gluLookAt</a> */
public void look_at(
double eyex,
double eyey,
double eyez,
double centerx,
double centery,
double centerz,
double upx,
double upy,
double upz) {
Matrix4d matrix = new Matrix4d();
Vector4d eye = new Vector4d(eyex, eyey, eyez, 1.0);
Vector4d center = new Vector4d(centerx, centery, centerz, 1.0);
Vector4d up = new Vector4d(upx, upy, upz, 1.0);
Vector4d forward = new Vector4d();
Vector4d side = new Vector4d();
// -- make rotation matrix
// forward = center - eye
forward.minus(center, eye).normalize();
// side = (forward x up), then normalized
side.cross(forward, up).normalize();
// up = side x forward
up.cross(side, forward);
/* [side_x up_x -forward_x 0]
* [side_y up_y -forward_y 0]
* [side_z up_z -forward_z 0]
* [ 0 0 0 1]
*/
matrix.set_column(side, up, forward.negate(), Vector4d.ZERO);
matrix.set_row(3, 0.0, 0.0, 0.0, 1.0);
gl.mult_matrixd(matrix.m);
// -- translate eye to origin
gl.translated(-eyex, -eyey, -eyez);
}