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52 lines
1.0 KiB
52 lines
1.0 KiB
#version 100
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precision mediump float;
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#define MAX_SPOTS 4
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#define RADIUS 256.0
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#define INNER 200.0
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// Inputs
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// array of spotlight positions
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uniform vec2 spots[MAX_SPOTS];
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uniform float screenWidth; // width of the screen
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void main()
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{
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float alpha;
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// get the position of the current fragment (screen coordinates!)
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vec2 pos = vec2(gl_FragCoord.x, gl_FragCoord.y);
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// find out which spotlight is nearest
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float d = 65000.0; // some high value
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float di = 0.0;
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for (int i = 0; i < MAX_SPOTS; i++)
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{
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di = distance(pos, spots[i]);
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if (d > di) d = di;
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}
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// d now equals distance to nearest spot...
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if (d > RADIUS) {
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alpha = 1.0;
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} else {
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if (d < INNER) {
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alpha = 0.0;
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} else {
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alpha = (d - INNER) / (RADIUS - INNER);
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}
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}
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// right hand side of screen is dimly lit, could make the
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// threshold value user definable.
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if (pos.x > screenWidth/2.0 && alpha > 0.9) {
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alpha = 0.9;
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}
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// could make the black out colour user definable...
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gl_FragColor = vec4( 0, 0, 0, alpha);
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}
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