GPU: Implement transparency mode

src/pse-sdl/sdl_interface.cpp

@@ -304,6 +304,7 @@ void SDLInterface::RenderDisplay()
     return;
 
   glViewport(0, 0, m_window_width, m_window_height - 20);
+  glDisable(GL_BLEND);
   glDisable(GL_CULL_FACE);
   glDisable(GL_DEPTH_TEST);
   glDisable(GL_SCISSOR_TEST);

src/pse/gpu.cpp

@@ -388,7 +388,6 @@ void GPU::WriteGP0(u32 value)
         m_GPUSTAT.texture_disable = (param & (UINT32_C(1) << 11)) != 0;
         m_texture_config.x_flip = (param & (UINT32_C(1) << 12)) != 0;
         m_texture_config.y_flip = (param & (UINT32_C(1) << 13)) != 0;
-        m_texture_config.SetColorMode(m_GPUSTAT.texture_color_mode);
         Log_DebugPrintf("Set draw mode %08X", param);
       }
       break;
@@ -749,18 +748,6 @@ void GPU::DispatchRenderCommand(RenderCommand rc, u32 num_vertices) {}
 
 void GPU::FlushRender() {}
 
-void GPU::TextureConfig::SetColorMode(TextureColorMode new_color_mode)
-{
-  if (new_color_mode == TextureColorMode::Reserved_Direct16Bit)
-    new_color_mode = TextureColorMode::Direct16Bit;
-
-  if (color_mode == new_color_mode)
-    return;
-
-  color_mode = new_color_mode;
-  page_changed = true;
-}
-
 void GPU::TextureConfig::SetFromPolygonTexcoord(u32 texcoord0, u32 texcoord1)
 {
   SetFromPaletteAttribute(Truncate16(texcoord0 >> 16));
@@ -778,11 +765,16 @@ void GPU::TextureConfig::SetFromPageAttribute(u16 value)
   if (page_attribute == value)
     return;
 
-  base_x = static_cast<s32>(ZeroExtend32(value & UINT16_C(0x0F)) * UINT32_C(64));
-  base_y = static_cast<s32>(ZeroExtend32((value >> 11) & UINT16_C(1)) * UINT32_C(512));
-  SetColorMode(static_cast<TextureColorMode>((value >> 7) & UINT16_C(0x03)));
   page_attribute = value;
   page_changed = true;
+
+  base_x = static_cast<s32>(ZeroExtend32(value & UINT16_C(0x0F)) * UINT32_C(64));
+  base_y = static_cast<s32>(ZeroExtend32((value >> 11) & UINT16_C(1)) * UINT32_C(512));
+  color_mode = (static_cast<TextureColorMode>((value >> 7) & UINT16_C(0x03)));
+  if (color_mode == TextureColorMode::Reserved_Direct16Bit)
+    color_mode = TextureColorMode::Direct16Bit;
+
+  transparency_mode = (static_cast<TransparencyMode>((value >> 5) & UINT16_C(0x03)));
 }
 
 void GPU::TextureConfig::SetFromPaletteAttribute(u16 value)

src/pse/gpu.h

@@ -110,6 +110,14 @@ protected:
     Reserved_Direct16Bit = 3
   };
 
+  enum class TransparencyMode : u8
+  {
+    HalfBackgroundPlusHalfForeground = 0,
+    BackgroundPlusForeground = 1,
+    BackgroundMinusForeground = 2,
+    BackgroundPlusQuarterForeground = 3
+  };
+
   union RenderCommand
   {
     u32 bits;
@@ -127,6 +135,7 @@ protected:
     // Helper functions.
     bool IsTextureEnabled() const { return (primitive != Primitive::Line && texture_enable); }
     bool IsTextureBlendingEnabled() const { return (IsTextureEnabled() && !texture_blend_disable); }
+    bool IsTransparencyEnabled() const { return transparency_enable; }
   };
 
   // TODO: Use BitField to do sign extending instead
@@ -181,7 +190,7 @@ protected:
     u32 bits;
     BitField<u32, u8, 0, 4> texture_page_x_base;
     BitField<u32, u8, 4, 1> texture_page_y_base;
-    BitField<u32, u8, 5, 2> semi_transparency;
+    BitField<u32, TransparencyMode, 5, 2> semi_transparency_mode;
     BitField<u32, TextureColorMode, 7, 2> texture_color_mode;
     BitField<u32, bool, 9, 1> dither_enable;
     BitField<u32, bool, 10, 1> draw_to_display_area;
@@ -221,14 +230,13 @@ protected:
     u16 page_attribute;          // from register in rectangle modes/vertex in polygon modes
     u16 palette_attribute;       // from vertex
     TextureColorMode color_mode; // from register/vertex in polygon modes
+    TransparencyMode transparency_mode;
 
     bool page_changed = false;
 
     bool IsPageChanged() const { return page_changed; }
     void ClearPageChangedFlag() { page_changed = false; }
 
-    void SetColorMode(TextureColorMode new_color_mode);
-
     void SetFromPolygonTexcoord(u32 texcoord0, u32 texcoord1);
     void SetFromRectangleTexcoord(u32 texcoord);
 

src/pse/gpu_hw_opengl.cpp

@@ -191,6 +191,36 @@ void GPU_HW_OpenGL::SetScissor()
   glScissor(x, y, width, height);
 }
 
+void GPU_HW_OpenGL::SetBlendState()
+{
+  struct BlendVars
+  {
+    GLenum src_factor;
+    GLenum func;
+    GLenum dst_factor;
+    float color;
+  };
+  static const std::array<BlendVars, 4> blend_vars = {{
+    {GL_CONSTANT_COLOR, GL_FUNC_ADD, GL_CONSTANT_COLOR, 0.5f}, // B/2 + F/2
+    {GL_ONE, GL_FUNC_ADD, GL_ONE, -1.0f},                      // B + F
+    {GL_ONE, GL_FUNC_REVERSE_SUBTRACT, GL_ONE, -1.0f},         // B - F
+    {GL_CONSTANT_COLOR, GL_FUNC_ADD, GL_ONE, 0.25f}            // B + F/4
+  }};
+
+  if (!m_batch_command.IsTransparencyEnabled())
+  {
+    glDisable(GL_BLEND);
+    return;
+  }
+
+  const BlendVars& vars = blend_vars[static_cast<u8>(m_texture_config.transparency_mode)];
+  glEnable(GL_BLEND);
+  glBlendFuncSeparate(vars.src_factor, vars.dst_factor, GL_ONE, GL_ZERO);
+  glBlendEquationSeparate(vars.func, GL_FUNC_ADD);
+  if (vars.color >= 0.0f)
+    glBlendColor(vars.color, vars.color, vars.color, 1.0f);
+}
+
 void GPU_HW_OpenGL::UpdateDisplay()
 {
   GPU_HW::UpdateDisplay();
@@ -322,6 +352,7 @@ void GPU_HW_OpenGL::FlushRender()
   SetProgram(m_batch_command.IsTextureEnabled(), m_batch_command.IsTextureBlendingEnabled());
   SetViewport();
   SetScissor();
+  SetBlendState();
 
   glBindFramebuffer(GL_FRAMEBUFFER, m_framebuffer_fbo_id);
   glBindVertexArray(m_vao_id);

src/pse/gpu_hw_opengl.h

@@ -40,6 +40,7 @@ private:
   void SetProgram(bool textured, bool blending);
   void SetViewport();
   void SetScissor();
+  void SetBlendState();
 
   std::unique_ptr<GL::Texture> m_framebuffer_texture;
   GLuint m_framebuffer_fbo_id = 0;