facing3d subsets an object by converting it to a triangle mesh,
then subsetting to those triangles that are counterclockwise
front = TRUE) when projected into a plane.
projectDown computes a projection that “looks down” the specified direction.
facing3d(obj, up = c(0, 0, 1), P = projectDown(up), front = TRUE, strict = TRUE) projectDown(up)
An object that can be converted to a triangular mesh object.
The direction that is to be considered “up”. It may be either a 3 vector in Euclidean coordinates or a 4 vector in homogeneous coordinates.
The projection to use for draping, a 4x4 matrix. See
the returned subset will be those triangles whose upper side
up or use an
arbitrary projection for different subsets.
facing3d returns a mesh object made of those triangles which face in the
projectDown computes a 4x4 matrix. The first two
asEuclidean(x %*% projectDown(up))
give a projection of
x from above into a plane, where
up determines which direction is taken to be “up”.