   Does drawindexedprimitive support D3DPT_TRIANGLESTRIP and D3DPT_TRIANGLEFAN?
  I think strip and fan give the definition of triangle in a vertex buffer.so index do not need. right?   
  The only type you can't used as indexed is a point list. You can still get benifits from using an indexed strip or fan, since you can share vertices.   ;  I think if you use strip or fan, you already define triangle with shared vertices.that is , fan and strip is similar to index. it define triangle according to vertex list. Could you give me a example that demonstrate triangles be defined by fan/strip and index together? thanks;  A regular grid. You have 1 long strip for each row, and you link 2 rows by adding degenerated tris. So, for this setup :0   1   2   34   5   6   78   9   10  11you have the indices0, 4, 1, 5, 2, 6, 3, 7, 7, 11, 10, 6, 9, 5, 8, 4You can't do that without using indices, since you'd have to add vertices.oh, and DirectX specific questions should go in the DirectX forum.   