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How to: Create a Vertex Buffer

Vertex buffers contain per vertex data. This topic shows how to initialize a static vertex buffer, that is, a vertex buffer that does not change. For help initializing a non-static buffer, see the remarks section.

Ff476899.wedge(en-us,VS.85).gifTo initialize a static vertex buffer

  1. Define a structure that describes a vertex. For example, if your vertex data contains position data and color data, your structure would have one vector that describes the position and another that describes the color.
  2. Allocate memory (using malloc or new) for the structure that you defined in step one. Fill this buffer with the actual vertex data that describes your geometry.
  3. Create a buffer description by filling in a D3D11_BUFFER_DESC structure. Pass the D3D11_BIND_VERTEX_BUFFER flag to the BindFlags member and pass the size of the structure from step one to the ByteWidth member.
  4. Create a subresource data description by filling in a D3D11_SUBRESOURCE_DATA structure. The pSysMem member of the D3D11_SUBRESOURCE_DATA structure should point directly to the resource data created in step two.
  5. Call ID3D11Device::CreateBuffer while passing the D3D11_BUFFER_DESC structure, the D3D11_SUBRESOURCE_DATA structure, and the address of a pointer to the ID3D11Buffer interface to initialize.

The following code example demonstrates how to create a vertex buffer. This example assumes that g_pd3dDevice is a valid ID3D11Device object.



ID3D11Buffer*      g_pVertexBuffer;

// Define the data-type that
// describes a vertex.
struct SimpleVertexCombined
{
    XMFLOAT3 Pos;  
    XMFLOAT3 Col;  
};

// Supply the actual vertex data.
SimpleVertexCombined verticesCombo[] =
{
    XMFLOAT3( 0.0f, 0.5f, 0.5f ),
    XMFLOAT3( 0.0f, 0.0f, 0.5f ),
    XMFLOAT3( 0.5f, -0.5f, 0.5f ),
    XMFLOAT3( 0.5f, 0.0f, 0.0f ),
    XMFLOAT3( -0.5f, -0.5f, 0.5f ),
    XMFLOAT3( 0.0f, 0.5f, 0.0f ),
};

// Fill in a buffer description.
D3D11_BUFFER_DESC bufferDesc;
bufferDesc.Usage            = D3D11_USAGE_DEFAULT;
bufferDesc.ByteWidth        = sizeof( SimpleVertexCombined ) * 3;
bufferDesc.BindFlags        = D3D11_BIND_VERTEX_BUFFER;
bufferDesc.CPUAccessFlags   = 0;
bufferDesc.MiscFlags        = 0;

// Fill in the subresource data.
D3D11_SUBRESOURCE_DATA InitData;
InitData.pSysMem = verticesCombo;
InitData.SysMemPitch = 0;
InitData.SysMemSlicePitch = 0;

// Create the vertex buffer.
hr = g_pd3dDevice->CreateBuffer( &bufferDesc, &InitData, &g_pVertexBuffer );
    

Remarks

Here are some ways to initialize a vertex buffer that changes over time.

  1. Create a 2nd buffer with D3D11_USAGE_STAGING; fill the second buffer using ID3D11DeviceContext::Map, ID3D11DeviceContext::Unmap; use ID3D11DeviceContext::CopyResource to copy from the staging buffer to the default buffer.
  2. Use ID3D11DeviceContext::UpdateSubresource to copy data from memory.
  3. Create a buffer with D3D11_USAGE_DYNAMIC, and fill it with ID3D11DeviceContext::Map, ID3D11DeviceContext::Unmap (using the Discard and NoOverwrite flags appropriately).

#1 and #2 are useful for content that changes less than once per frame. In general, GPU reads will be fast and CPU updates will be slower.

#3 is useful for content that changes more than once per frame. In general, GPU reads will be slower, but CPU updates will be faster.

Related topics

Buffers

 

 

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