So. The situation is that I am using OrthoGraphics and I am trying to call DrawIndexedPrimitive() in order to draw 4 triangles. The 4 triangles are actually 2 rectangles. The 2 rectangles have different coordinate.
Part of codes:
Result: It only drew the first 6 indices. (I did an experiment to prove this statement. I set the alpha to 128 so if it drew the same object at the same position twice, it will not be transparent. But it is still transparent which means it only drew it once, which means it only drew the first 6 indices.)
I can use two calls to achieve it. Like this: