This is a fun program. From the Readme file:

 

Usage:

Import your obj+mtl scene, double-click to place the ivy root,
press "grow", and enjoy watching the ivy growing! If you want
to see the full geometry, press "birth". Use the export
function to save your ivy geometry as obj+mtl for usage in your
3d world. Please keep your scenes simple, since the growing
process slows down in complex scenes heavily. In case your ivy
is growing inside your objects, use the "flip normals" button
to flip the surface normals of your objects. You can customize
your ivy using the provided settings - tool-tips will help you
to understand the settings.

Camera controls:

rotate - left mouse button
track - left mouse button + control
dolly - right mouse button
orbit - left mouse button + shift