If you turn on backface culling, and only render the triangles that are facing the camera, then any convex object (like a cube) will render correctly (but you won't see the back-side, of course).

You can also split front- and back-faces into two separate primitives, and then sort all faces using a DAG, so that, no matter what direction you view the mesh from, the visible faces (depends on backface culling!) are drawn back-to-front. This works for convex shapes, and many, but not all, concave shapes (a "T" shape works, a "X" shape does not, because there are cycles in rendering order).

You can also sort each triangle, each time you draw. That works for most non-self-intersecting shapes. However, if two triangles cross each other, the only way to draw that right, transparently, is to split the triangles along the plane of intersection, and then draw.

Yes, this is complex.