Batch draw calls in Underworld

premake5.lua

@@ -47,7 +47,7 @@ project "TRAE-menu-hook"
         targetname "TRAE-Menu-Hook"
 
     filter "platforms:TR8"
-        defines { "TR8" }
+        defines { "TR8", "BATCH_DRAW_CALLS" }
         targetname "TR8-Menu-Hook"
 
 -- Tests

src/Hook.cpp

@@ -8,6 +8,7 @@
 #include "game/Game.h"
 #include "render/Font.h"
 #include "game/GameLoop.h"
+#include "render/DrawBatcher.h"
 
 // Modules
 #include "modules/MainMenu.h"
@@ -99,6 +100,10 @@ void Hook::OnFrame()
 	{
 		mod->OnFrame();
 	}
+
+#ifdef BATCH_DRAW_CALLS
+	DrawBatcher::GetInstance()->Flush();
+#endif
 }
 
 void Hook::OnLoop()

src/render/Draw.cpp

@@ -93,6 +93,13 @@ inline void TransformToLineVertex(LINEVERTEX* v, cdc::Vector3* vec)
 #endif
 }
 
+#ifndef BATCH_DRAW_CALLS
+inline void DrawTriangles(DRAWVERTEX* verts, int numtris)
+{
+	DRAW_DrawTriangles(2, 0, verts, numtris);
+}
+#endif
+
 void DrawTriangle(cdc::Vector3* v0, cdc::Vector3* v1, cdc::Vector3* v2, int color)
 {
 	DRAWVERTEX verts[3];
@@ -105,7 +112,7 @@ void DrawTriangle(cdc::Vector3* v0, cdc::Vector3* v1, cdc::Vector3* v2, int colo
 	verts[1].color = color;
 	verts[2].color = color;
 
-	DRAW_DrawTriangles(2, 0, verts, 1);
+	DrawTriangles(verts, 1);
 }
 
 void DrawPlane(cdc::Vector3* v0, cdc::Vector3* v1, int color)
@@ -129,7 +136,7 @@ void DrawPlane(cdc::Vector3* v0, cdc::Vector3* v1, int color)
 	verts[4].color = color;
 	verts[5].color = color;
 
-	DRAW_DrawTriangles(2, 0, verts, 2);
+	DrawTriangles(verts, 2);
 }
 
 void DrawLine(cdc::Vector3* v0, cdc::Vector3* v1, int color)

src/render/Draw.h

@@ -45,6 +45,8 @@ void DRAW_DrawLines(LINEVERTEX* verts, int numlines);
 void TransformToDrawVertex(DRAWVERTEX* v, cdc::Vector3* vec);
 void TransformToLineVertex(LINEVERTEX* v, cdc::Vector3* vec);
 
+void DrawTriangles(DRAWVERTEX* verts, int numtris);
+
 void DrawTriangle(cdc::Vector3* v0, cdc::Vector3* v1, cdc::Vector3* v2, int color);
 void DrawPlane(cdc::Vector3* v0, cdc::Vector3* v1, int color);
 void DrawLine(cdc::Vector3* v0, cdc::Vector3* v1, int color);

src/render/DrawBatcher.cpp

@@ -0,0 +1,55 @@
+#include "DrawBatcher.h"
+
+DrawBatcher* DrawBatcher::s_batcher = nullptr;
+
+DrawBatcher::DrawBatcher() : m_vertices()
+{
+	m_vertices.reserve(0x2000);
+}
+
+void DrawBatcher::DrawTriangles(DRAWVERTEX* verts, int numtris) noexcept
+{
+	auto numVerts = numtris * 3;
+
+	// Prevent allocations
+	if (m_vertices.size() + numVerts >= m_vertices.capacity())
+	{
+		Flush();
+	}
+
+	// Add to batch
+	for (int i = 0; i < numVerts; i++)
+	{
+		m_vertices.push_back(verts[i]);
+	}
+}
+
+void DrawBatcher::Flush() noexcept
+{
+	if (m_vertices.size() > 0)
+	{
+		DRAW_DrawTriangles(2, 0, m_vertices.data(), m_vertices.size() / 3);
+
+		m_vertices.clear();
+	}
+}
+
+DrawBatcher* DrawBatcher::GetInstance()
+{
+	// Since this is hot code which is called a lot during a frame
+	// there's a manual singleton here instead of a C++11 standard one
+	// which uses thread local storage
+	if (s_batcher == nullptr)
+	{
+		s_batcher = new DrawBatcher();
+	}
+
+	return s_batcher;
+}
+
+#ifdef BATCH_DRAW_CALLS
+void DrawTriangles(DRAWVERTEX* verts, int numtris)
+{
+	DrawBatcher::GetInstance()->DrawTriangles(verts, numtris);
+}
+#endif

src/render/DrawBatcher.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include <vector>
+
+#include "Draw.h"
+
+// Batcher for DRAW_ calls to limit the amount of draw calls sent to the GPU
+class DrawBatcher
+{
+private:
+	std::vector<DRAWVERTEX> m_vertices;
+
+	static DrawBatcher* s_batcher;
+
+public:
+	DrawBatcher();
+
+	void DrawTriangles(DRAWVERTEX* verts, int numtris) noexcept;
+	void Flush() noexcept;
+
+	static DrawBatcher* GetInstance();
+};