Hi,

On 25.10.2012 18:01, 刘先勇 wrote:

Dear Openflipper,

We have two questions. Hopefully we can get answers from you.

1). We can not use the following formula to get the right face area . 0.5* (((p1-p0) * (p2-p0)).norm()); For instance, the right value should be 0.145643363, but we got 0.0874207.

x y z 0.2649 0.1398 4.8136 0.7567 0.0491 4.8185 0.6181 -0.0791 4.2549 i j k 0.4918 -0.0907 0.0049 0.3532 -0.2189 -0.5587 0.0517467 0.27649934 -0.07562 0.002677721 0.076451885 0.005718 0.084848 0.145643

The area is defined via the cross product, but you use the scalar product. Changing your function to 0.5* (((p1-p0) % (p2-p0)).norm()); will fix it.

2). How to iterate vertices of a face in counterclockwise?

There is no fixed function for this, but you can simply walk around your vertex on your own:

Take one outgoing halfedge ohe;

To go counterclockwise to the next halfedge do: he = mesh.prev_halfedge_handle(he); he = opposite_halfedge_handle(he);

To get the vertices, Just use mesh.to_vertex_handle(he);

Best, Jan Möbius