Function point_inside_triangle 

pub fn point_inside_triangle<T: Float + FloatOps<T> + NumberOps<T>, V: VecN<T> + NumberOps<T> + VecFloatOps<T>>(
    p: V,
    t1: V,
    t2: V,
    t3: V,
) -> bool

returns true if the point p is inside the triangle defined by t1-t2-t3