add index buffer

PracticeDx/WinMain.cpp

@@ -54,21 +54,28 @@ const Vertex vertices[] =
     { -0.5f, -0.5f, 0.0f, 0.0f, 1.0f },
 
     // left top
-    { 0.0f, 0.5f, 1.0f, 0.0f, 0.0f },
-    { -0.5f, -0.5f, 0.0f, 0.0f, 1.0f },
     { -0.3f, 0.3f, 0.0f, 1.0f, 0.0f },
 
-
     // right top
-    { 0.5f, -0.5f, 0.0f, 1.0f, 0.0f },
-    { 0.0f, 0.5f, 1.0f, 0.0f, 0.0f },
     { 0.3f, 0.3f, 0.0f, 0.0f, 1.0f },
 
     // center bottom
-    { 0.5f, -0.5f, 0.0f, 1.0f, 0.0f },
     { 0.0f, -0.8f, 1.0f, 0.0f, 0.0f },
-    { -0.5f, -0.5f, 0.0f, 0.0f, 1.0f },
+};
 
+// Define index buffer
+Microsoft::WRL::ComPtr<ID3D11Buffer>            pIndexBuffer;
+// create index buffer
+const unsigned short indices[] =
+{
+    // draw center
+    0, 1, 2,
+    // draw left top
+    0, 2, 3,
+    // draw right top
+    0, 4, 1,
+    // draw bottom
+    1, 5, 2,
 };
 
 // Define constant buffer
@@ -127,6 +134,26 @@ void DefineVertexBuffer()
     dev->CreateBuffer(&bd, &sd, &pVertexBuffer);
 }
 
+void DefineIndexBuffer()
+{
+    D3D11_BUFFER_DESC ibd = {};
+    ibd.BindFlags = D3D11_BIND_INDEX_BUFFER;
+    ibd.Usage = D3D11_USAGE_DEFAULT;
+    ibd.CPUAccessFlags = 0u;
+    ibd.MiscFlags = 0u;
+    ibd.ByteWidth = sizeof(indices);
+    ibd.StructureByteStride = sizeof(unsigned short);
+
+    D3D11_SUBRESOURCE_DATA isd = {};
+    isd.pSysMem = indices;
+
+    // Create index buffer
+    dev->CreateBuffer(&ibd, &isd, &pIndexBuffer);
+
+    // Bind index buffer to pipeline
+    devcon->IASetIndexBuffer(pIndexBuffer.Get(), DXGI_FORMAT_R16_UINT, 0u);
+}
+
 void DefineConstantBuffer(float angle)
 {
     cb =
@@ -195,13 +222,15 @@ void DrawPrimitive()
     devcon->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST);
 
     // Draw the triangle.
-    devcon->Draw((UINT)sizeof(vertices), 0u);
+    // devcon->Draw((UINT)sizeof(vertices), 0u);
+    devcon->DrawIndexed((UINT)std::size(indices), 0u, 0u);
 }
 
 void drawTriangle()
 {
     DefineShader();
     DefineVertexBuffer();
+    DefineIndexBuffer();
     DefineConstantBuffer(timer.Peek());
     DefineInputLayout();
     DrawPrimitive();