Organizing 3D Objects

• Objects are composed of polygons
  • We really like triangles for various reasons.
  • But we can deal with other shapes as well.
• We frequently store an object in a two or three level data structure
  • The lowest level is a vertex list
    • A vertex is at least the coordinates
    • But may have some other information attached to it.
    • We only store each vertex once
    • But they may be used MANY times
  • Sometimes we store an edge list
    • This is, at minimum, a pair of indexes into the vertex list.
    • But sometimes we might want more attributes as well.
    • We might skip this if we don't want to deal with edges.
  • The next level depends on the application
    • We could store a triangle list, especially if we are doing software hidden surface removal
    • We could store a polygon list
    • We could store a surface list
    • Each of these is a list of index values into the lower level.
• For this class, we will be using a very simple file format. .off files.
• Please see this page