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/* Graphics_surface.cpp
*
* Copyright (C) 1992-2011 Paul Boersma
*
* 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include "Graphics.h"
void Graphics_surface (Graphics me, double **z,
long ix1, long ix2, double x1, double x2,
long iy1, long iy2, double y1, double y2,
double minimum, double maximum,
double elevation, double azimuth)
{
double dx, dy;
/* 'sum' is the running sum of the x and y indices of the back corner of each tetragon.
* The x and y indices of the back corner of the backmost tetragon are ix2 and iy2,
* The x and y indices of the front corner of the frontmost tetragon are ix1 and iy1,
* so that the x and y indices of its back corner are ix1 + 1 and iy1 + 1.
*/
long maxsum = ix2 + iy2, minsum = (ix1 + 1) + (iy1 + 1), sum;
(void) elevation; /* BUG */
(void) azimuth; /* BUG */
if (ix2 <= ix1 || iy2 <= iy1) return;
dx = (x2 - x1) / (ix2 - ix1);
dy = (y2 - y1) / (iy2 - iy1);
/* We start at the back of the surface plot.
* This part of the picture may be overdrawn by points more forward.
*/
for (sum = maxsum; sum >= minsum; sum --) {
/* We are going to cycle over a diagonal sequence of points.
* Compute the row boundaries of this sequence.
*/
long iymin = iy1 + 1, iymax = iy2, iy;
if (iymin < sum - ix2) iymin = sum - ix2;
if (iymax > sum - (ix1 + 1)) iymax = sum - (ix1 + 1);
for (iy = iymin; iy <= iymax; iy ++) {
/* Compute the indices of all four points.
*/
long ix = sum - iy;
long ixback = ix, ixfront = ix - 1, ixleft = ix - 1, ixright = ix;
long iyback = iy, iyfront = iy - 1, iyleft = iy, iyright = iy - 1;
/* Compute the world coordinates of all four points.
*/
double xback = x1 + (ixback - ix1) * dx, xright = xback;
double xfront = x1 + (ixfront - ix1) * dx, xleft = xfront;
double yback = y1 + (iyback - iy1) * dy, yleft = yback;
double yfront = y1 + (iyfront - iy1) * dy, yright = yfront;
double zback = z [iyback] [ixback], zfront = z [iyfront] [ixfront];
double zleft = z [iyleft] [ixleft], zright = z [iyright] [ixright];
/* The Graphics library uses a two-dimensional world, so we have to convert
* to 2-D world coordinates, which we call x [0..3] and y [0..3].
* We suppose that world coordinate "x" = 0 is in the centre of the figure,
* and that the left and right borders of the figure have world coordinates -1 and +1.
* Also, we suppose that the bottom and top are around 'minimum' and 'maximum'.
*/
double x [5], y [5];
/* Elevation and azimuth fixed???
*/
double up = 0.3 * (maximum - minimum), xscale = 1 / (x2 - x1), yscale = 1 / (y2 - y1);
/* The back point.
*/
x [0] = (xback - x1) * xscale - (yback - y1) * yscale;
y [0] = up * ((xback - x1) * xscale + (yback - y1) * yscale) + zback;
/* The right point.
*/
x [1] = (xright - x1) * xscale - (yright - y1) * yscale;
y [1] = up * ((xright - x1) * xscale + (yright - y1) * yscale) + zright;
/* The front point.
*/
x [2] = (xfront - x1) * xscale - (yfront - y1) * yscale;
y [2] = up * ((xfront - x1) * xscale + (yfront - y1) * yscale) + zfront;
/* The left point.
*/
x [3] = (xleft - x1) * xscale - (yleft - y1) * yscale;
y [3] = up * ((xleft - x1) * xscale + (yleft - y1) * yscale) + zleft;
/* Paint the tetragon in the average grey value, white at the top.
* This gives the idea of height.
*/
Graphics_setGrey (me, (0.25 * (zback + zright + zfront + zleft) - minimum) / (maximum - minimum));
Graphics_fillArea (me, 4, & x [0], & y [0]);
/* Draw the borders of the tetragon in black.
* This gives the idea of steepness and viewing angle.
*/
Graphics_setGrey (me, 0);
x [4] = x [0]; y [4] = y [0]; /* Close polygon. */
Graphics_polyline (me, 5, & x [0], & y [0]);
}
}
}
/* End of file Graphics_surface.cpp */
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