Add gauss-4tap

blurs/gauss_4tap.slangp

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+shaders = 2
+
+shader0 = shaders/gauss_4tap/gauss_2tap_h.slang
+filter_linear0 = true
+scale_type0 = source
+scale0 = 1.0
+wrap_mode0 = mirrored_repeat
+
+shader1 = shaders/gauss_4tap/gauss_2tap_v.slang
+filter_linear1 = true
+scale_type1 = source
+scale1 = 1.0
+wrap_mode1 = mirrored_repeat

blurs/shaders/gauss_4tap/common.slang

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+/*
+    Gauss-4tap v1.0 by fishku
+    Copyright (C) 2023
+    Public domain license (CC0)
+
+    Simple two-pass Gaussian blur filter which does two taps per pass.
+    Idea based on:
+    https://www.rastergrid.com/blog/2010/09/efficient-gaussian-blur-with-linear-sampling/
+
+    Changelog:
+    v1.0: Initial release.
+*/
+
+// Finds the offset so that two samples drawn with linear filtering at that
+// offset from a central pixel, multiplied with 1/2 each, sum up to a 3-sample
+// approximation of the Gaussian sampled at pixel centers.
+float get_offset(float sigma) {
+    // Weight at x = 0 evaluates to 1 for all values of sigma.
+    const float w = exp(-1.0 / (sigma * sigma));
+    return 2.0 * w / (2.0 * w + 1.0);
+}

blurs/shaders/gauss_4tap/gauss_2tap_h.slang

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+#version 450
+
+// See common.slang for copyright and other information.
+
+#include "parameters.slang"
+
+layout(push_constant) uniform Push {
+    vec4 SourceSize;
+    float SIGMA;
+}
+param;
+
+#include "common.slang"
+
+layout(std140, set = 0, binding = 0) uniform UBO { mat4 MVP; }
+global;
+
+#pragma stage vertex
+layout(location = 0) in vec4 Position;
+layout(location = 1) in vec2 TexCoord;
+layout(location = 0) out vec2 vTexCoord;
+
+void main() {
+    gl_Position = global.MVP * Position;
+    vTexCoord = TexCoord;
+}
+
+#pragma stage fragment
+layout(location = 0) in vec2 vTexCoord;
+layout(location = 0) out vec4 FragColor;
+layout(set = 0, binding = 2) uniform sampler2D Source;
+
+void main() {
+    const vec2 offset = vec2(get_offset(param.SIGMA) * param.SourceSize.z, 0.0);
+    FragColor = 0.5 * (texture(Source, vTexCoord - offset) +
+                       texture(Source, vTexCoord + offset));
+}

blurs/shaders/gauss_4tap/gauss_2tap_v.slang

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+#version 450
+
+// See common.slang for copyright and other information.
+
+#include "parameters.slang"
+
+layout(push_constant) uniform Push {
+    vec4 SourceSize;
+    float SIGMA;
+}
+param;
+
+#include "common.slang"
+
+layout(std140, set = 0, binding = 0) uniform UBO { mat4 MVP; }
+global;
+
+#pragma stage vertex
+layout(location = 0) in vec4 Position;
+layout(location = 1) in vec2 TexCoord;
+layout(location = 0) out vec2 vTexCoord;
+
+void main() {
+    gl_Position = global.MVP * Position;
+    vTexCoord = TexCoord;
+}
+
+#pragma stage fragment
+layout(location = 0) in vec2 vTexCoord;
+layout(location = 0) out vec4 FragColor;
+layout(set = 0, binding = 2) uniform sampler2D Source;
+
+void main() {
+    const vec2 offset = vec2(0.0, get_offset(param.SIGMA) * param.SourceSize.w);
+    FragColor = 0.5 * (texture(Source, vTexCoord - offset) +
+                       texture(Source, vTexCoord + offset));
+}

blurs/shaders/gauss_4tap/parameters.slang

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+// See common.slang for copyright and other information.
+
+// clang-format off
+#pragma parameter GAUSS_4TAP_SETTINGS "=== Gauss-4tap v1.0 settings ===" 0.0 0.0 1.0 1.0
+#pragma parameter SIGMA "Blur radius" 1.0 0.0 2.0 0.05
+// clang-format on