The triangles you output from the GS are not indexed at all, since there are no indices. Instead you output one or more triangle strips. The vertices that you append to a TriangleStream form a strip according to the standard rules for a triangle strip topology. To mark the end of a strip, you call RestartStrip. If you want to just output a triangle list you can do so by appending 3 vertices, calling RestartStrip, and then repeating.
So in the case of your quad output from the GS, if you append all 4 verts and then call RestartStrip your 2 triangles will be (v0, v1, v2) and (v1, v2, v3), which means the winding order will be clockwise.
MJPMember Since 29 Mar 2007
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