/**
* Attempts to return a rotation matrix corresponding to moving the plane between two cursor
* positions, with a given initial rotation matrix in effect.
*
* @param rot0 initial rotation matrix
* @param pos0 initial projected position
* @param pos1 destination projected position
* @return destination rotation matrix, or null
* @see Projection#projRotate
*/
private double[] genericRotate(double[] rot0, Point2D.Double pos0, Point2D.Double pos1) {
double[] rv0 = new double[3];
if (unproject(pos0, rv0)
&& getSkyviewProjecter().validPosition(new double[] {pos1.x, pos1.y})) {
double[] unrot0 = Matrices.invert(rot0);
double[] ru0 = Matrices.mvMult(unrot0, rv0);
return getRotation(ru0, pos1, rot0);
} else {
return null;
}
}
@Override
public double[] cursorRotate(double[] rot0, Point2D.Double pos0, Point2D.Double pos1) {
/* Attempt the rotation that transforms a point from one
* projected plane position to another. */
double[] rot1 = genericRotate(rot0, pos0, pos1);
if (rot1 != null) {
return rot1;
}
/* That may fail because one or other of the supplied points is
* not in the projection region. In that case do something
* that feels like dragging the sphere around.
* This rotation could be improved. It is algebraically messy,
* and it also does not transition smoothly from the genericRotate
* case, though perhaps that's not possible in general. */
else {
boolean reflect = isReflected(rot0);
double fr = reflect ? -1 : +1;
double phi = (pos1.x - pos0.x);
double psi = (pos1.y - pos0.y);
double[] rm = rot0;
double[] sightvec = Matrices.mvMult(Matrices.invert(rm), new double[] {1, 0, 0});
double[] hvec = Matrices.normalise(Matrices.cross(sightvec, RZ));
rm = rotateAround(rm, hvec, -psi);
rm = rotateAround(rm, RZ, -phi * fr);
if (Matrices.mvMult(rm, RZ)[2] >= 0) {
return rm;
} else {
double delta = Math.atan2(-rm[2], rm[8]);
double alpha = Math.atan2(-rm[3], rm[4] * fr);
delta = Math.min(+0.5 * Math.PI, delta);
delta = Math.max(-0.5 * Math.PI, delta);
return verticalRotate(delta, alpha, reflect);
}
}
}