Draw a rectangle with DX11

Question

I need to draw a simple rectangle (not a filled box) with directx 11.

I have found this code:

    const float x = 0.1;
    const float y = 0.1;
    const float height = 0.9;
    const float width = 0.9;
    
   VERTEX OurVertices[] =
    {
        { x, y, 0, col },
        { x + width, y, 0, col },
        { x, y + height, 0, col },
        { x + width, y, 0, col },
        { x + width, y + height, 0 , col },
        { x, y + height, 0, col }
    };

    static const XMVECTORF32 col = { 1.f, 2.f, 3.f, 4.f };

    // this is the function used to render a single frame
    void RenderFrameTest(void)
    {
        // float color[4] = { 0.0f, 0.2f, 0.4f, 1.0f };
        float color[4] = { 0.0f, 0.0f, 0.0f, 0.0f };
    
        // clear the back buffer to a deep blue
        devcon->ClearRenderTargetView(backbuffer, color);
    
        // select which vertex buffer to display
        UINT stride = sizeof(VERTEX);
        UINT offset = 0;
    
         devcon->IASetVertexBuffers(0, 1, &pVBuffer, &stride, &offset);
        // select which primtive type we are using
      //   draw the vertex buffer to the back buffer
        devcon->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_TRIANGLESTRIP);
        devcon->Draw(sizeof(OurVertices) / sizeof(VERTEX), 0);
      
        swapchain->Present(0, 0);
    
    }
    
    

   
    void DrawRectangle(float x, float y, float width, float height, XMVECTORF32 col)
    {
        D3D11_BUFFER_DESC bd;
        ZeroMemory(&bd, sizeof(bd));
        bd.Usage = D3D11_USAGE_DYNAMIC;
        bd.ByteWidth = sizeof(OurVertices);
        bd.BindFlags = D3D11_BIND_VERTEX_BUFFER;
        bd.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
        HRESULT val = dev->CreateBuffer(&bd, NULL, &pVBuffer);                   // create the buffer
        D3D11_MAPPED_SUBRESOURCE ms;
        val = devcon->Map(pVBuffer, NULL, D3D11_MAP_WRITE_DISCARD, NULL, &ms);   // map the buffer
        memcpy(ms.pData, OurVertices, sizeof(OurVertices));                      // copy the data
        devcon->Unmap(pVBuffer, NULL);
    }

but the result is not what I expected:

I suspect the problem is OurVertices array and "D3D11_PRIMITIVE_TOPOLOGY_TRIANGLESTRIP" but I don't have have experience with DirectX in general.

Can you help me please?

Answer 1

You have 6 vertices defined for a rectangle, which means you want to use TriangleList topology and not TriangleStrip topology.