From 9a0c9a50ea56c98929d0189a524a741d9e7515d4 Mon Sep 17 00:00:00 2001
From: David Hackbarth <david@lyrebird-studio.com>
Date: Wed, 10 Sep 2025 11:27:40 +0200
Subject: [PATCH] add create vertex buffer for a triangle

---
 GDP/D3D9/D3D9.vcxproj         |  1 +
 GDP/D3D9/D3D9.vcxproj.filters |  3 +++
 GDP/D3D9/Direct3D.cpp         | 13 ++----------
 GDP/D3D9/Direct3D.h           |  2 +-
 GDP/D3D9/Mesh.cpp             | 39 +++++++++++++++++++++++++++++++++++
 GDP/D3D9/Vertex.h             | 14 +++++++++++++
 GDP/D3D9/main.cpp             | 10 ++++++++-
 7 files changed, 69 insertions(+), 13 deletions(-)
 create mode 100644 GDP/D3D9/Vertex.h

diff --git a/GDP/D3D9/D3D9.vcxproj b/GDP/D3D9/D3D9.vcxproj
index 8407012..c6a49c3 100644
--- a/GDP/D3D9/D3D9.vcxproj
+++ b/GDP/D3D9/D3D9.vcxproj
@@ -194,6 +194,7 @@
     <ClInclude Include="Mesh.h" />
     <ClInclude Include="Time.h" />
     <ClInclude Include="Utilities.h" />
+    <ClInclude Include="Vertex.h" />
     <ClInclude Include="Window.h" />
   </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
diff --git a/GDP/D3D9/D3D9.vcxproj.filters b/GDP/D3D9/D3D9.vcxproj.filters
index 8b4a2f3..a081ecc 100644
--- a/GDP/D3D9/D3D9.vcxproj.filters
+++ b/GDP/D3D9/D3D9.vcxproj.filters
@@ -68,5 +68,8 @@
     <ClInclude Include="Window.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="Vertex.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>
\ No newline at end of file
diff --git a/GDP/D3D9/Direct3D.cpp b/GDP/D3D9/Direct3D.cpp
index 479281c..a607d2a 100644
--- a/GDP/D3D9/Direct3D.cpp
+++ b/GDP/D3D9/Direct3D.cpp
@@ -1,6 +1,5 @@
 #include "Direct3D.h"
 #include "Utilities.h"
-#include <random>
 
 INT Direct3D::init(HWND hWnd, UINT width, UINT height, BOOL isFullscreen)
 {
@@ -49,23 +48,15 @@ INT Direct3D::init(HWND hWnd, UINT width, UINT height, BOOL isFullscreen)
 	return 0;
 }
 
-void Direct3D::beginScene()
+void Direct3D::beginScene(BYTE red, BYTE green, BYTE blue)
 {
 	_pD3DDevice->BeginScene(); // init a frame, after this call we are allowed to do draw calls
 
 	// change background color
-	static std::default_random_engine e;
-	static std::uniform_int_distribution<int> d(0, 255);
-
 	_pD3DDevice->Clear(
 		0, nullptr, // areas to clear, null -> everything
 		D3DCLEAR_TARGET, // what to clear, bitmask
-
-		// how to clean
-		//D3DCOLOR_XRGB(d(e), d(e), d(e)), //random color
-		//D3DCOLOR_XRGB(255, 0, 0), // red color
-		D3DCOLOR_XRGB(0, 0, 0), // black color
-		1.0f, 0xFFFFFFFF
+		D3DCOLOR_XRGB(red, green, blue), 1.0f, 0xFFFFFFFF // how to clean
 	);
 }
 
diff --git a/GDP/D3D9/Direct3D.h b/GDP/D3D9/Direct3D.h
index eee05a9..0bca579 100644
--- a/GDP/D3D9/Direct3D.h
+++ b/GDP/D3D9/Direct3D.h
@@ -7,7 +7,7 @@ class Direct3D
 {
 public:
 	INT init(HWND hWnd, UINT width, UINT height, BOOL isFullscreen);
-	void beginScene();
+	void beginScene(BYTE red, BYTE green, BYTE blue);
 	void endScene();
 	void deInit();
 
diff --git a/GDP/D3D9/Mesh.cpp b/GDP/D3D9/Mesh.cpp
index 443ec79..7b6e54d 100644
--- a/GDP/D3D9/Mesh.cpp
+++ b/GDP/D3D9/Mesh.cpp
@@ -1,5 +1,6 @@
 #include "Mesh.h"
 #include "Utilities.h"
+#include "Vertex.h"
 
