Lecture Notes

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3/27/02

• To resize an object, select topo level to face, select a face (pre-pick) and select the move command and place the face in its new location.
• To do this Form· Z needs to know the original x,y,z coordinates and the D x, D y, D z. This creates a vector that will determine how far and in which direction to move (translate) the face: this operation uses addition.
• It is usually helpful to constrain the movement.
• Such as snaps, ortho, and constraining vertical movement.
• To change the color of a face of an object, select topo level to face, pre-pick the face, select the color desired in the surface style pallet, choose the color tool and click anywhere on the screen.
• Moving a single point associated with an object.
• Although possible, the result is a degenerate object; (Because of non-plainer faces).
• If one recalls the relational database where a table of objects refers to a table of faces that refers to a table of segments, which refers to a table of points.
• So if one point is moved, the user has changed one point in our table, however other tables remain unchanged.
• A properly formed polygon must fulfill two conditions:
  1. The defining points and segments must be coplanar
  2. The figure must be closed
• When degenerate objects are created, one will encounter several problems:
1. There will be irregular shadow casting associated with this object.
2. Boolean operations will not be possible.