49 lines
1.5 KiB
GLSL
49 lines
1.5 KiB
GLSL
#version 450
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layout(location = 0) in vec2 v_uv;
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layout(location = 0) out vec4 out_color;
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layout(set = 2, binding = 0) uniform sampler2D source;
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layout(set = 3, binding = 0) uniform DownscaleUniforms {
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int algorithm; // 0 = Lanczos2 (ventana 2, ±2 taps), 1 = Lanczos3 (ventana 3, ±3 taps)
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float pad0;
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float pad1;
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float pad2;
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} u;
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// Kernel Lanczos normalizado: sinc(t) * sinc(t/a) para |t| < a, 0 fuera.
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float lanczos(float t, float a) {
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t = abs(t);
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if (t < 0.0001) { return 1.0; }
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if (t >= a) { return 0.0; }
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const float PI = 3.14159265358979;
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float pt = PI * t;
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return (a * sin(pt) * sin(pt / a)) / (pt * pt);
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}
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void main() {
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vec2 src_size = vec2(textureSize(source, 0));
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// Posición en coordenadas de texel (centros de texel en N+0.5)
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vec2 p = v_uv * src_size;
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vec2 p_floor = floor(p);
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float a = (u.algorithm == 0) ? 2.0 : 3.0;
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int win = int(a);
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vec4 color = vec4(0.0);
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float weight_sum = 0.0;
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for (int j = -win; j <= win; j++) {
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for (int i = -win; i <= win; i++) {
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// Centro del texel (i,j) relativo a p_floor
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vec2 tap_center = p_floor + vec2(float(i), float(j)) + 0.5;
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vec2 offset = tap_center - p;
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float w = lanczos(offset.x, a) * lanczos(offset.y, a);
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color += texture(source, tap_center / src_size) * w;
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weight_sum += w;
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}
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}
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out_color = (weight_sum > 0.0) ? (color / weight_sum) : vec4(0.0, 0.0, 0.0, 1.0);
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}
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