When are tris used effectively?

#1

When should tris be used on a model? Where are they usually seen?

For example, this image of a popcorn container (from turbosquid) uses tris for the top half circles and the edge corners on the bottom. Is this use of tris appropriate for this kind of model?

Why are triangles added at the bottom corners?

#2

It’s just a way to terminate the edge loops to keep the polycount down. There are some more elegant ways to do it, but for something that’s not deforming, it’s not a problem.

#3

Thanks Meloncov, that makes sense. : ) What would be the alternative to using tris to end loops?

#4

Like this:

Or just connect the edge loops to the opposite side of the box. It’s not a game res model, so the extra polygons aren’t really a problem.