Decomposition

decompose functions

The decompose functions allow you to grab certain data from an AbstractGeometry like a mesh or primitive and convert it to a requested type, if possible. They can also be used to convert an array of e.g. faces into a different face type directly. The default decomposition implemented by GeoemtryBasics are:

• decompose(::Type{<: Point}, source) which collects data from source using coordinates(source) and converts it to the given point type.
• decompose_normals([::Type{<: Vec},] source) = decompose([::Type{Normals{<: Vec}}},] source) which collects data with normals(source) and converts it to the given Vec type.
• decompose_uv([::Type{<: Vec},] source) = decompose([::Type{UV{<: Vec}}},] source) which collects data with texturecoordinates(source) and converts it to the given Vec type. This function also exists with UVW texture coordinates.
• decompose(::Type{<: AbstractFace}, source) which collects data with faces(source) and converts it to the given face type.

Extending decompose

For decompose to work there needs to be a conversion from some element type to some target type. GeometryBasics relies on GeometryBasics.convert_simplex(TargetType, value) for this. If you want to add new types to decompose, e.g. a new face type, you will need to add a method to that function.

Primitive decomposition

GeometryBasics defines an interface to decompose geometry primitives into vertex attributes and faces. The interface includes four functions:

• coordinates(primitive[, nvertices]) which produces the positions associated with the primitive
• faces(primitive[, nvertices]) which produces the faces which connect the vertex positions to a mesh
• normals(primitive[, nvertices]) which optionally provide normal vectors of the primitive
• texturecoordinates(primitive[, nvertices]) which optional provide texture coordinates (uv/uvw) of the primitive