Add SSAO resolution scale

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- SSAO resolution scale (#1423, **@tomas7770**).
+
 ### Changed
 
 - Make SSAO optional (#1396, **@tomas7770**).

engine/assets/render/ssao_blur.fs

@@ -5,11 +5,13 @@ uniform sampler2D ssaoTexture;
 uniform vec2 viewportOffset;
 uniform vec2 viewportSize;
 
+uniform float resolutionScale;
+
 layout (location = 0) out float color;
 
 void main() {
     vec2 uv = fragUv * viewportSize + viewportOffset;
-    vec2 texelSize = 1.0 / vec2(textureSize(ssaoTexture, 0));
+    vec2 texelSize = resolutionScale / vec2(textureSize(ssaoTexture, 0));
     float result = 0.0;
     for (int x = -2; x < 2; ++x)
     {

engine/include/cubos/engine/render/ssao/ssao.hpp

@@ -22,6 +22,9 @@ namespace cubos::engine
         /// @brief Size of the SSAO textures, in pixels.
         glm::uvec2 size = {0, 0};
 
+        /// @brief Scale value to configure SSAO texture size.
+        float resolutionScale = 0.5F;
+
         /// @brief Number of samples to use.
         int samples = 64;
 

engine/src/render/ssao/plugin.cpp

@@ -29,6 +29,7 @@
 CUBOS_DEFINE_TAG(cubos::engine::drawToSSAOTag);
 
 #define MAX_KERNEL_SIZE 64
+#define MAX_SSAO_RESOLUTION 2.0F
 
 namespace
 {
@@ -60,6 +61,7 @@
         ShaderBindingPoint blurSSAOBP;
         ShaderBindingPoint blurViewportOffsetBP;
         ShaderBindingPoint blurViewportSizeBP;
+        ShaderBindingPoint blurResolutionScaleBP;
         VertexArray blurScreenQuad;
 
         ConstantBuffer perSceneCB;
@@ -86,8 +88,9 @@
             blurSSAOBP = blurPipeline->getBindingPoint("ssaoTexture");
             blurViewportOffsetBP = blurPipeline->getBindingPoint("viewportOffset");
             blurViewportSizeBP = blurPipeline->getBindingPoint("viewportSize");
-            CUBOS_ASSERT(blurSSAOBP && blurViewportOffsetBP && blurViewportSizeBP,
-                         "ssaoTexture, viewportOffset and viewportSize binding points must exist");
+            blurResolutionScaleBP = blurPipeline->getBindingPoint("resolutionScale");
+            CUBOS_ASSERT(blurSSAOBP && blurViewportOffsetBP && blurViewportSizeBP && blurResolutionScaleBP,
+                         "ssaoTexture, viewportOffset, viewportSize and resolutionScale binding points must exist");
             generateScreenQuad(renderDevice, blurPipeline, blurScreenQuad);
 
             perSceneCB = renderDevice.createConstantBuffer(sizeof(PerScene), nullptr, Usage::Dynamic);
@@ -197,15 +200,28 @@
                     }
 
                     // Check if we need to resize the SSAO textures.
-                    if (ssao.size != gBuffer.size)
+                    if (ssao.resolutionScale > MAX_SSAO_RESOLUTION)
                     {
-                        ssao.size = gBuffer.size;
+                        // There's probably not much benefit to a scale larger than 1.0, so don't allow very large scale
+                        CUBOS_WARN("SSAO resolution scale is too large, clamping to {}", MAX_SSAO_RESOLUTION);
+                        ssao.resolutionScale = MAX_SSAO_RESOLUTION;
+                    }
+                    else if (ssao.resolutionScale <= 0.0F)
+                    {
+                        CUBOS_WARN("SSAO resolution scale must be positive, setting to 0.5");
+                        ssao.resolutionScale = 0.5F;
+                    }
+                    auto ssaoConfigSize = glm::uvec2(float(gBuffer.size.x) * ssao.resolutionScale,
+                                                     float(gBuffer.size.y) * ssao.resolutionScale);
+                    if (ssao.size != ssaoConfigSize)
+                    {
+                        ssao.size = ssaoConfigSize;
 
                         // Prepare common texture description.
                         Texture2DDesc desc{};
                         desc.format = TextureFormat::R32Float;
-                        desc.width = gBuffer.size.x;
-                        desc.height = gBuffer.size.y;
+                        desc.width = ssao.size.x;
+                        desc.height = ssao.size.y;
                         desc.usage = Usage::Dynamic;
 
                         // Create base and blur textures.
@@ -268,6 +284,7 @@
                     state.blurSSAOBP->bind(ssao.baseTexture);
                     state.blurViewportOffsetBP->setConstant(drawsTo.viewportOffset);
                     state.blurViewportSizeBP->setConstant(drawsTo.viewportSize);
+                    state.blurResolutionScaleBP->setConstant(ssao.resolutionScale);
                     rd.setVertexArray(state.blurScreenQuad);
                     rd.drawTriangles(0, 6);
                 }

engine/src/render/ssao/ssao.cpp

@@ -8,6 +8,7 @@
 {
     return core::ecs::TypeBuilder<SSAO>("cubos::engine::SSAO")
         .withField("size", &SSAO::size)
+        .withField("resolutionScale", &SSAO::resolutionScale)
         .withField("samples", &SSAO::samples)
         .withField("radius", &SSAO::radius)
         .withField("bias", &SSAO::bias)