Document how we can use CoordinateTransformations

[VEZY]

We are in the process of using the transformations from Meshes directly, but it means the package will not be compatible with CoordinateTransformations out-of-the-box anymore. Document how we can use such transformations instead.

The issue comes from the fact that we apply the transformation on the points directly, in the apply_transformation internal function:

function apply_transformation(transformation, ref_mesh)
    Meshes.SimpleMesh([transformation(p) for p in ref_mesh.vertices], Meshes.topology(ref_mesh))
end

The thing is CoordinateTransformations does not know how to be applied over Meshes.Point3, so we need to operate the transformation on the coordinates of the points instead, like so:

function apply_transformation(transformation, ref_mesh)
    Meshes.SimpleMesh([transformation(p.coords) for p in ref_mesh.vertices], Meshes.topology(ref_mesh))
end

But we can't apply the transformation from Meshes like so (don't know why, but the results are wrong, I don't have the time to investigate more).

So the solution is to keep applying the transformation on the points, but ask users to adapt a little bit the CoordinateTransformations transformation to manage Points. For example, to apply a rotation and a translation over a point, we can ask to wrap the transformation in a function and return a Meshes.Point like so:

mat = randn(4, 4)
transformation = x -> Meshes.Point3((Translation(@view mat[1:3, 4]) ∘ LinearMap(@view mat[1:3, 1:3]))(x.coords))

And then we can use the transformation directly on a Meshes point:

transformation(Meshes.Point3(1, 2, 3))

[VEZY]

Added doc to geometry for that

[VEZY]

Update: the geometry only accepts Transformations from TransformsBase / Meshes now, so we need to set a wrapper Transformation around the CoordinateTransformation.jl ones.