Lecture Notes

Return to ARC550 home page

• Basic concepts of 3-D modeling
• Coordinate system-a global constant / Cartesian referencing system
• Primitive-in computer graphics, this is an image element, such as a square, a cube, a sphere, a torrus, or a pyramid for example, from which more complicated forms can be constructed. They can be thought of as forms whose basic characteristics are well defined.
• Basic organizational strategy
• I-node-the starting point of a line
• J-node-ending point of a line
• Points are stored in a database on the basis of each their x,y, and z coordinates.
• There can then be a second database that contains a list of lines in a given file. (These lines are defined by the points in the previously mentioned database). This forms the foundation of the relational database.
• Topology-a branch of math concerned with properties of geometric configurations (such as sets of points) that are unaltered by elastic deformations (such as stretching or twisting) that are homomorphisms.

• Basic discussion of menu items
• Availability of both modeling and drafting windows (3-D versus 2-D).
• One can cross-reference the other by copying and pasting.
• Copying from the modeling environment to the drafting environment causes the 3-D information to be dropped, thus flattening the model into a 2-D image.
• One can import various file types into Form· Z.
• .dwg’s from AutoCAD.
• Raster images (.jpg’s).
• Under the Edit menu:
• One can undo commands.
• This causes the contents of the database to be altered, therefore, commands such as zooming in or out, or panning cannot be undone, because such commands do not affect the database.
• One can "grab" an image.
• This copies data selected by the user that exists in VRAM, and saves it to RAM.
• One can choose to view ghosted objects.
• On the screen, the user views ghosted objects as being grayed. They are seen, but cannot be altered. So, the data which describes the ghosted object is in the database still, however, it is currently unalterable.
• By choosing "clear all ghosted" those objects that are ghosted are removed from the database.
• Heights.
• One can choose a set height that a 3-D object will take, or can graphically input or physically type in the desired height.
• One complication of interacting within a 3-D modeling environment is communicating to the computer where in the world (literally) the mouse is pointing.
• This can easily be done with specifying the reference plain on which the user is operating.
• View.
• This helps the user determine how he / she wants or view the model.
• One can choose angle; such as 30 degrees, front, side, or top for example.
• This can be very convenient in choosing the most helpful angle to interact with a model.