Improve bloom downsample performance

https://www.shadertoy.com/view/cslczj

include/garden/system/render/bloom.hpp

@@ -42,11 +42,15 @@ class BloomRenderSystem final : public System, public Singleton<BloomRenderSyste
 	/**
 	 * @brief First downsample step shader variant.
 	 */
-	static constexpr uint8 downsample0Variant = 0;
+	static constexpr uint8 downsampleFirstVariant = 0;
+	/**
+	 * @brief 6x6 downsample step shader variant.
+	 */
+	static constexpr uint8 downsample6x6Variant = 1;
 	/**
 	 * @brief Generic downsample step shader variant.
 	 */
-	static constexpr uint8 downsampleVariant = 1;
+	static constexpr uint8 downsampleBaseVariant = 2;
 private:
 	ID<GraphicsPipeline> downsamplePipeline = {};
 	ID<GraphicsPipeline> upsamplePipeline = {};
@@ -103,7 +107,7 @@ class BloomRenderSystem final : public System, public Singleton<BloomRenderSyste
 	 */
 	ID<GraphicsPipeline> getDownsamplePipeline();
 	/**
-	 * @brief Returns bloom upwnsample graphics pipeline.
+	 * @brief Returns bloom upsample graphics pipeline.
 	 */
 	ID<GraphicsPipeline> getUpsamplePipeline();
 	/**

resources/shaders/bloom/downsample.frag

@@ -16,8 +16,9 @@
 #include "common/gbuffer.gsl"
 #include "common/tone-mapping.gsl"
 
-#variantCount 2
-#define DOWNSAMPLE_0_VARIANT 0
+#variantCount 3
+#define DOWNSAMPLE_FIRST_VARIANT 0
+#define DOWNSAMPLE_6X6_VARIANT 1
 
 spec const bool USE_THRESHOLD = false;
 spec const bool USE_ANTI_FLICKERING = true;
@@ -100,16 +101,47 @@ float3 downsample(sampler2D srcTexture, float2 texCoords, float threshold, bool
 	return color;
 }
 
+//**********************************************************************************************************************
+float3 downsample6x6(sampler2D srcTexture, float2 texCoords)
+{
+	const float o  = 1.5f + 0.261629f;
+	const float wa = 7.46602f / 32.0f;
+	const float wb = 1.0f - wa * 2.0f;
+	const float wab = wa * wb;
+	const float waa = wa * wa;
+	const float wbb = wb * wb;
+
+	float2 size = textureSize(srcTexture, 0);
+	size = (1.0f / size) * o;
+
+	float3 c  = texture(srcTexture, texCoords + float2(0.0f            )).rgb;
+	float3 l  = texture(srcTexture, texCoords + float2(-size.x,    0.0f)).rgb;
+	float3 r  = texture(srcTexture, texCoords + float2( size.x,    0.0f)).rgb;
+	float3 b  = texture(srcTexture, texCoords + float2(   0.0f, -size.y)).rgb;
+	float3 t  = texture(srcTexture, texCoords + float2(   0.0f,  size.y)).rgb;
+	float3 lb = texture(srcTexture, texCoords + float2(-size.x, -size.y)).rgb;
+	float3 rb = texture(srcTexture, texCoords + float2( size.x, -size.y)).rgb;
+	float3 lt = texture(srcTexture, texCoords + float2(-size.x,  size.y)).rgb;
+	float3 rt = texture(srcTexture, texCoords + float2( size.x,  size.y)).rgb;
+
+	return (c * wbb + (l * wab + (r * wab + (b * wab + (t * wab + 
+		(lb * waa + (rb * waa + (lt * waa + (rt * waa)))))))));
+}
+
 void main()
 {
 	float3 color;
 
