Add dual filtering blur filter (#360)

* Add dual filtering blur filter

* Slight docs update

blurs/dual_filter_2_pass.slangp

@@ -0,0 +1,31 @@
+shaders = 4
+
+shader0 = shaders/kawase/linearize.slang
+filter_linear0 = false
+scale_type0 = source
+scale_x0 = 1.0
+scale_y0 = 1.0
+float_framebuffer0 = true
+
+shader1 = shaders/dual_filter_downsample.slang
+filter_linear1 = true
+scale_type1 = source
+scale_x1 = 0.5
+scale_y1 = 0.5
+float_framebuffer1 = true
+wrap_mode1 = mirrored_repeat
+
+shader2 = shaders/dual_filter_upsample.slang
+filter_linear2 = true
+scale_type2 = source
+scale_x2 = 2.0
+scale_y2 = 2.0
+float_framebuffer2 = true
+wrap_mode2 = mirrored_repeat
+
+shader3 = shaders/kawase/delinearize.slang
+filter_linear3 = true
+scale_type3 = viewport
+scale_x3 = 1.0
+scale_y3 = 1.0
+float_framebuffer3 = true

blurs/dual_filter_4_pass.slangp

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+shaders = 6
+
+shader0 = shaders/kawase/linearize.slang
+filter_linear0 = false
+scale_type0 = source
+scale_x0 = 1.0
+scale_y0 = 1.0
+float_framebuffer0 = true
+
+shader1 = shaders/dual_filter_downsample.slang
+filter_linear1 = true
+scale_type1 = source
+scale_x1 = 0.5
+scale_y1 = 0.5
+float_framebuffer1 = true
+wrap_mode1 = mirrored_repeat
+
+shader2 = shaders/dual_filter_downsample.slang
+filter_linear2 = true
+scale_type2 = source
+scale_x2 = 0.5
+scale_y2 = 0.5
+float_framebuffer2 = true
+wrap_mode2 = mirrored_repeat
+
+shader3 = shaders/dual_filter_upsample.slang
+filter_linear3 = true
+scale_type3 = source
+scale_x3 = 2.0
+scale_y3 = 2.0
+float_framebuffer3 = true
+wrap_mode3 = mirrored_repeat
+
+shader4 = shaders/dual_filter_upsample.slang
+filter_linear4 = true
+scale_type4 = source
+scale_x4 = 2.0
+scale_y4 = 2.0
+float_framebuffer4 = true
+wrap_mode4 = mirrored_repeat
+
+shader5 = shaders/kawase/delinearize.slang
+filter_linear5 = true
+scale_type5 = viewport
+scale_x5 = 1.0
+scale_y5 = 1.0
+float_framebuffer5 = true
+

blurs/dual_filter_6_pass.slangp

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+shaders = 8
+
+shader0 = shaders/kawase/linearize.slang
+filter_linear0 = false
+scale_type0 = source
+scale_x0 = 1.0
+scale_y0 = 1.0
+float_framebuffer0 = true
+
+shader1 = shaders/dual_filter_downsample.slang
+filter_linear1 = true
+scale_type1 = source
+scale_x1 = 0.5
+scale_y1 = 0.5
+float_framebuffer1 = true
+wrap_mode1 = mirrored_repeat
+
+shader2 = shaders/dual_filter_downsample.slang
+filter_linear2 = true
+scale_type2 = source
+scale_x2 = 0.5
+scale_y2 = 0.5
+float_framebuffer2 = true
+wrap_mode2 = mirrored_repeat
+
+shader3 = shaders/dual_filter_downsample.slang
+filter_linear3 = true
+scale_type3 = source
+scale_x3 = 0.5
+scale_y3 = 0.5
+float_framebuffer3 = true
+wrap_mode3 = mirrored_repeat
+
+shader4 = shaders/dual_filter_upsample.slang
+filter_linear4 = true
+scale_type4 = source
+scale_x4 = 2.0
+scale_y4 = 2.0
+float_framebuffer4 = true
+wrap_mode4 = mirrored_repeat
+
+shader5 = shaders/dual_filter_upsample.slang
+filter_linear5 = true
+scale_type5 = source
+scale_x5 = 2.0
+scale_y5 = 2.0
+float_framebuffer5 = true
+wrap_mode5 = mirrored_repeat
+
+shader6 = shaders/dual_filter_upsample.slang
+filter_linear6 = true
+scale_type6 = source
+scale_x6 = 2.0
+scale_y6 = 2.0
+float_framebuffer6 = true
+wrap_mode6 = mirrored_repeat
+
+shader7 = shaders/kawase/delinearize.slang
+filter_linear7 = true
+scale_type7 = viewport
+scale_x7 = 1.0
+scale_y7 = 1.0
+float_framebuffer7 = true

