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<?
# Plot a 3D function
require "gifplot.php";
# Here is the function to plot
function func($x, $y) {
return 5*cos(2*sqrt($x*$x+$y*$y))*exp(-0.3*sqrt($x*$x+$y*$y));
}
# Here are some plotting parameters
$xmin = -5.0;
$xmax = 5.0;
$ymin = -5.0;
$ymax = 5.0;
$zmin = -5.0;
$zmax = 5.0;
# Grid resolution
$nxpoints = 60;
$nypoints = 60;
$cmap = new_ColorMap("cmap");
$frame = new_FrameBuffer(500,500);
FrameBuffer_clear($frame, BLACK);
$p3 = new_Plot3D($frame,$xmin,$ymin,$zmin,$xmax,$ymax,$zmax);
Plot3D_lookat($p3, 2*($zmax-$zmin));
Plot3D_autoperspective($p3, 40);
Plot3D_rotu($p3, 60);
Plot3D_rotr($p3, 30);
Plot3D_rotd($p3, 10);
function drawsolid() {
global $p3;
global $xmax;
global $xmin;
global $ymax;
global $ymin;
global $zmin;
global $zmax;
global $nxpoints;
global $nypoints;
Plot3D_clear($p3, BLACK);
Plot3D_start($p3);
$dx = 1.0*($xmax-$xmin)/$nxpoints;
$dy = 1.0*($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) { $c = 239; }
Plot3D_solidquad($p3, $x,$y,$z1,$x+$dx,$y,$z2,$x+$dx,$y+$dy,$z3,$x,$y+$dy,$z4,$c+16);
$y = $y + $dy;
}
$x = $x + $dx;
}
}
print "Making a nice 3D plot...\n";
drawsolid();
FrameBuffer_writeGIF($frame, $cmap,"image.gif");
print "Wrote image.gif\n";
?>
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