The reason the shape changes from 3D to 2D when you get to six triangles has to do with the number of degrees in an equilateral triangle. There are 60 degrees at each vertex of the triangle, so ...

Learn about properties of triangles with this BBC Bitesize Maths article. For students between the ages of 11 and 14. ... Arcs close arcs (annotation) Curved marks inside the vertex of a shape.

The vertex processing is done via 3 separate shaders (see code example): a vertex shader to set up the triangle ready for tessellating, a hull shader to generate the patch, ...