Generate a two-dimensional Dirichlet distribution of points within a triangle.

Input parameters:

1. N → Number of points to generate.
2. Tr → Triangle to cover with random points.
3. A1 → First Dirichlet alpha parameter.
4. A2 → Second Dirichlet alpha parameter.
5. A3 → Third Dirichlet alpha parameter.
6. Rn → Random engine used for distribution.

Output parameters:

1. Pt → Pseudo-random point cloud.