Star wars is the only game to pass unsigned fixed shaded values (per vertex brightness) to the renderer. Originally we thought that the specular flag would turn on unsigned values since it's the only game to set specular with these polys, but this logic turned out to be incorrect. The JTAG interface seems to config the GPU to turn on this functionality. (Harry Tuttle)

Src/Graphics/IRender3D.h

@@ -16,13 +16,14 @@ public:
   virtual void EndFrame(void) = 0;
   virtual void UploadTextures(unsigned level, unsigned x, unsigned y, unsigned width, unsigned height) = 0;
   virtual void AttachMemory(const uint32_t *cullingRAMLoPtr, const uint32_t *cullingRAMHiPtr, const uint32_t *polyRAMPtr, const uint32_t *vromPtr, const uint16_t *textureRAMPtr) = 0;
-  virtual void SetStepping(int stepping) = 0;
-  virtual bool Init(unsigned xOffset, unsigned yOffset, unsigned xRes, unsigned yRes, unsigned totalXRes, unsigned totalYRes) = 0;
-  virtual void SetSunClamp(bool enable) = 0;
-  
-  virtual ~IRender3D()
-  {
-  }
+  virtual void SetStepping(int stepping) = 0;
+  virtual bool Init(unsigned xOffset, unsigned yOffset, unsigned xRes, unsigned yRes, unsigned totalXRes, unsigned totalYRes) = 0;
+  virtual void SetSunClamp(bool enable) = 0;
+  virtual void SetSignedShade(bool enable) = 0;
+
+  virtual ~IRender3D()
+  {
+  }
 };
 
 #endif  // INCLUDED_IRENDER3D_H

Src/Graphics/Legacy3D/Legacy3D.cpp

@@ -1298,12 +1298,16 @@ bool CLegacy3D::Init(unsigned xOffset, unsigned yOffset, unsigned xRes, unsigned
 }
 
 void CLegacy3D::SetSunClamp(bool enable)
-{
-}
-
-CLegacy3D::CLegacy3D(const Util::Config::Node &config)
-  : m_config(config)
-{ 
+{
+}
+
+void CLegacy3D::SetSignedShade(bool enable)
+{
+}
+
+CLegacy3D::CLegacy3D(const Util::Config::Node &config)
+  : m_config(config)
+{ 
   cullingRAMLo = NULL;
   cullingRAMHi = NULL;
   polyRAM = NULL;

Src/Graphics/Legacy3D/Legacy3D.h

@@ -334,13 +334,23 @@ public:
 	* Sets or unsets the clamped light model
 	*
 	* Parameters:
-	*		enable	Set clamp mode
-	*/
-	void SetSunClamp(bool enable);
-	 
-	/*
-	 * CLegacy3D(void):
-	 * ~CLegacy3D(void):
+	*		enable	Set clamp mode
+	*/
+	void SetSunClamp(bool enable);
+
+	/*
+	* SetSignedShade(bool enable);
+	*
+	* Sets the sign-ness of fixed shading value
+	*
+	* Parameters:
+	*		enable	Fixed shading is expressed as signed value
+	*/
+	void SetSignedShade(bool enable);
+
+	/*
+	 * CLegacy3D(void):
+	 * ~CLegacy3D(void):
 	 *
 	 * Parameters:
 	 *    config  Configuration object.

Src/Graphics/New3D/New3D.cpp

@@ -15,9 +15,9 @@
 namespace New3D {
 
 CNew3D::CNew3D(const Util::Config::Node &config, std::string gameName)
-  : m_r3dShader(config),
-    m_r3dScrollFog(config),
-	m_gameName(gameName)
+	: m_r3dShader(config),
+	  m_r3dScrollFog(config),
+	  m_gameName(gameName)
 {
 	m_cullingRAMLo	= nullptr;
 	m_cullingRAMHi	= nullptr;
@@ -25,6 +25,10 @@ CNew3D::CNew3D(const Util::Config::Node &config, std::string gameName)
 	m_vrom			= nullptr;
 	m_textureRAM	= nullptr;
 	m_sunClamp		= true;
+	m_shadeIsSigned = true;
+
+	// Fall-back mechanism for games with patched (not working) JTAG
+	if (m_gameName == "swtrilgy") m_shadeIsSigned = false;
 }
 
 CNew3D::~CNew3D()
@@ -1130,7 +1134,7 @@ void CNew3D::CacheModel(Model *m, const UINT32 *data)
 				float shade;
 				//==========
 
-				if (ph.SpecularEnabled()) {
+				if (!m_shadeIsSigned) {
 					shade = (ix & 0xFF) / 255.f;									// Star wars is the only game to use unsigned fixed shaded values. It's also the only game to set the specular flag on these polys
 				}
 				else {
@@ -1599,5 +1603,9 @@ void CNew3D::SetSunClamp(bool enable)
 	m_sunClamp = enable;
 }
 
-} // New3D
+void CNew3D::SetSignedShade(bool enable)
+{
+	m_shadeIsSigned = enable;
+}
 
+} // New3D

Src/Graphics/New3D/New3D.h

@@ -149,12 +149,22 @@ public:
 	* Parameters:
 	*		enable	Set clamp mode
 	*/
-	void SetSunClamp(bool enable);
-
-	/*
-	* CRender3D(config):
-	* ~CRender3D(void):
-	*
+	void SetSunClamp(bool enable);
+
+	/*
+	* SetSignedShade(bool enable);
+	*
+	* Sets the sign-ness of fixed shading value
+	*
+	* Parameters:
+	*		enable	Fixed shading is expressed as signed value
+	*/
+	void SetSignedShade(bool enable);
+
+	/*
+	* CRender3D(config):
+	* ~CRender3D(void):
+	*
 	* Constructor and destructor.
 	*
 	* Parameters:
@@ -200,13 +210,16 @@ private:
 	/*
 	* Data
 	*/
-
-	// Misc
-	std::string m_gameName;
-	bool m_sunClamp;
-
-	// Stepping
-	int		m_step;
+
+	// Misc
+	std::string m_gameName;
+
+	// GPU configuration
+	bool m_sunClamp;
+	bool m_shadeIsSigned;
+
+	// Stepping
+	int		m_step;
 	int		m_offset;			// offset to subtract for words 3 and higher of culling nodes
 	float	m_vertexFactor;		// fixed-point conversion factor for vertices
 

Src/Model3/Real3D.cpp

@@ -150,13 +150,15 @@ void CReal3D::LoadState(CBlockFile *SaveState)
  Rendering
 ******************************************************************************/
 
-static void UpdateRenderConfig(IRender3D *Render3D, uint64_t internalRenderConfig[])
-{
-  bool noSunClamp = (internalRenderConfig[0] & 0x800000) != 0 && (internalRenderConfig[1] & 0x400000) != 0;
-  Render3D->SetSunClamp(!noSunClamp);
-}
-
-void CReal3D::BeginVBlank(int statusCycles)
+static void UpdateRenderConfig(IRender3D *Render3D, uint64_t internalRenderConfig[])
+{
+  bool noSunClamp = (internalRenderConfig[0] & 0x800000) != 0 && (internalRenderConfig[1] & 0x400000) != 0;
+  bool shadeIsSigned = (internalRenderConfig[0] & 0x1) == 0;
+  Render3D->SetSunClamp(!noSunClamp);
+  Render3D->SetSignedShade(shadeIsSigned);
+}
+
+void CReal3D::BeginVBlank(int statusCycles)
 {
 #ifndef NEW_FRAME_TIMING
   // Calculate point at which status bit should change value.  Currently the same timing is used for both the status bit in ReadRegister