VideoBackends: Use vertex shader depth range if ztexture is used.

Source/Core/VideoBackends/D3D/Render.cpp

@@ -576,8 +576,7 @@ void Renderer::SetViewport()
 
   // If an inverted or oversized depth range is used, we need to calculate the depth range in the
   // vertex shader.
-  if (xfmem.viewport.zRange < 0.0f || fabs(xfmem.viewport.zRange) > 16777215.0f ||
-      fabs(xfmem.viewport.farZ) > 16777215.0f)
+  if (UseVertexDepthRange())
   {
     // We need to ensure depth values are clamped the maximum value supported by the console GPU.
     min_depth = 0.0f;

Source/Core/VideoBackends/D3D12/Render.cpp

@@ -481,8 +481,7 @@ void Renderer::SetViewport()
 
   // If an inverted or oversized depth range is used, we need to calculate the depth range in the
   // vertex shader.
-  if (xfmem.viewport.zRange < 0.0f || fabs(xfmem.viewport.zRange) > 16777215.0f ||
-      fabs(xfmem.viewport.farZ) > 16777215.0f)
+  if (UseVertexDepthRange())
   {
     // We need to ensure depth values are clamped the maximum value supported by the console GPU.
     min_depth = 0.0f;

Source/Core/VideoBackends/OGL/Render.cpp

@@ -1135,17 +1135,16 @@ void Renderer::SetViewport()
     glViewport(iceilf(X), iceilf(Y), iceilf(Width), iceilf(Height));
   }
 
-  // Set the reversed depth range.
-  if (g_ActiveConfig.backend_info.bSupportsOversizedDepthRanges)
+  if (!g_ActiveConfig.backend_info.bSupportsOversizedDepthRanges &&
+      !g_ActiveConfig.backend_info.bSupportsDepthClamp)
   {
-    glDepthRangedNV(max_depth, min_depth);
+    // There's no way to support oversized depth ranges in this situation. Let's just clamp the
+    // range to the maximum value supported by the console GPU and hope for the best.
+    min_depth = MathUtil::Clamp(min_depth, 0.0f, GX_MAX_DEPTH);
+    max_depth = MathUtil::Clamp(max_depth, 0.0f, GX_MAX_DEPTH);
   }
-  else
-  {
-    // If an oversized depth range is used, we need to calculate the depth range in the
-    // vertex shader.
-    if (g_ActiveConfig.backend_info.bSupportsDepthClamp &&
-        (fabs(xfmem.viewport.zRange) > 16777215.0f || fabs(xfmem.viewport.farZ) > 16777215.0f))
+
+  if (UseVertexDepthRange())
   {
     // We need to ensure depth values are clamped the maximum value supported by the console GPU.
     // Taking into account whether the depth range is inverted or not.
@@ -1160,17 +1159,13 @@ void Renderer::SetViewport()
       max_depth = GX_MAX_DEPTH;
     }
   }
-    else
-    {
-      // There's no way to support oversized depth ranges in this situation. Let's just clamp the
-      // range to the maximum value supported by the console GPU and hope for the best.
-      min_depth = MathUtil::Clamp(min_depth, 0.0f, GX_MAX_DEPTH);
-      max_depth = MathUtil::Clamp(max_depth, 0.0f, GX_MAX_DEPTH);
-    }
 
+  // Set the reversed depth range.
+  if (g_ActiveConfig.backend_info.bSupportsOversizedDepthRanges)
+    glDepthRangedNV(max_depth, min_depth);
+  else
     glDepthRangef(max_depth, min_depth);
 }
-}
 
 void Renderer::ClearScreen(const EFBRectangle& rc, bool colorEnable, bool alphaEnable, bool zEnable,
                            u32 color, u32 z)

Source/Core/VideoBackends/Vulkan/Renderer.cpp

@@ -4,7 +4,6 @@
 
 #include "VideoBackends/Vulkan/Renderer.h"
 
-#include <cmath>
 #include <cstddef>
 #include <cstdio>
 #include <limits>
@@ -1657,8 +1656,7 @@ void Renderer::SetViewport()
   // If an oversized or inverted depth range is used, we need to calculate the depth range in the
   // vertex shader.
   // TODO: Inverted depth ranges are bugged in all drivers, which should be added to DriverDetails.
-  if (xfmem.viewport.zRange < 0.0f || fabs(xfmem.viewport.zRange) > 16777215.0f ||
-      fabs(xfmem.viewport.farZ) > 16777215.0f)
+  if (UseVertexDepthRange())
   {
     // We need to ensure depth values are clamped the maximum value supported by the console GPU.
     min_depth = 0.0f;

