My question is that it is necessary to do map/unmap always when I want to get data from GPU.

My code is:

Me._ge3d.Device.ImmediateContext.CopyResource(BufferRectangles, Me.buf2)

Dim databox2 As SlimDX.DataBox = Me._ge3d.Device.ImmediateContext.MapSubresource(Me.buf2, 0, Me.buf2.Description.SizeInBytes, MapMode.Read, SlimDX.Direct3D11.MapFlags.None)

databox2.Data.Seek(0, IO.SeekOrigin.Begin)

If _arrayRectanglesMaximos Is Nothing Then
System.Array.Resize(_arrayRectanglesMaximos, CInt(MAXRECTANGLES))
End If

For i As Integer = 0 To Me._numRectanglesLeidos - 1

'Metemos los valores en el array...
Me._arrayRectanglesMaximos(i).X = databox2.Data.Read(Of Integer)()
Me._arrayRectanglesMaximos(i).Y = databox2.Data.Read(Of Integer)()

Me._arrayRectanglesMaximos(i).Width = databox2.Data.Read(Of Integer)()
Me._arrayRectanglesMaximos(i).Height = databox2.Data.Read(Of Integer)()
Next

Me._ge3d.Device.ImmediateContext.UnmapSubresource(Me.buf2, 0)

-----------------------------------------------

The last line is very slow (order of 30 mseg.) and I want to do it fast. Each frame I have to get this data from GPU and i do a copy of buffer. What ocurrs when I don`t have "unmap"??? Memory exception??

Thanks.

Because I use Compute Shader for calculating data from one image, and later I need this data for my program in .NET.

ReadRange o read from datastrem is fast, it is slow UNMAP the resource...