CameraAttribs: added scene near/far z and depth

Author: TheMostDiligent

Hydrogent/src/Tasks/HnBeginFrameTask.cpp

@@ -534,20 +534,9 @@ void HnBeginFrameTask::UpdateFrameConstants(IDeviceContext* pCtx,
 
             float fNearPlaneZ, fFarPlaneZ;
             ProjMatrix.GetNearFarClipPlanes(fNearPlaneZ, fFarPlaneZ, pDevice->GetDeviceInfo().NDC.MinZ == -1);
-            if (m_Params.UseReverseDepth)
-            {
-                CamAttribs.fNearPlaneZ     = fFarPlaneZ;
-                CamAttribs.fFarPlaneZ      = fNearPlaneZ;
-                CamAttribs.fNearPlaneDepth = 1.f;
-                CamAttribs.fFarPlaneDepth  = 0.f;
-            }
-            else
-            {
-                CamAttribs.fNearPlaneZ     = fNearPlaneZ;
-                CamAttribs.fFarPlaneZ      = fFarPlaneZ;
-                CamAttribs.fNearPlaneDepth = 0.f;
-                CamAttribs.fFarPlaneDepth  = 1.f;
-            }
+            VERIFY_EXPR((!m_Params.UseReverseDepth && (fNearPlaneZ <= fFarPlaneZ)) ||
+                        (m_Params.UseReverseDepth && (fNearPlaneZ >= fFarPlaneZ)));
+            CamAttribs.SetClipPlanes(fNearPlaneZ, fFarPlaneZ);
 
             if (CamAttribs.mView != PrevCamera.mView)
             {

Shaders/Common/public/BasicStructures.fxh

@@ -91,6 +91,12 @@ struct CameraAttribs
     float fNearPlaneDepth;
     float fFarPlaneDepth;
 
+    // Tight scene bounds
+    float fSceneNearZ;
+    float fSceneFarZ; // fSceneNearZ < fSceneFarZ
+    float fSceneNearDepth;
+    float fSceneFarDepth;
+    
     float fHandness;   // +1.0 for right-handed coordinate system, -1.0 for left-handed
     uint  uiFrameIndex;
     float Padding0;
@@ -120,6 +126,26 @@ struct CameraAttribs
     float4x4 mViewProjInv;
 
     float4 f4ExtraData[5]; // Any appliation-specific data
+    
+#ifdef __cplusplus
+    // Set the near and far clip planes z and depth values.
+    //
+    // fNearZ > fFarZ means that the depth buffer is reversed.
+    void SetClipPlanes(float fNearZ, float fFarZ)
+    {
+        bool UseReverseDepth = fNearZ > fFarZ;
+
+        fNearPlaneZ     = UseReverseDepth ? fFarZ  : fNearZ;
+        fFarPlaneZ      = UseReverseDepth ? fNearZ : fFarZ;
+        fNearPlaneDepth = UseReverseDepth ? 1.f : 0.f;
+        fFarPlaneDepth  = UseReverseDepth ? 0.f : 1.f;
+
+        fSceneNearZ     = fNearPlaneZ;
+        fSceneFarZ      = fFarPlaneZ;
+        fSceneNearDepth = fNearPlaneDepth;
+        fSceneFarDepth  = fFarPlaneDepth;
+    }
+#endif
 };
 #ifdef CHECK_STRUCT_ALIGNMENT
     CHECK_STRUCT_ALIGNMENT(CameraAttribs);

Shaders/PBR/private/RenderPBR.psh

@@ -601,9 +601,10 @@ PSOutput main(in VSOutput VSOut,
     }
 #   elif (DEBUG_VIEW == DEBUG_VIEW_SCENE_DEPTH)
     {
-        float CameraZ = DepthToCameraZ(VSOut.ClipPos.z, g_Frame.Camera.mProj);
-        CameraZ = (CameraZ - g_Frame.Camera.fNearPlaneZ) / (g_Frame.Camera.fFarPlaneZ - g_Frame.Camera.fNearPlaneZ);
-        OutColor.rgb = float3(CameraZ, CameraZ, CameraZ);
+        float CameraZ     = DepthToCameraZ(VSOut.ClipPos.z, g_Frame.Camera.mProj);
+        float SceneZRange = max(g_Frame.Camera.fSceneFarZ - g_Frame.Camera.fSceneNearZ, 1e-6);
+        float RelSceneZ   = saturate((CameraZ - g_Frame.Camera.fSceneNearZ) / SceneZRange);
+        OutColor.rgb = float3(RelSceneZ, RelSceneZ, RelSceneZ);
     }
 #   elif (DEBUG_VIEW != DEBUG_VIEW_NONE)
     {