what technique do you use for triangle on triangle collision detection?

You can use some geometric support. A triangle can be represented

by a set three points vertices(vertices), and each point contains two elements x,y. Each two points

form a section, and each section implies a line. You need to solve

these linear problems:

- Get two points and make a line. A line can be modeled by a vector and a point
- Get two lines and check if they cross each other, or have a common point.

You should solve a linear system - Telling if a given point belongs to a given section, whose line

already has passed (owned) that point.

Now two sections collide if their lines cross, and the common point belongs to

both the sections. Two triangles collide if and only if any section of one, collide

with any section of the other.