Lecture Notes

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4/24/02

• Glass
• Glass has an overwhelming set of options associated with this surface style.
• Reflectivity options:
• Ambient, diffuse specular
• Overall reflectivity; transmission of light through the surface style.
• Roughness-begins to address various qualities of the surface of the glass.
• Transparency options:
• Is set to none as the current default
• There are several settings the user can define
• Simple, center edge (more transparent in the center), and eroded are examples.
• Symbols
• The symbol toolbar contains four tools
• Symbol create, place, edit, and explode
• By including symbols in a model, another table is introduced to the database, including an ID tag of the symbol, the name of the symbol, and the local origin.
• This row of data creates one instance which represents the insertion of one symbol.
• The local origin is a single point related to a symbol which represents where the symbol will be inserted on the current reference plane.
• Scaling symbols.
• Most offices lock symbols so they cannot be scaled.  If this is not done, through manipulation, one may produce an object which is not a real world object.  This is a problem since symbols are usually very specific to the object which they are to represent.
• Creating symbols
• Select the objects that are to be included, select the symbol create tool, and click on the screen.  The point clicked on the screen will be the local origin of the symbol, which in turn dictates where the symbol is constructed.
• The instance is now linked to the definition, which equals all the points, faces, ect. which create the symbol.
• If this symbol definition is changed, all the inserted symbols are changed.
• A note about symbol libraries.
• When a new library is created, place it where it should exist on secondary memory.  The file extension will be .zlb.
• While a model may have links to various libraries saved in the model itself, the actual symbol definitions are another file all together called the library.
• After a library is loaded into a model, the user can view the various symbols under the symbol palate, as a series of thumbnails.
• Trees
• Trees are perhaps the most interesting library included.
• They are actually photographs applied to two perpendicular intersecting planes which are alpha channels.