OGL: Check for GL_DEPTH_CLAMP support.

It's not available in OpenGL ES and officially it's not supported on OpenGL 3.0/3.1.

Fallback to old depth range code if there is no method to disable depth clipping.
It's more important to have correct clipping than to have accurate depth values.
Inaccurate depth values can be fixed by slow depth.

1 files changed, 25 insertions, 5 deletions

diff --git a/Source/Core/VideoBackends/OGL/Render.cpp b/Source/Core/VideoBackends/OGL/Render.cpp
index 692bf36e51..5af9407763 100644
--- a/Source/Core/VideoBackends/OGL/Render.cpp
+++ b/Source/Core/VideoBackends/OGL/Render.cpp
@@ -481,6 +481,9 @@ Renderer::Renderer()
   g_Config.backend_info.bSupportsBindingLayout =
       GLExtensions::Supports("GL_ARB_shading_language_420pack");
 
+  // Clip distance support is useless without a method to clamp the depth range
+  g_Config.backend_info.bSupportsDepthClamp = GLExtensions::Supports("GL_ARB_depth_clamp");
+
   g_ogl_config.bSupportsGLSLCache = GLExtensions::Supports("GL_ARB_get_program_binary");
   g_ogl_config.bSupportsGLPinnedMemory = GLExtensions::Supports("GL_AMD_pinned_memory");
   g_ogl_config.bSupportsGLSync = GLExtensions::Supports("GL_ARB_sync");
@@ -520,6 +523,9 @@ Renderer::Renderer()
     g_ogl_config.bSupportsGLSLCache = true;
     g_ogl_config.bSupportsGLSync = true;
 
+    // TODO: Implement support for GL_EXT_clip_cull_distance when there is an extension for depth clamping.
+    g_Config.backend_info.bSupportsDepthClamp = false;
+
     if (strstr(g_ogl_config.glsl_version, "3.0"))
     {
       g_ogl_config.eSupportedGLSLVersion = GLSLES_300;
@@ -669,7 +675,7 @@ Renderer::Renderer()
                                    g_ogl_config.gl_renderer, g_ogl_config.gl_version),
                   5000);
 
-  WARN_LOG(VIDEO, "Missing OGL Extensions: %s%s%s%s%s%s%s%s%s%s%s%s%s",
+  WARN_LOG(VIDEO, "Missing OGL Extensions: %s%s%s%s%s%s%s%s%s%s%s%s%s%s",
            g_ActiveConfig.backend_info.bSupportsDualSourceBlend ? "" : "DualSourceBlend ",
            g_ActiveConfig.backend_info.bSupportsPrimitiveRestart ? "" : "PrimitiveRestart ",
            g_ActiveConfig.backend_info.bSupportsEarlyZ ? "" : "EarlyZ ",
@@ -681,7 +687,8 @@ Renderer::Renderer()
            g_ActiveConfig.backend_info.bSupportsSSAA ? "" : "SSAA ",
            g_ActiveConfig.backend_info.bSupportsGSInstancing ? "" : "GSInstancing ",
            g_ActiveConfig.backend_info.bSupportsClipControl ? "" : "ClipControl ",
-           g_ogl_config.bSupportsCopySubImage ? "" : "CopyImageSubData ");
+           g_ogl_config.bSupportsCopySubImage ? "" : "CopyImageSubData ",
+           g_ActiveConfig.backend_info.bSupportsDepthClamp ? "" : "DepthClamp ");
 
   s_last_multisamples = g_ActiveConfig.iMultisamples;
   s_MSAASamples = s_last_multisamples;
@@ -724,8 +731,11 @@ Renderer::Renderer()
   glClearDepthf(1.0f);
   glEnable(GL_DEPTH_TEST);
   glDepthFunc(GL_LEQUAL);
-  glEnable(GL_CLIP_DISTANCE0);
-  glEnable(GL_DEPTH_CLAMP);
+  if (g_ActiveConfig.backend_info.bSupportsDepthClamp)
+  {
+    glEnable(GL_CLIP_DISTANCE0);
+    glEnable(GL_DEPTH_CLAMP);
+  }
 
   glPixelStorei(GL_UNPACK_ALIGNMENT, 4);  // 4-byte pixel alignment
 
@@ -1117,6 +1127,12 @@ void Renderer::SetViewport()
                           (float)scissorYOff);
   float Width = EFBToScaledXf(2.0f * xfmem.viewport.wd);
   float Height = EFBToScaledYf(-2.0f * xfmem.viewport.ht);
+  float GLNear = MathUtil::Clamp<float>(
+                     xfmem.viewport.farZ -
+                         MathUtil::Clamp<float>(xfmem.viewport.zRange, -16777216.0f, 16777216.0f),
+                     0.0f, 16777215.0f) /
+                 16777216.0f;
+  float GLFar = MathUtil::Clamp<float>(xfmem.viewport.farZ, 0.0f, 16777215.0f) / 16777216.0f;
   if (Width < 0)
   {
     X += Width;
@@ -1138,7 +1154,11 @@ void Renderer::SetViewport()
     auto iceilf = [](float f) { return static_cast<GLint>(ceilf(f)); };
     glViewport(iceilf(X), iceilf(Y), iceilf(Width), iceilf(Height));
   }
-  glDepthRangef(16777215.0f / 16777216.0f, 0.0f);
+
+  if (g_ActiveConfig.backend_info.bSupportsDepthClamp)
+    glDepthRangef(16777215.0f / 16777216.0f, 0.0f);
+  else
+    glDepthRangef(GLFar, GLNear);
 }
 
 void Renderer::ClearScreen(const EFBRectangle& rc, bool colorEnable, bool alphaEnable, bool zEnable,