Calling SetDirtyRange() multiple times between calls to Draw()

Jun 1, 2010 at 11:42 AM

In a large vertex buffer that defines a triangleList, I occasionally update several triangles stored at non-contiguous locations in the buffer.  I am using this command to tell the buffer that the vertexData of three vertices belonging to one triangle have been updated:

vertexBuffer.SetDirtyRange(tLocationInVertexBuffer, 3);

For every group of triangles I try to modify with this method, half of them actually change and the rest remain unaffected.  

Is there any restriction about calling setDirtyRange() several times between Draw() calls to update multiple non-contiguous ranges in a buffer?