public RotationQuaternion(Vector3D axis, double angle)
{
double sinCoeff = Math.Sin(angle / 2);
this._r = Math.Cos(angle / 2);
this._v = new Vector3D( axis.x() * sinCoeff,
axis.y() * sinCoeff,
axis.z() * sinCoeff);
}
private PixelInformation getIlluminationDirectionPerRenderingPixel(SpacecraftState sc, uint x, uint y)
{
PixelInformation PixelOut = new PixelInformation();
Vector3D c_pos = sc.getPosition();
// STEP 1: Visibility Test
Vector3D rayDirection = (sc.getPOVDirection() + (((1 + Convert.ToDouble(this._height) - (2 * Convert.ToDouble(y))) / (2 * Convert.ToDouble(this._height))) * sc.getPOVUp()) - (((1 + Convert.ToDouble(this._width) - (2 * Convert.ToDouble(x))) / (2 * Convert.ToDouble(this._width))) * sc.getPOVRight())).unit();
double discriminant = 4 * Math.Pow(c_pos * rayDirection, 2) - 4 * (rayDirection * rayDirection) * (c_pos * c_pos) + 4 * (rayDirection * rayDirection) * Math.Pow(_moon_radius, 2);
bool encounter = false;
Vector3D p_surf = new Vector3D();
if (discriminant < 0)
{
// no encounter
}
else if (discriminant == 0)
{
// one intersection
encounter = true;
double t = (-2 * (c_pos * rayDirection)) / (2 * (rayDirection * rayDirection));
p_surf = c_pos + rayDirection * t;
}
else
{
// two intersections
encounter = true;
double t1 = (-2 * (c_pos * rayDirection) + Math.Sqrt(discriminant)) / (2 * (rayDirection * rayDirection));
double t2 = (-2 * (c_pos * rayDirection) - Math.Sqrt(discriminant)) / (2 * (rayDirection * rayDirection));
Vector3D ray_point1 = c_pos + rayDirection * t1;
Vector3D ray_point2 = c_pos + rayDirection * t2;
double ray_norm1 = (ray_point1 - c_pos).norm();
double ray_norm2 = (ray_point2 - c_pos).norm();
if (ray_norm1 < ray_norm2)
{
p_surf = ray_point1;
}
else
{
p_surf = ray_point2;
}
}
if (encounter)
{
/*
Pixel shows the Moon's surface: Continue with executing steps 2 - 8.
*/
double x1 = Convert.ToDouble(x);
double y1 = Convert.ToDouble(y);
// STEP 2: Obtaining the Surface Hit Point
PixelOut.lat = tools.rad2deg((Math.PI / 2) - Math.Acos(p_surf.z() / _moon_radius));
PixelOut.lon = tools.rad2deg(Math.Atan2(p_surf.y(), p_surf.x()));
// STEP 3: Calculation of the Sun's direction
Vector3D hat_p_surf = p_surf.unit();
Vector3D hat_d_sun = (sc.getSunPosition() - p_surf).unit();
// STEP 4: Derivation of the Local Tangent Plane of the Surface Hit Point (nothing to do here)
// STEP 5: Determination of a Subsurface Point of the Solar Illumination Direction on the Local Tangent Plane
double lambda_5 = -(1000 * (hat_d_sun.x() * hat_p_surf.x() + hat_d_sun.y() * hat_p_surf.y() + hat_d_sun.z() * hat_p_surf.z())) / (hat_p_surf.x() * hat_p_surf.x() + hat_p_surf.y() * hat_p_surf.y() + hat_p_surf.z() * hat_p_surf.z());
Vector3D p_local = p_surf + 1000 * hat_d_sun + lambda_5 * hat_p_surf;
// STEP 6: Local Illumination Direction
Vector3D hat_d_local = (p_local - c_pos).unit();
/// STEP 7: Projection of the Local Illumination Point to the Image Plane
Vector3D k = c_pos + sc.getPOVDirection();
Vector3D c_up = sc.getPOVUp();
Vector3D c_right = sc.getPOVRight();
double w = Convert.ToDouble(this._width);
