Please, help me understand, how to detect: lies the point in triangle or not? I know, that this algorithm called as “barycentric” (“barycentric intersection”). As answer, give me a very small example please (more precisely, part of this example, when we detecting the point position) and just small math information.

If this topic had never been in this forum, I think it would be interesting.

P.S.
Please, don`t give me a useless answers or references.

The point is in the polygon plane?
Then, if the point is behind all edge planes (or in front depending how you turn the normals) then it’s in the polygon. The edge planes are easy to calculate with two vertices and the polygon normal.