Reporting Multiple Vertex Stream Capability
A driver reports the ability to support multiple vertex streams by setting the value of the MaxStreams field of the D3DCAPS8 structure. A driver that supports multiple vertex streams should specify a value greater than one. A DX8 level driver that does not support multiple vertex streams should set MaxStreams to one. No DX8 level driver should specify a value of zero for this field. The driver should also set the MaxStreamStride field to the maximum supported stride (in bytes) between vertex elements in a vertex stream.