Seeing Geometry
•Geometric descriptions are abstract, mathematical descriptions
•Rendering a geometric description makes it visible on the screen (or printer)
–done by sampling the geometry and creating pixel arrays (raster images)
•These images are not stored as part of the model. 
•Can’t usually work directly with individual pixels in geometry-based programs
–Elements’ geometric descriptions manipulated, then rendered
•
But doesn’t the screen just show pixels?

Yes

Geometric objects have to be rendered as pixels for display… but when you click on a part of an object, that whole description is ‘selected” and changed by subsequent operations.