Computing vanishing lines ground plane Properties I is intersection of horizontal plane through C with image plane Compute I from two sets of parallel lines on ground plane All points at same height as c project to points higher than c project above I Provides way of comparing height of objects in the scene
Computing vanishing lines Properties • l is intersection of horizontal plane through C with image plane • Compute l from two sets of parallel lines on ground plane • All points at same height as C project to l – points higher than C project above l • Provides way of comparing height of objects in the scene ground plane l C
Fun with vanishing points Illusions Terra Sttaraneae1997 shepard
Fun with vanishing points
Tour into the Picture"(SIGGRAPH'97) Create a 3d theatre stage"of five billboards 芈非 Specify foreground objects through bounding polygons 非 Use camera transformations to navigate through the scene
“Tour into the Picture” (SIGGRAPH ’97) Create a 3D “theatre stage” of five billboards Specify foreground objects through bounding polygons Use camera transformations to navigate through the scene
The idea Many scenes(especially paintings), can be represented as an axis-aligned box volume (i.e. a stage Key assumptions All walls of volume are orthogonal Camera view plane is parallel to back of volume Camera up is normal to volume bottom How many vanishing points does the box have? Three, but two at infinity Ceiling Single-point perspective Left wall Rear wall Right wall Can use the vanishing point to fit the box to the particular Floor Scene
The idea Many scenes (especially paintings), can be represented as an axis-aligned box volume (i.e. a stage) Key assumptions: • All walls of volume are orthogonal • Camera view plane is parallel to back of volume • Camera up is normal to volume bottom How many vanishing points does the box have? • Three, but two at infinity • Single-point perspective Can use the vanishing point to fit the box to the particular Scene!