From 9aedb6158478aaa48200db495bd7551ff924aa8c Mon Sep 17 00:00:00 2001
From: Isaac <isaacbd@gmail.com>
Date: Thu, 22 Jun 2023 23:21:54 +0200
Subject: [PATCH] Add gauss-4tap

---
 blurs/gauss_4tap.slangp                     | 13 ++++++++
 blurs/shaders/gauss_4tap/common.slang       | 21 ++++++++++++
 blurs/shaders/gauss_4tap/gauss_2tap_h.slang | 37 +++++++++++++++++++++
 blurs/shaders/gauss_4tap/gauss_2tap_v.slang | 37 +++++++++++++++++++++
 blurs/shaders/gauss_4tap/parameters.slang   |  6 ++++
 5 files changed, 114 insertions(+)
 create mode 100644 blurs/gauss_4tap.slangp
 create mode 100644 blurs/shaders/gauss_4tap/common.slang
 create mode 100644 blurs/shaders/gauss_4tap/gauss_2tap_h.slang
 create mode 100644 blurs/shaders/gauss_4tap/gauss_2tap_v.slang
 create mode 100644 blurs/shaders/gauss_4tap/parameters.slang

diff --git a/blurs/gauss_4tap.slangp b/blurs/gauss_4tap.slangp
new file mode 100644
index 0000000..3753fbc
--- /dev/null
+++ b/blurs/gauss_4tap.slangp
@@ -0,0 +1,13 @@
+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
diff --git a/blurs/shaders/gauss_4tap/common.slang b/blurs/shaders/gauss_4tap/common.slang
new file mode 100644
index 0000000..c603fa8
--- /dev/null
+++ b/blurs/shaders/gauss_4tap/common.slang
@@ -0,0 +1,21 @@
+/*
+    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);
+}
diff --git a/blurs/shaders/gauss_4tap/gauss_2tap_h.slang b/blurs/shaders/gauss_4tap/gauss_2tap_h.slang
new file mode 100644
index 0000000..c05fd2e
--- /dev/null
+++ b/blurs/shaders/gauss_4tap/gauss_2tap_h.slang
@@ -0,0 +1,37 @@
+#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));
+}
diff --git a/blurs/shaders/gauss_4tap/gauss_2tap_v.slang b/blurs/shaders/gauss_4tap/gauss_2tap_v.slang
new file mode 100644
index 0000000..7a8e257
--- /dev/null
+++ b/blurs/shaders/gauss_4tap/gauss_2tap_v.slang
@@ -0,0 +1,37 @@
+#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));
+}
diff --git a/blurs/shaders/gauss_4tap/parameters.slang b/blurs/shaders/gauss_4tap/parameters.slang
new file mode 100644
index 0000000..09e9cfd
--- /dev/null
+++ b/blurs/shaders/gauss_4tap/parameters.slang
@@ -0,0 +1,6 @@
+// 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