Triangle - Why is it the basic building block for complex shapes I was recently learning about OpenGL and computer graphics development. I have a question regarding the usage of triangle as the basic building block, or basic shape to develop complex shapes. Is there a particular reason? Or just something that "stuck"?
Triangles are always flat, unlike a quad which can be made in a way that is bent / not all vertices on the same plane. 

If you were to interpolate say vertex normals across each scanline, on a 4-edge bent quad it will render with horizontal (scanline) artefacts. If you made that same bent quad out of triangles, it will render correctly as each triangle has a different normal slope. 

That's one reason why triangles are preferable for scanline rasterising