Hello all.
I'm about to create an AI system for a 3d game engine and facing some issues.
the problem is that I have a terrain and want to implement a pathfinding system on it but I don't know exactly what to do. could anyone please tell me what the best way to do that is? Is it to use waypoints, to use a navigation mesh or to use the terrain's own nodes and triangles? and what things should I consider before any decision-making?

Probably, for such algorithm as A*, you have to convert your terrain to pathfinding graph firstly. For example, in my game i check the slope of every triangle of the terrain:

float slope = 1.0f - normal.y;

and if the slope is close to 1.0f, then i mark this part of terrain as unwalkable, otherwise convert it to the node in pathfinding graph.
In resulting graph just use A*.

When a character moves, game automatically sets y position(height) of a character based on the position of a triangle below it.