Hydrogent: use IBL from the first visible dome light

Author: TheMostDiligent

Hydrogent/interface/HnLight.hpp

@@ -1,5 +1,5 @@
 /*
- *  Copyright 2023-2024 Diligent Graphics LLC
+ *  Copyright 2023-2025 Diligent Graphics LLC
  *
  *  Licensed under the Apache License, Version 2.0 (the "License");
  *  you may not use this file except in compliance with the License.
@@ -102,9 +102,9 @@ class HnLight final : public pxr::HdLight
     float3      m_Position;
     float3      m_Direction;
     GLTF::Light m_Params;
-    bool        m_IsVisible        = true;
-    bool        m_IsShadowMapDirty = true;
-    bool        m_IsTextureDirty   = true;
+    bool        m_IsVisible             = true;
+    bool        m_IsShadowMapDirty      = true;
+    Uint32      m_LightResourcesVersion = ~0u;
 
     float4x4 m_ViewMatrix;
     float4x4 m_ProjMatrix;

Hydrogent/src/HnLight.cpp

@@ -1,5 +1,5 @@
 /*
- *  Copyright 2023-2024 Diligent Graphics LLC
+ *  Copyright 2023-2025 Diligent Graphics LLC
  *
  *  Licensed under the Apache License, Version 2.0 (the "License");
  *  you may not use this file except in compliance with the License.
@@ -433,15 +433,22 @@ void HnLight::Sync(pxr::HdSceneDelegate* SceneDelegate,
 
     const pxr::SdfPath& Id = GetId();
 
-    bool LightDirty = false;
-
+    bool LightDirty      = false;
+    bool IBLCubemapDirty = false;
     {
         bool IsVisible = SceneDelegate->GetVisible(Id);
         if (IsVisible != m_IsVisible)
         {
             m_IsVisible        = IsVisible;
             LightDirty         = true;
             m_IsShadowMapDirty = true;
+            if (m_TypeId == pxr::HdPrimTypeTokens->domeLight)
+            {
+                // NB: we need to update IBL cube maps even if the light became invisible since
+                //     if multiple dome lights were visible, the IBL was precomputed for
+                //     the first one, which might be any of them.
+                IBLCubemapDirty = true;
+            }
         }
     }
 
@@ -527,9 +534,10 @@ void HnLight::Sync(pxr::HdSceneDelegate* SceneDelegate,
             std::string TexturePath = GetTextureFile(*SceneDelegate, Id).GetAssetPath();
             if (TexturePath != m_TexturePath)
             {
-                m_TexturePath    = std::move(TexturePath);
-                LightDirty       = true;
-                m_IsTextureDirty = true;
+                m_TexturePath = std::move(TexturePath);
+                LightDirty    = true;
+                // If the dome light is invisible, we will precompute its IBL cubemaps when it becomes visible
+                IBLCubemapDirty = m_IsVisible;
             }
         }
 
@@ -627,7 +635,7 @@ void HnLight::Sync(pxr::HdSceneDelegate* SceneDelegate,
         if (LightDirty)
             static_cast<HnRenderParam*>(RenderParam)->MakeAttribDirty(HnRenderParam::GlobalAttrib::Light);
 
-        if (m_IsTextureDirty)
+        if (IBLCubemapDirty)
             static_cast<HnRenderParam*>(RenderParam)->MakeAttribDirty(HnRenderParam::GlobalAttrib::LightResources);
     }
 
@@ -637,7 +645,9 @@ void HnLight::Sync(pxr::HdSceneDelegate* SceneDelegate,
 void HnLight::PrecomputeIBLCubemaps(HnRenderDelegate& RenderDelegate)
 {
     VERIFY_EXPR(m_TypeId == pxr::HdPrimTypeTokens->domeLight);
-    if (!m_IsTextureDirty)
+    const HnRenderParam* pRenderParam          = static_cast<const HnRenderParam*>(RenderDelegate.GetRenderParam());
+    const uint32_t       LightResourcesVersion = pRenderParam->GetAttribVersion(HnRenderParam::GlobalAttrib::LightResources);
+    if (LightResourcesVersion == m_LightResourcesVersion)
         return;
 
     IRenderDevice*  pDevice = RenderDelegate.GetDevice();
@@ -681,7 +691,7 @@ void HnLight::PrecomputeIBLCubemaps(HnRenderDelegate& RenderDelegate)
 
     RenderDelegate.GetUSDRenderer()->PrecomputeCubemaps(pCtx, pEnvMap->GetDefaultView(TEXTURE_VIEW_SHADER_RESOURCE));
 
-    m_IsTextureDirty = false;
+    m_LightResourcesVersion = LightResourcesVersion;
 }
 
 } // namespace USD

Hydrogent/src/HnRenderDelegate.cpp

@@ -917,6 +917,12 @@ void HnRenderDelegate::CommitResources(pxr::HdChangeTracker* tracker)
                 HnLight* pLight = it->second;
                 VERIFY_EXPR(pLight->GetTypeId() == pxr::HdPrimTypeTokens->domeLight);
 
+                if (!pLight->IsVisible())
+                {
+                    // Skip invisible dome lights
+                    continue;
+                }
+
                 if (DomeLight == nullptr)
                 {
                     pLight->PrecomputeIBLCubemaps(*this);

Hydrogent/src/Tasks/HnRenderEnvMapTask.cpp

@@ -180,15 +180,33 @@ void HnRenderEnvMapTask::Prepare(pxr::HdTaskContext* TaskCtx,
     EnvMapAttribs.Options       = EnvMapRenderer::OPTION_FLAG_COMPUTE_MOTION_VECTORS;
 
     {
-        const auto& Lights        = pRenderDelegate->GetLights();
-        const auto  dome_light_it = Lights.find(pxr::HdPrimTypeTokens->domeLight);
-        if (dome_light_it != Lights.end())
+        const auto& Lights            = pRenderDelegate->GetLights();
+        auto        dome_lights_range = Lights.equal_range(pxr::HdPrimTypeTokens->domeLight);
+        HnLight*    pDomeLight        = nullptr;
+        for (auto it = dome_lights_range.first; it != dome_lights_range.second; ++it)
         {
-            if (const HnLight* pDomeLight = dome_light_it->second)
+            pDomeLight = it->second;
+            if (pDomeLight == nullptr)
             {
-                EnvMapAttribs.Scale = pDomeLight->GetParams().Color * pDomeLight->GetParams().Intensity;
+                UNEXPECTED("Dome light is null");
+                continue;
+            }
+            VERIFY_EXPR(pDomeLight->GetTypeId() == pxr::HdPrimTypeTokens->domeLight);
+
+            if (pDomeLight->IsVisible())
+            {
+                break;
+            }
+            else
+            {
+                // Skip invisible dome lights
+                pDomeLight = nullptr;
             }
         }
+
+        EnvMapAttribs.Scale = pDomeLight != nullptr ?
+            pDomeLight->GetParams().Color * pDomeLight->GetParams().Intensity :
+            float3{0};
     }
 
     bool UseReverseDepth = false;