Vertex data from a buffer

Question

I'm using a geometry shader to generate polygons for my voxel terrain (marching cubes). The data is output into a buffer using the method shown in the article I link to below.

http://msdn.microsoft.com/en-us/library/bb205122%28v=vs.85%29.aspx

Is there any way to somehow extract the vertex data from the buffer, sort of like the inverse operation of this?

struct Vertex
{
    float x, y, z;
    float tu, tv;
}

Vertex[] data = new[] // this is what I want to get
{
    ...
};

DataStream stream = new DataStream(bufferSize, true, true);
stream.Write(data);
stream.Position = 0;
buffer = new Buffer(device, stream, description);

To clarify, you want to get access to the generated vertex data on the CPU? — Nathan Reed
– Nathan Reed, Commented Jul 16, 2012 at 16:51
Yes, because I want to extract the positions so that I can generate a collision mesh. — jmegaffin
– jmegaffin, Commented Jul 16, 2012 at 17:35

Nathan Reed · Accepted Answer · 2012-07-16 18:15:18Z

1

You should be able to get CPU access to the data by using MapSubresource on the buffer (don't forget to unmap it when you're done). Be aware that this will cause a CPU/GPU sync, though: the CPU has to sit and wait for the GPU to finish all previous rendering before it can access the data. This is bad for performance if you're trying to do stuff in real-time.

answered Jul 16, 2012 at 18:15

Nathan Reed

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