-	if (gsl.variant == DOWNSAMPLE_0_VARIANT)
+	if (gsl.variant == DOWNSAMPLE_FIRST_VARIANT)
 	{
 		color = downsample(srcTexture, fs.texCoords,
 			pc.threshold, USE_THRESHOLD, USE_ANTI_FLICKERING);
 		color = max(color, 0.0001f);
 	}
+	else if (gsl.variant == DOWNSAMPLE_6X6_VARIANT)
+	{
+		color = downsample6x6(srcTexture, fs.texCoords);
+	}
 	else
 	{
 		color = downsample(srcTexture, fs.texCoords, 0.0f, false, false);

source/system/render/bloom.cpp

@@ -48,12 +48,10 @@ static ID<Image> createBloomBuffer(vector<ID<ImageView>>& imageViews)
 	return image;
 }
 
-//**********************************************************************************************************************
 static void createBloomFramebuffers(const vector<ID<ImageView>>& imageViews, vector<ID<Framebuffer>>& framebuffers)
 {
 	auto graphicsSystem = GraphicsSystem::Instance::get();
-	auto framebufferSize = graphicsSystem->getScaledFramebufferSize();
-	framebufferSize = max(framebufferSize / 2u, uint2(1));
+	auto framebufferSize = max(graphicsSystem->getScaledFramebufferSize() / 2u, uint2(1));
 	auto mipCount = (uint8)imageViews.size();
 	framebuffers.resize(mipCount);
 
@@ -104,7 +102,6 @@ static void createBloomDescriptorSets(ID<Image> bloomBuffer,
 	}
 }
 
-//**********************************************************************************************************************
 static ID<GraphicsPipeline> createDownsamplePipeline(
 	ID<Framebuffer> framebuffer, bool useThreshold, bool useAntiFlickering)
 {
@@ -224,17 +221,21 @@ void BloomRenderSystem::preLdrRender()
 
 		SET_GPU_DEBUG_LABEL("Downsample", Color::transparent);
 		framebufferView->beginRenderPass(float4(0.0f));
-		downsamplePipelineView->bind(downsample0Variant);
+		downsamplePipelineView->bind(downsampleFirstVariant);
 		downsamplePipelineView->setViewportScissor();
 		downsamplePipelineView->bindDescriptorSet(descriptorSets[0]);
 		downsamplePipelineView->pushConstants();
 		downsamplePipelineView->drawFullscreen();
 		framebufferView->endRenderPass();
 
-		downsamplePipelineView->bind(downsampleVariant);
 		for (uint8 i = 1; i < mipCount; i++)
 		{
+			framebufferView = graphicsSystem->get(framebuffers[i - 1]);
+			auto framebufferSize = framebufferView->getSize();
+
 			framebufferView = graphicsSystem->get(framebuffers[i]);
+			downsamplePipelineView->bind(framebufferSize.x & 1 || framebufferSize.y & 1 ? 
+				downsampleBaseVariant : downsample6x6Variant);
 			framebufferView->beginRenderPass(float4(0.0f));
 			downsamplePipelineView->setViewportScissor();
 			downsamplePipelineView->bindDescriptorSet(descriptorSets[i]);
@@ -285,7 +286,6 @@ void BloomRenderSystem::gBufferRecreate()
 	}
 }
 
-//**********************************************************************************************************************
 void BloomRenderSystem::setConsts(bool useThreshold, bool useAntiFlickering)
 {
 	if (this->useThreshold == useThreshold && this->useAntiFlickering == useAntiFlickering)
@@ -294,13 +294,13 @@ void BloomRenderSystem::setConsts(bool useThreshold, bool useAntiFlickering)
 	this->useThreshold = useThreshold;
 	this->useAntiFlickering = useAntiFlickering;
 
+	auto graphicsSystem = GraphicsSystem::Instance::get();
+	graphicsSystem->destroy(descriptorSets);
+	descriptorSets.clear();
+
 	if (downsamplePipeline)
 	{
-		auto graphicsSystem = GraphicsSystem::Instance::get();
-		graphicsSystem->destroy(descriptorSets);
-		descriptorSets.clear();
 		graphicsSystem->destroy(downsamplePipeline);
-
 		downsamplePipeline = createDownsamplePipeline(getFramebuffers()[0], useThreshold, useAntiFlickering);
 	}
 }