50 lines
1.6 KiB
GLSL
Executable file
50 lines
1.6 KiB
GLSL
Executable file
// Based on work by David Li(http://david.li/waves)
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// GPU FFT using a Stockham formulation
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#version 450
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#ifdef GL_ES
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precision mediump float;
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#endif
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uniform sampler2D texInput;
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in vec2 texCoord;
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out vec4 fragColor;
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const float PI = 3.14159265359;
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const float transformSize = 512.0;
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const float texSize = 512.0;
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const float subtransformSize = 250.0;
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vec2 multiplyComplex(vec2 a, vec2 b) {
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return vec2(a[0] * b[0] - a[1] * b[1], a[1] * b[0] + a[0] * b[1]);
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}
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void main() {
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// #ifdef HORIZONTAL
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// float index = texCoord.x * transformSize - 0.5;
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// #else
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float index = texCoord.y * transformSize - 0.5;
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// #endif
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float evenIndex = floor(index / subtransformSize) * (subtransformSize * 0.5) + mod(index, subtransformSize * 0.5);
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//transform two complex sequences simultaneously
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// #ifdef HORIZONTAL
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// vec4 even = texture(texInput, vec2(evenIndex + 0.5, texCoord.y * texSize) / transformSize);
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// vec4 odd = texture(texInput, vec2(evenIndex + transformSize * 0.5 + 0.5, texCoord.y * texSize) / transformSize);
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// #else
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// gl_FragCoord.x / texCoord.x * texSize
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vec4 even = texture(texInput, vec2(texCoord.x * texSize, evenIndex + 0.5) / transformSize);
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vec4 odd = texture(texInput, vec2(texCoord.x * texSize, evenIndex + transformSize * 0.5 + 0.5) / transformSize);
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// #endif
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float twiddleArgument = -2.0 * PI * (index / subtransformSize);
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vec2 twiddle = vec2(cos(twiddleArgument), sin(twiddleArgument));
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vec2 outputA = even.xy + multiplyComplex(twiddle, odd.xy);
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vec2 outputB = even.zw + multiplyComplex(twiddle, odd.zw);
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fragColor = vec4(outputA, outputB);
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}
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