Improved DiffuseProbeGrid blending around the edges of the volume

Signed-off-by: dmcdiarmid-ly <63674186+dmcdiarmid-ly@users.noreply.github.com>

Gems/Atom/Feature/Common/Assets/Shaders/DiffuseGlobalIllumination/DiffuseComposite.azsl

@@ -150,7 +150,7 @@ PSOutput MainPS(VSOutput IN, in uint sampleIndex : SV_SampleIndex)
     float4 encodedNormal = PassSrg::m_normal.Load(screenCoords, sampleIndex);
     float3 normal = DecodeNormalSignedOctahedron(encodedNormal.rgb);
     float4 albedo = PassSrg::m_albedo.Load(screenCoords, sampleIndex);
-    float probeIrradianceBlendWeight = PassSrg::m_downsampledProbeIrradiance.Load(probeIrradianceCoords, sampleIndex).a;
+    float probeIrradianceBlendWeight = saturate(PassSrg::m_downsampledProbeIrradiance.Load(probeIrradianceCoords, sampleIndex).a);
   
     float3 diffuse = float3(0.0f, 0.0f, 0.0f);
     if (probeIrradianceBlendWeight > 0.0f)

Gems/Atom/Feature/Common/Code/Source/DiffuseGlobalIllumination/DiffuseProbeGrid.cpp

@@ -102,8 +102,17 @@ namespace AZ
 
         void DiffuseProbeGrid::SetProbeSpacing(const AZ::Vector3& probeSpacing)
         {
+            // remove previous spacing from the render extents
+            m_renderExtents -= m_probeSpacing;
+
+            // update probe spacing
             m_probeSpacing = probeSpacing;
 
+            // expand the extents by one probe spacing unit in order to blend properly around the edges of the volume
+            m_renderExtents += m_probeSpacing;
+
+            m_obbWs = Obb::CreateFromPositionRotationAndHalfLengths(m_transform.GetTranslation(), m_transform.GetRotation(), m_renderExtents / 2.0f);
+
             // recompute the number of probes since the spacing changed
             UpdateProbeCount();
 
@@ -128,7 +137,8 @@ namespace AZ
         void DiffuseProbeGrid::SetTransform(const AZ::Transform& transform)
         {
             m_transform = transform;
-            m_obbWs = Obb::CreateFromPositionRotationAndHalfLengths(m_transform.GetTranslation(), m_transform.GetRotation(), m_extents / 2.0f);
+
+            m_obbWs = Obb::CreateFromPositionRotationAndHalfLengths(m_transform.GetTranslation(), m_transform.GetRotation(), m_renderExtents / 2.0f);
 
             // probes need to be relocated since the grid position changed
             m_remainingRelocationIterations = DefaultNumRelocationIterations;
@@ -144,11 +154,15 @@ namespace AZ
         void DiffuseProbeGrid::SetExtents(const AZ::Vector3& extents)
         {
             m_extents = extents;
-            m_obbWs = Obb::CreateFromPositionRotationAndHalfLengths(m_transform.GetTranslation(), m_transform.GetRotation(), m_extents / 2.0f);
 
             // recompute the number of probes since the extents changed
             UpdateProbeCount();
 
+            // expand the extents by one probe spacing unit in order to blend properly around the edges of the volume
+            m_renderExtents = m_extents + m_probeSpacing;
+
+            m_obbWs = Obb::CreateFromPositionRotationAndHalfLengths(m_transform.GetTranslation(), m_transform.GetRotation(), m_renderExtents / 2.0f);
+
             // probes need to be relocated since the grid extents changed
             m_remainingRelocationIterations = DefaultNumRelocationIterations;
 
@@ -700,11 +714,11 @@ namespace AZ
             RHI::ShaderInputImageIndex imageIndex;
 
             constantIndex = srgLayout->FindShaderInputConstantIndex(Name("m_modelToWorld"));
-            AZ::Matrix3x4 modelToWorld = AZ::Matrix3x4::CreateFromTransform(m_transform) * AZ::Matrix3x4::CreateScale(m_extents);
+            AZ::Matrix3x4 modelToWorld = AZ::Matrix3x4::CreateFromTransform(m_transform) * AZ::Matrix3x4::CreateScale(m_renderExtents);
             m_renderObjectSrg->SetConstant(constantIndex, modelToWorld);
 
             constantIndex = srgLayout->FindShaderInputConstantIndex(Name("m_modelToWorldInverse"));
-            AZ::Matrix3x4 modelToWorldInverse = AZ::Matrix3x4::CreateFromTransform(m_transform).GetInverseFull();
+            AZ::Matrix3x4 modelToWorldInverse = modelToWorld.GetInverseFull();
             m_renderObjectSrg->SetConstant(constantIndex, modelToWorldInverse);
 
             constantIndex = srgLayout->FindShaderInputConstantIndex(Name("m_obbHalfLengths"));

Gems/Atom/Feature/Common/Code/Source/DiffuseGlobalIllumination/DiffuseProbeGrid.h

@@ -183,11 +183,14 @@ namespace AZ
             // extents of the probe grid
             AZ::Vector3 m_extents = AZ::Vector3(0.0f, 0.0f, 0.0f);
 
+            // expanded extents for rendering the volume
+            AZ::Vector3 m_renderExtents = AZ::Vector3(0.0f, 0.0f, 0.0f);
+
             // probe grid OBB (world space), built from transform and extents
             AZ::Obb m_obbWs;
 
             // per-axis spacing of probes in the grid
-            AZ::Vector3 m_probeSpacing;
+            AZ::Vector3 m_probeSpacing = AZ::Vector3(0.0f, 0.0f, 0.0f);
 
             // per-axis number of probes in the grid
             uint32_t m_probeCountX = 0;