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/****************************************************************************
Xplanet 0.94 - render an image of a planet into an X window
Copyright (C) 2002 Hari Nair <hari@alumni.caltech.edu>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
****************************************************************************/
#ifndef RING_H
#define RING_H
class Location;
class Ring
{
public:
Ring();
~Ring();
// Compute the distance of the edge of Saturn's shadow on the
// rings as a function of longitude.
void buildShadowRadiusTable();
// get the radius of the ring shadowing the specified location on
// the planet
double getShadowRadius(const Location &sunloc, const Location &point);
// get the equation of the equatorial plane
void getPlane(double &A, double &B, double &C, double &D);
// check if the specified part of the ring is in shadow
bool isInShadow(const double lon, const double r);
// get the brightness on the lit side
double getBrightness(const double lon, const double r);
// get the brightness on the dark side
double getBrightness(const double lon, const double r, const double t);
double getTransparency(const double r);
// set the size of each pixel, used to window average the ring
// brightness/transparency
void setDistPerPixel(const double d);
private:
double r_out; // outer ring radius, units of saturn radii
double dr_b; // resolution of brightness grid
double dr_t; // resolution of transparency grid
double dist_per_pixel; /* size of each pixel at the ring plane,
units of saturn radii */
int num_t;
double *radius_t;
double *transparency;
int window_t; // each pixel contains this many transparency points
int num_b;
double *radius_b;
double *brightness;
int window_b; // each pixel contains this many brightness points
int num_s;
double *shadow_cosangle;
double *shadow_radius;
double sunrot[3][3]; /* rotation matrix to shift the viewpoint
to the sun */
// get the outer radius of the shadow of the planet on the rings
double getShadowRadius(const double x);
// get a window average of array
double getValue(const double *array, const int size, const int window,
const double dr, const double r);
// get a window average of array, accounts for shadowing by the planet
double getValue(const double *array, const int size, const int window,
const double dr, const double r, const double lon);
};
extern Ring satring;
#endif
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