  The placement of vegetation plays a central role in the realism of virtual
scenes. We introduce procedural placement models (PPMs) for vegetation in urban
layouts. PPMs are environmentally sensitive to city geometry and allow
identifying plausible plant positions based on structural and functional zones
in an urban layout. PPMs can either be directly used by defining their
parameters or can be learned from satellite images and land register data.
Together with approaches for generating buildings and trees, this allows us to
populate urban landscapes with complex 3D vegetation. The effectiveness of our
framework is shown through examples of large-scale city scenes and close-ups of
individually grown tree models; we also validate it by a perceptual user study.
