$dy = 1.0 * ($ymax - $ymin) / $nypoints;
$cscale = 240.0 / ($zmax - $zmin);
$x = $xmin;
for ($i = 0; $i < $nxpoints; $i++) {
$y = $ymin;
for ($j = 0; $j < $nypoints; $j++) {
$z1 = func($x, $y);
$z2 = func($x + $dx, $y);
$z3 = func($x + $dx, $y + $dy);
$z4 = func($x, $y + $dy);
$c1 = $cscale * ($z1 - $zmin);
$c2 = $cscale * ($z2 - $zmin);
$c3 = $cscale * ($z3 - $zmin);
$c4 = $cscale * ($z4 - $zmin);
$c = ($c1 + $c2 + $c3 + $c4) / 4;
if ($c < 0) {
$c = 0;
}
if ($c > 239) {
$c = 239;
}
$p3->solidquad($x, $y, $z1, $x + $dx, $y, $z2, $x + $dx, $y + $dy, $z3, $x, $y + $dy, $z4, $c + 16);
$y = $y + $dy;
}
$x = $x + $dx;
}
}
print "Making a nice 3D plot...\n";
drawsolid();
$frame->writeGIF($cmap, "image.gif");
print "Wrote image.gif\n";