Source/Core/VideoCommon/BPStructs.cpp

@@ -332,6 +332,8 @@ static void BPWritten(const BPCmd& bp)
   {
     if (bp.changes & 3)
       PixelShaderManager::SetZTextureTypeChanged();
+    if (bp.changes & 12)
+      VertexShaderManager::SetViewportChanged();
 #if defined(_DEBUG) || defined(DEBUGFAST)
     const char* pzop[] = {"DISABLE", "ADD", "REPLACE", "?"};
     const char* pztype[] = {"Z8", "Z16", "Z24", "?"};

Source/Core/VideoCommon/RenderBase.cpp

@@ -940,3 +940,30 @@ void Renderer::DumpFrameToImage(const FrameDumpConfig& config)
   TextureToPng(config.data, config.stride, filename, config.width, config.height, false);
   m_frame_dump_image_counter++;
 }
+
+bool Renderer::UseVertexDepthRange() const
+{
+  // We can't compute the depth range in the vertex shader if we don't support depth clamp.
+  if (!g_ActiveConfig.backend_info.bSupportsDepthClamp)
+    return false;
+
+  if (g_ActiveConfig.backend_info.bSupportsOversizedDepthRanges)
+  {
+    // We support oversized depth ranges, but we need a full depth range if a ztexture is used.
+    return bpmem.ztex2.type != ZTEXTURE_DISABLE;
+  }
+  else
+  {
+    // We need a full depth range if a ztexture is used.
+    if (bpmem.ztex2.type != ZTEXTURE_DISABLE)
+      return true;
+
+    // If an inverted depth range is unsupported, we also need to check if the range is inverted.
+    if (!g_ActiveConfig.backend_info.bSupportsReversedDepthRange && xfmem.viewport.zRange < 0.0f)
+      return true;
+
+    // If an oversized depth range or a ztexture is used, we need to calculate the depth range
+    // in the vertex shader.
+    return fabs(xfmem.viewport.zRange) > 16777215.0f || fabs(xfmem.viewport.farZ) > 16777215.0f;
+  }
+}

Source/Core/VideoCommon/RenderBase.h

@@ -145,6 +145,8 @@ public:
   // Final surface changing
   // This is called when the surface is resized (WX) or the window changes (Android).
   virtual void ChangeSurface(void* new_surface_handle) {}
+  bool UseVertexDepthRange() const;
+
 protected:
   static void CalculateTargetScale(int x, int y, int* scaledX, int* scaledY);
   bool CalculateTargetSize();

Source/Core/VideoCommon/VertexShaderManager.cpp

@@ -391,42 +391,29 @@ void VertexShaderManager::SetConstants()
     constants.pixelcentercorrection[2] = 1.0f;
     constants.pixelcentercorrection[3] = 0.0f;
 
-    if (g_ActiveConfig.backend_info.bSupportsDepthClamp &&
-        !g_ActiveConfig.backend_info.bSupportsOversizedDepthRanges)
+    if (g_renderer->UseVertexDepthRange())
     {
       // Oversized depth ranges are handled in the vertex shader. We need to reverse
-      // the far value to get a reversed depth range mapping. This is necessary
-      // because the standard depth range equation pushes all depth values towards
-      // the back of the depth buffer where conventionally depth buffers have the
-      // least precision.
+      // the far value to use the reversed-Z trick.
       if (g_ActiveConfig.backend_info.bSupportsReversedDepthRange)
       {
-        if (fabs(xfmem.viewport.zRange) > 16777215.0f || fabs(xfmem.viewport.farZ) > 16777215.0f)
-        {
-          // For backends that support reversing the depth range we also support cases
-          // where the console also uses reversed depth with the same accuracy. We need
-          // to make sure the depth range is positive here and then reverse the depth in
-          // the backend viewport.
+        // Sometimes the console also tries to use the reversed-Z trick. We can only do
+        // that with the expected accuracy if the backend can reverse the depth range.
         constants.pixelcentercorrection[2] = fabs(xfmem.viewport.zRange) / 16777215.0f;
         if (xfmem.viewport.zRange < 0.0f)
           constants.pixelcentercorrection[3] = xfmem.viewport.farZ / 16777215.0f;
         else
           constants.pixelcentercorrection[3] = 1.0f - xfmem.viewport.farZ / 16777215.0f;
       }
-      }
       else
-      {
-        if (xfmem.viewport.zRange < 0.0f || xfmem.viewport.zRange > 16777215.0f ||
-            fabs(xfmem.viewport.farZ) > 16777215.0f)
       {
         // For backends that don't support reversing the depth range we can still render
-          // cases where the console uses reversed depth correctly. But we simply can't
-          // provide the same accuracy as the console.
+        // cases where the console uses the reversed-Z trick. But we simply can't provide
+        // the expected accuracy, which might result in z-fighting.
         constants.pixelcentercorrection[2] = xfmem.viewport.zRange / 16777215.0f;
         constants.pixelcentercorrection[3] = 1.0f - xfmem.viewport.farZ / 16777215.0f;
       }
     }
-    }
 
     dirty = true;
     // This is so implementation-dependent that we can't have it here.