add create vertex buffer for a triangle

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;
 }