From c147e3bff447c67f7b4728fc7e7683b570ef4c86 Mon Sep 17 00:00:00 2001
From: Wojciech Figat <wojtek@figat.pl>
Date: Mon, 6 Jun 2022 13:13:36 +0200
Subject: [PATCH] Minor DDGI optimization

---
 Content/Shaders/GI/DDGI.flax                  |  4 +--
 .../GI/DynamicDiffuseGlobalIllumination.cpp   |  2 +-
 Source/Shaders/GI/DDGI.shader                 | 33 +++++++++----------
 3 files changed, 19 insertions(+), 20 deletions(-)

diff --git a/Content/Shaders/GI/DDGI.flax b/Content/Shaders/GI/DDGI.flax
index 29c746d3b..d68e89a7b 100644
--- a/Content/Shaders/GI/DDGI.flax
+++ b/Content/Shaders/GI/DDGI.flax
@@ -1,3 +1,3 @@
 version https://git-lfs.github.com/spec/v1
-oid sha256:cd93974da1fcb3fad04406e385cb2988f171ef2378017adb9971ac36e5d7b5de
-size 18757
+oid sha256:589d77f14b69b0af963b848ee5a4342c0986304f64296a29d21f45d7e0e6ea88
+size 18536
diff --git a/Source/Engine/Renderer/GI/DynamicDiffuseGlobalIllumination.cpp b/Source/Engine/Renderer/GI/DynamicDiffuseGlobalIllumination.cpp
index 9d86a9585..8521cd1c0 100644
--- a/Source/Engine/Renderer/GI/DynamicDiffuseGlobalIllumination.cpp
+++ b/Source/Engine/Renderer/GI/DynamicDiffuseGlobalIllumination.cpp
@@ -287,12 +287,12 @@ bool DynamicDiffuseGlobalIlluminationPass::Render(RenderContext& renderContext,
     bool debugProbes = false; // TODO: add debug option to draw probes locations -> in Graphics window - Editor-only
     // TODO: configurable via postFx settings (maybe use Global SDF distance?)
     const float indirectLightingIntensity = 1.0f;
+    const float probeHistoryWeight = 0.8f;
     const Vector3 giDistance(2000, 2000, 2000); // GI distance around the view (in each direction)
     const float giResolution = 100.0f; // GI probes placement spacing
     const Int3 probesCounts(Vector3::Ceil(giDistance / giResolution));
     const Vector3 probesDistance = Vector3(probesCounts) * giResolution;
     const int32 probeRaysCount = Math::Min(Math::AlignUp(256, DDGI_TRACE_RAYS_GROUP_SIZE_X), DDGI_TRACE_RAYS_LIMIT); // TODO: make it based on the GI Quality
-    const float probeHistoryWeight = 0.8f;
 
     // Init buffers
     const int32 probesCount = probesCounts.X * probesCounts.Y * probesCounts.Z;
diff --git a/Source/Shaders/GI/DDGI.shader b/Source/Shaders/GI/DDGI.shader
index 6cfb7fa0d..c6a680291 100644
--- a/Source/Shaders/GI/DDGI.shader
+++ b/Source/Shaders/GI/DDGI.shader
@@ -236,9 +236,7 @@ void CS_UpdateProbes(uint3 DispatchThreadId : SV_DispatchThreadID, uint GroupInd
             uint coord = (probeCount + (scrollDirection ? (scrollOffset - 1) : (scrollOffset % probeCount))) % probeCount;
             if (probeCoords[planeIndex] == coord)
             {
-                // Clear probe and return
-                //RWOutput[outputCoords] = float4(0, 0, 0, 0);
-                //if (!skip) RWOutput[outputCoords] = float4(0, 0, 0, 0);
+                // Skip scrolled probes
                 skip = true;
             }
         }
@@ -249,23 +247,20 @@ void CS_UpdateProbes(uint3 DispatchThreadId : SV_DispatchThreadID, uint GroupInd
     if (probeState == DDGI_PROBE_STATE_INACTIVE)
         skip = true;
 
-    // Calculate octahedral projection for probe (unwraps spherical projection into a square)
-    float2 octahedralCoords = GetOctahedralCoords(DispatchThreadId.xy, DDGI_PROBE_RESOLUTION);
-    float3 octahedralDirection = GetOctahedralDirection(octahedralCoords);
-
-    // Load trace rays results into shared memory to reuse across whole thread group
-    uint count = (uint)(ceil((float)(DDGI_TRACE_RAYS_LIMIT) / (float)(DDGI_PROBE_RESOLUTION * DDGI_PROBE_RESOLUTION)));
-    for (uint i = 0; i < count; i++)
+    if (!skip)
     {
-        uint rayIndex = (GroupIndex * count) + i;
-        if (rayIndex >= DDGI.RaysCount)
-            break;
-        CachedProbesTraceRadiance[rayIndex] = ProbesTrace[uint2(rayIndex, probeIndex)];
-        CachedProbesTraceDirection[rayIndex] = GetProbeRayDirection(DDGI, rayIndex);
+        // Load trace rays results into shared memory to reuse across whole thread group
+        uint count = (uint)(ceil((float)(DDGI_TRACE_RAYS_LIMIT) / (float)(DDGI_PROBE_RESOLUTION * DDGI_PROBE_RESOLUTION)));
+        for (uint i = 0; i < count; i++)
+        {
+            uint rayIndex = (GroupIndex * count) + i;
+            if (rayIndex >= DDGI.RaysCount)
+                break;
+            CachedProbesTraceRadiance[rayIndex] = ProbesTrace[uint2(rayIndex, probeIndex)];
+            CachedProbesTraceDirection[rayIndex] = GetProbeRayDirection(DDGI, rayIndex);
+        }
     }
     GroupMemoryBarrierWithGroupSync();
-
-    // TODO: optimize probes updating to build indirect dispatch args and probes indices list before tracing rays and blending irradiance/distance
     if (skip)
     {
         // Clear probe
@@ -273,6 +268,10 @@ void CS_UpdateProbes(uint3 DispatchThreadId : SV_DispatchThreadID, uint GroupInd
         return;
     }
 
+    // Calculate octahedral projection for probe (unwraps spherical projection into a square)
+    float2 octahedralCoords = GetOctahedralCoords(DispatchThreadId.xy, DDGI_PROBE_RESOLUTION);
+    float3 octahedralDirection = GetOctahedralDirection(octahedralCoords);
+
     // Loop over rays
     float4 result = float4(0, 0, 0, 0);
 #if DDGI_PROBE_UPDATE_MODE == 0