Roman Reiner <lim### [at] gmxde> wrote:
> "kiwon" <nomail@nomail> wrote:
> > If I put *inside_vector y* (because the surface's average normal direction is y

> That's not how inside_vector works.

> It simply defines the specified point to be *inside* the object, thus
> determining its inside and outside.

  Nope. inside_vector defines a *direction*, not a point.

  When determining if a point is inside the mesh or not, a ray will be
shot in that specified direction from that point, and the number of
intersections with the mesh counted. (If the count is odd, then the point
is determined to be inside.)

  For closed meshes in theory there's little significance on which direction
you choose. Basically any direction would work equally well. There are certain
pathological circumstances where the chosen direction becomes crucial, though.
For example, if you have a triange that's exactly on the xy plane, choosing
an inside_vector x (or any other vector that's on the xy plane) can cause
the insideness calculations to fail for points on that plane. While this is
quite unlikely to happen and show visible effects, in theory it can happen.
That's why you should try to choose a direction that is not tangential to
any of the triangles, if possible.

-- 
                                                          - Warp

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