useful Blender snippets

blender_snippets.py

def stereographic_project(obj):
    """
    Given a 2D xy plane, project it onto a 1 m sphere centered at the origin
    
    A point source of light placed at the top of this sphere (z = 1 m)
    will then cast a shadow that looks the same as the original plane
    """
    for vert in obj.data.vertices:
        x = vert.co.x
        y = vert.co.y
        denom = (x*x + y*y + 1.0)
        vert.co.x = 2.0 * x / denom
        vert.co.y = 2.0 * y / denom
        vert.co.z = (x*x + y*y - 1.0) / denom