fix: dxDrawModel3D flickering issue

Client/game_sa/CModelInfoSA.h

@@ -46,6 +46,7 @@ static void* ARRAY_ModelInfo = *(void**)(0x403DA4 + 3);
 #define FUNC_CText_Get      0x6A0050
 #define FUNC_GetBoundingBox 0x4082F0
 
+#define FUNC_AddRef                0x4C4BA0
 #define FUNC_RemoveRef             0x4C4BB0
 #define FUNC_IsBoatModel           0x4c5a70
 #define FUNC_IsCarModel            0x4c5aa0
@@ -154,6 +155,9 @@ enum class eModelSpecialType : unsigned char
 class CBaseModelInfoSAInterface
 {
 public:
+    void AddRef() { ((void(__thiscall*)(CBaseModelInfoSAInterface*))FUNC_AddRef)(this); }
+    void RemoveRef() { ((void(__thiscall*)(CBaseModelInfoSAInterface*))FUNC_RemoveRef)(this); }
+
     CBaseModelInfo_SA_VTBL* VFTBL;  // +0
 
     unsigned long  ulHashKey;                 // +4   Generated by CKeyGen::GetUppercaseKey(char const *) called by CBaseModelInfo::SetModelName(char const *)

Client/game_sa/CRendererSA.cpp

@@ -32,25 +32,17 @@ void CRendererSA::RenderModel(CModelInfo* pModelInfo, const CMatrix& matrix, flo
     if (!pModelInfoSAInterface)
         return;
 
-    // Prevent GC from freeing RwObject during rendering
-    pModelInfo->ModelAddRef(NON_BLOCKING, "CRendererSA::RenderModel");
-
-    // Revalidate interface after AddRef
-    pModelInfoSAInterface = pModelInfo->GetInterface();
-    if (!pModelInfoSAInterface)
-    {
-        pModelInfo->RemoveRef();
-        return;
-    }
-
-    // Check and cache pRwObject
     RwObject* pRwObject = pModelInfoSAInterface->pRwObject;
     if (!pRwObject)
-    {
-        // Release reference before early return to prevent leak
-        pModelInfo->RemoveRef();
         return;
-    }
+
+    // Prevent GC from freeing RwObject/TXD during rendering by calling GTA's
+    // native CBaseModelInfo::AddRef/RemoveRef.  These manage usNumberOfRefs and
+    // texture dictionary refs without going through MTA's ref-counting (which
+    // triggers Remove() when m_dwReferences drops to 0, unloading the model
+    // every frame for dxDrawModel3D models with no persistent MTA-side reference
+    // -- causing visible flickering).
+    pModelInfoSAInterface->AddRef();
 
     RwFrame* pFrame = RpGetFrame(pRwObject);
 
@@ -61,7 +53,6 @@ void CRendererSA::RenderModel(CModelInfo* pModelInfo, const CMatrix& matrix, flo
     rwMatrix.pos = (RwV3d&)matrix.vPos;
     RwFrameTransform(pFrame, &rwMatrix, rwCOMBINEREPLACE);
 
-    // Ensure reference released on exception
     try
     {
         // Setup ambient light multiplier
@@ -83,9 +74,9 @@ void CRendererSA::RenderModel(CModelInfo* pModelInfo, const CMatrix& matrix, flo
     }
     catch (...)
     {
-        // Release reference on rendering exception
-        pModelInfo->RemoveRef();
+        pModelInfoSAInterface->RemoveRef();
         throw;
-    }  // Release reference - allow GC
-    pModelInfo->RemoveRef();
+    }
+
+    pModelInfoSAInterface->RemoveRef();
 }