add basic docs for bounding boxes

Author: ffreyer

docs/make.jl

@@ -13,8 +13,9 @@ makedocs(format=Documenter.HTML(prettyurls=get(ENV, "CI", "false") == "true"),
                 "polygons.md",
                 "meshes.md",
                 "decomposition.md",
+                "boundingboxes.md",
                 "static_array_types.md",
-                "api.md"
+                "api.md",
                ],
          modules=[GeometryBasics])
 

docs/src/boundingboxes.md

@@ -0,0 +1,31 @@
+# Bounding Boxes
+
+You can generate an axis aligned bounding box for any `AbstractGeometry` by calling `Rect(geom)`.
+Depending on the object this will either rely on `coordinates(geom)` or a specialized method.
+You can also create a bounding box of set dimension or type by adding the related parameters.
+
+
+```@repl
+using GeometryBasics
+
+s = Circle(Point2f(0), 1f0)
+Rect(s) # specialized, exact bounding box
+Rect3(s)
+Rect3d(s)
+RectT{Float64}(s)
+Rect(GeometryBasics.mesh(s)) # using generated coordinates in mesh
+```
+
+## Extending
+
+If you want to add a specialized bounding box method you should implement `Rect{N, T}(geom) = ...`.
+All other methods funnel into that one, defaulting to the same `N, T` that the given `AbstractGeometry{N, T}` has.
+GeometryBasics allows the user given dimension `N` to be smaller or equal to that of the geometry.
+This is checked with `GeometryBasics.bbox_dim_check(user_dim, geom_dim)` which you may reuse.
+
+```@example
+function Rect{N, T}(a::HyperSphere{N2}) where {N, N2, T}
+    bbox_dim_check(N, N2)
+    return Rect{N, T}(minimum(a), widths(a))
+end
+```

src/boundingboxes.jl

@@ -60,9 +60,9 @@ function Rect{N, T}(a::Pyramid) where {N, T}
     return Rect{N, T}(m .- Vec{3,T}(w / T(2), w / T(2), 0), Vec{3,T}(w, w, h))
 end
 
-function Rect{N, T}(a::HyperSphere) where {N, T}
-    mini, maxi = extrema(a)
-    return Rect{N, T}(mini, maxi .- mini)
+function Rect{N, T}(a::HyperSphere{N2}) where {N, N2, T}
+    bbox_dim_check(N, N2)
+    return Rect{N, T}(minimum(a), widths(a))
 end
 
 # TODO: exact implementation that doesn't rely on coordinates