46 lines
870 B
GLSL
46 lines
870 B
GLSL
#version 110
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uniform sampler2D tex;
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uniform bool perspective;
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varying vec2 q;
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varying vec2 b1;
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varying vec2 b2;
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varying vec2 b3;
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varying vec2 vTexCoord;
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float Wedge2D(vec2 v, vec2 w) {
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return (v.x*w.y) - (v.y*w.x);
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}
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void main(void) {
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if (perspective) {
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gl_FragColor = texture2D(tex, vTexCoord);
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} else {
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float A = Wedge2D(b2, b3);
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float B = Wedge2D(b3, q) - Wedge2D(b1, b2);
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float C = Wedge2D(b1, q);
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vec2 uv;
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// solve for v
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if (abs(A) < 0.001) {
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uv.y = -C/B;
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} else {
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float discrim = B*B - 4.0*A*C;
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uv.y = 0.5 * (-B + sqrt(discrim)) / A;
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}
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// solve for u
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vec2 denom = b1 + uv.y * b3;
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if (abs(denom.x) > abs(denom.y)) {
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uv.x = (q.x - b2.x * uv.y) / denom.x;
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} else {
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uv.x = (q.y - b2.y * uv.y) / denom.y;
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}
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uv.y = 1.0 - uv.y;
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gl_FragColor = texture2D(tex, uv);
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}
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} |