 UINT Mesh::init(IDirect3DDevice9* pD3DDevice)
 {
@@ -20,6 +21,13 @@ void Mesh::update(FLOAT dt)
 
 void Mesh::render(IDirect3DDevice9* pD3DDevice)
 {
+    // 1. set mesh data
+    pD3DDevice->SetStreamSource(0, _pVertexBuffer, 0, _vertexStride);
+    pD3DDevice->SetFVF(FVF);
+
+    // 2. draw call
+    // vertex buffer only 
+    pD3DDevice->DrawPrimitive(D3DPT_TRIANGLELIST, 0, _vertexCount / 3); 
 }
 
 void Mesh::deInit()
@@ -30,6 +38,37 @@ void Mesh::deInit()
 
 UINT Mesh::createVertexBuffer(IDirect3DDevice9* pD3DDevice)
 {
+    // 1. define mesh parameters
+    _vertexCount = 3;
+    _vertexStride = sizeof(Vertex);
+
+    // 2. create vertex buffer object WITHOUT data
+    HRESULT hr = pD3DDevice->CreateVertexBuffer(
+        _vertexCount * _vertexStride, // vertex buffer size in bytes
+        D3DUSAGE_WRITEONLY, // how to access the buffer
+        FVF, // FVF - Flexible Vertex Format
+        D3DPOOL_MANAGED, // video memory management
+        &_pVertexBuffer, // vertex buffer object
+        nullptr // not used anymore
+    );
+    CheckFailed(hr, 300);
+
+    // 3. set vertex data
+    Vertex* pVertices = nullptr;
+
+    hr = _pVertexBuffer->Lock(0, 0, reinterpret_cast<void**>(&pVertices), 0); // transfer vertex buffer from video memory to cpu memory
+    CheckFailed(hr, 310);
+
+    // fill vertex buffer with data
+    pVertices[0] = Vertex(0.0f, 0.5f, 0.0f);
+    pVertices[1] = Vertex(0.5f, -0.5f, 0.0f);
+    pVertices[2] = Vertex(-0.5f, -0.5f, 0.0f);
+
+    hr = _pVertexBuffer->Unlock(); // transfer vertex buffer back from cpu memory to video memory
+    CheckFailed(hr, 320);
+
+    pVertices = nullptr;
+
     return 0;
 }
 
diff --git a/GDP/D3D9/Vertex.h b/GDP/D3D9/Vertex.h
new file mode 100644
index 0000000..2b87067
--- /dev/null
+++ b/GDP/D3D9/Vertex.h
@@ -0,0 +1,14 @@
+#pragma once
+#include <d3d9.h>
+
+#define FVF D3DFVF_XYZ
+
+struct Vertex
+{
+	FLOAT x;
+	FLOAT y;
+	FLOAT z;
+
+	Vertex() : x(0.0f), y(0.0f), z(0.0f) {}
+	Vertex(FLOAT _x, FLOAT _y, FLOAT _z) : x(_x), y(_y), z(_z) {}
+};
\ No newline at end of file
diff --git a/GDP/D3D9/main.cpp b/GDP/D3D9/main.cpp
index cc20ea5..e94cea6 100644
--- a/GDP/D3D9/main.cpp
+++ b/GDP/D3D9/main.cpp
@@ -1,4 +1,5 @@
 #include <Windows.h>
+#include <random>
 #include "Window.h"
 #include "Direct3D.h"
 #include "Mesh.h"
@@ -19,6 +20,9 @@ int WINAPI WinMain(
 	const UINT width = 640;
 	const UINT height = 480;
 	const BOOL isFullscreen = FALSE;
+	const BYTE red = 255;
+	const BYTE green = 255;
+	const BYTE blue = 255;
 
 	UINT error = 0; // error code for identifying errors
 
@@ -67,7 +71,11 @@ int WINAPI WinMain(
 		light.update(time.getDeltaTime());
 
 		// 8.2. render objects
-		d3d.beginScene();
+		static std::default_random_engine e;
+		static std::uniform_int_distribution<int> d(0, 255);
+
+		//d3d.beginScene(d(e), d(e), d(e)); //random color
+		d3d.beginScene(red, green, blue);
 
 		light.render(d3d.getDevice());
 		material.render(d3d.getDevice());