double h = Convert.ToDouble(this._height);
double x2 =
(
-2 * w * c_pos.y() * c_up.z() * hat_d_local.x() - c_right.y() * c_up.z() * hat_d_local.x() - w * c_right.y() * c_up.z() * hat_d_local.x()
+ 2 * w * c_pos.x() * c_up.z() * hat_d_local.y() + c_right.x() * c_up.z() * hat_d_local.y() + w * c_right.x() * c_up.z() * hat_d_local.y()
+ 2 * w * c_pos.z() * (c_up.y() * hat_d_local.x() - c_up.x() * hat_d_local.y())
+ (1 + w) * c_right.z() * (c_up.y() * hat_d_local.x() - c_up.x() * hat_d_local.y())
+ 2 * w * c_pos.y() * c_up.x() * hat_d_local.z() + c_right.y() * c_up.x() * hat_d_local.z() + w * c_right.y() * c_up.x() * hat_d_local.z()
- 2 * w * c_pos.x() * c_up.y() * hat_d_local.z() - c_right.x() * c_up.y() * hat_d_local.z() - w * c_right.x() * c_up.y() * hat_d_local.z()
- 2 * w * c_up.z() * hat_d_local.y() * k.x() + 2 * w * c_up.y() * hat_d_local.z() * k.x() + 2 * w * c_up.z() * hat_d_local.x() * k.y() - 2 * w * c_up.x() * hat_d_local.z() * k.y()
- 2 * w * c_up.y() * hat_d_local.x() * k.z() + 2 * w * c_up.x() * hat_d_local.y() * k.z()
)/(
2 * (c_right.z() * (c_up.y() * hat_d_local.x() - c_up.x() * hat_d_local.y()) + c_right.y() * (-c_up.z() * hat_d_local.x() + c_up.x() * hat_d_local.z()) + c_right.x() * (c_up.z() * hat_d_local.y() - c_up.y() * hat_d_local.z()))
);
double y2 =
(
-c_right.z() * c_up.y() * hat_d_local.x() - h * c_right.z() * c_up.y() * hat_d_local.x() + c_right.y() * c_up.z() * hat_d_local.x()
+ h * c_right.y() * c_up.z() * hat_d_local.x() - 2 * h * c_pos.x() * c_right.z() * hat_d_local.y() + c_right.z() * c_up.x() * hat_d_local.y()
+ h * c_right.z() * c_up.x() * hat_d_local.y() - c_right.x() * c_up.z() * hat_d_local.y() - h * c_right.x() * c_up.z() * hat_d_local.y()
+ c_pos.z() * (-2 * h * c_right.y() * hat_d_local.x() + 2 * h * c_right.x() * hat_d_local.y()) + 2 * h * c_pos.x() * c_right.y() * hat_d_local.z()
- c_right.y() * c_up.x() * hat_d_local.z() - h * c_right.y() * c_up.x() * hat_d_local.z() + c_right.x() * c_up.y() * hat_d_local.z()
+ h * c_right.x() * c_up.y() * hat_d_local.z() + 2 * h * c_pos.y() * (c_right.z() * hat_d_local.x() - c_right.x() * hat_d_local.z())
+ 2 * h * c_right.z() * hat_d_local.y() * k.x() - 2 * h * c_right.y() * hat_d_local.z() * k.x() - 2 * h * c_right.z() * hat_d_local.x() * k.y()
+ 2 * h * c_right.x() * hat_d_local.z() * k.y() + 2 * h * c_right.y() * hat_d_local.x() * k.z() - 2 * h * c_right.x() * hat_d_local.y() * k.z()
)/(
2 * (c_right.z() * (-c_up.y() * hat_d_local.x() + c_up.x() * hat_d_local.y()) + c_right.y() * (c_up.z() * hat_d_local.x() - c_up.x() * hat_d_local.z()) + c_right.x() * (-c_up.z() * hat_d_local.y() + c_up.y() * hat_d_local.z()))
);
// STEP 8: The Local Solar Illumination Angle
Vector2D v1 = new Vector2D(0, 1000);
Vector2D v2 = new Vector2D(x2-x1, y2-y1);
if (v2.x() > 0)
{
PixelOut.IlluminationAngle = tools.rad2deg(Math.Acos((v1 * v2) / (v1.norm() * v2.norm())));
}
else
{
PixelOut.IlluminationAngle = tools.rad2deg(2 * Math.PI - Math.Acos((v1 * v2) / (v1.norm() * v2.norm())));
}
PixelOut.exists = true;
return PixelOut;
}
else
{
// next grid sample point
return PixelOut;
}
}