I have a flat bottom of a cup (just as an example) which consists of many triangles. I can select and delete the edges and replace the triangles with 1 ngon (which is flat and will remain flat).
So the question - is that useful for rendering/animation providing the number of the vertices remain the same? Or it is the opposite - no matter the ngon is flat is still better to keep the triangles?
as long has the surface is flat it does not really matter!
happy cl