blurs/shaders/dual_filter_downsample.slang

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+#version 450
+
+// See dual_filter_parameters.slang for copyright and other information.
+
+#include "dual_filter_parameters.slang"
+
+layout(push_constant) uniform Push {
+    vec4 SourceSize;
+    vec4 OriginalSize;
+    vec4 OutputSize;
+    uint FrameCount;
+    float BLUR_STRENGTH;
+}
+param;
+
+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 halfpixel = 0.5 * param.SourceSize.zw * param.BLUR_STRENGTH;
+    vec3 sum = texture(Source, vTexCoord).rgb * 4.0;
+    sum += texture(Source, vTexCoord - halfpixel).rgb;
+    sum += texture(Source, vTexCoord + halfpixel).rgb;
+    sum += texture(Source, vTexCoord + vec2(halfpixel.x, -halfpixel.y)).rgb;
+    sum += texture(Source, vTexCoord - vec2(halfpixel.x, -halfpixel.y)).rgb;
+    FragColor = vec4(sum * 0.125, 1.0);
+}

blurs/shaders/dual_filter_parameters.slang

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+/*
+    Dual filter v1.0, ported to Slang by fishku
+    Copyright (C) 2023
+    Public domain license (CC0)
+
+    Follows the notes of the SIGGRAPH 2015 talk here:
+    https://community.arm.com/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-20-66/siggraph2015_2D00_mmg_2D00_marius_2D00_notes.pdf
+    Dual filtering is a fast large-radius blur that approximates a Gaussian blur. It is closely
+    related to the popular blur filter by Kawase, but runs faster at equal quality.
+
+    How it works: Any number of downsampling passes are chained with the same number of upsampling
+    passes in an hourglass configuration. Both types of resampling passes exploit bilinear
+    interpolation with carefully chosen coordinates and weights to produce a smooth output.
+    There are just 5 + 8 = 13 texture samples per combined down- and upsampling pass.
+    The effective blur radius increases with the number of passes.
+
+    This implementation adds a configurable blur strength which can diminish or accentuate the
+    effect compared to the reference implementation, equivalent to strength 1.0.
+
+    Changelog:
+    v1.0: Initial release.
+*/
+
+// clang-format off
+#pragma parameter DUAL_FILTER_SETTINGS "=== Dual filter v1.0 settings ===" 0.0 0.0 1.0 1.0
+#pragma parameter BLUR_STRENGTH "Blur strength" 1.0 0.6 5.0 0.1
+// clang-format on

blurs/shaders/dual_filter_upsample.slang

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+#version 450
+
+// See dual_filter_parameters.slang for copyright and other information.
+
+#include "dual_filter_parameters.slang"
+
+layout(push_constant) uniform Push {
+    vec4 SourceSize;
+    vec4 OriginalSize;
+    vec4 OutputSize;
+    uint FrameCount;
+    float BLUR_STRENGTH;
+}
+param;
+
+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 halfpixel = 0.5 * param.SourceSize.zw * param.BLUR_STRENGTH;
+    vec3 sum = texture(Source, vTexCoord + vec2(-halfpixel.x * 2.0, 0.0)).rgb;
+    sum += texture(Source, vTexCoord + vec2(-halfpixel.x, halfpixel.y)).rgb * 2.0;
+    sum += texture(Source, vTexCoord + vec2(0.0, halfpixel.y * 2.0)).rgb;
+    sum += texture(Source, vTexCoord + vec2(halfpixel.x, halfpixel.y)).rgb * 2.0;
+    sum += texture(Source, vTexCoord + vec2(halfpixel.x * 2.0, 0.0)).rgb;
+    sum += texture(Source, vTexCoord + vec2(halfpixel.x, -halfpixel.y)).rgb * 2.0;
+    sum += texture(Source, vTexCoord + vec2(0.0, -halfpixel.y * 2.0)).rgb;
+    sum += texture(Source, vTexCoord + vec2(-halfpixel.x, -halfpixel.y)).rgb * 2.0;
+    FragColor = vec4(sum / 12.0, 1.0);
+}