Introduction
============

The ``pyddg`` is a python library for **projective geometry**, **discrete differential geometry**, and its visualization in **blender**.
It provides

-  **datastructures** for discrete surfaces:
   
   -  Indexed face set
     
      -  conversion to and from obj
       
   -  Half-edge data structure
     
      -  subdivision
      -  Edge-flip algorithm to obtain Delaunay tessellation
       
   -  Nets
     
      -  smooth nets (parametrized curves and surfaces)
       
	 -  sampling of smooth nets
	 
      -  discrete nets (discrete curves and quadrilateral meshes)
       
-  a framework for **projective geometry** and subgeometries:
   
   -  projective subspaces
     
      -  homogeneous coordinates
      -  dualization
       
   -  quadrics
     
      -  projective and affine normalization
      -  parametrization (conversion to smooth net)
       
   -  Geometries and models
     
      -  Cayley-Klein geometries
      -  conversion of projective subspaces between different models of geometries
       
-  an interface to **blender**:
   
   -  blender bridge for nets and half-edge datastructure
     
-  an **update mechanism** for parameter dependent and interdepent objects (including corresponding objects in blender)