CIS881
Labs

This quarter, the labs will be demoed to the grader, not electronically submitted. I will make a sign-up sheet available for lab grading.

Some skeleton code will be provided which can be modified to do the labs. You will not be given sample labs; you are expected to design and implement your own lab.

You will have to demo your lab to the grader in order to have it evaluated.

Labs count for 30% of the final grade.

Contents:

• Lab 1 - Finalized
• Lab 2 - Finalized
• Lab 3 - Finalized

solids of revolution

The user should draw an open or closed curve. The curve is drawn relative to an axis in the display image; you can use either a default axis or a user-specified one). The user should be able to set the number of slices. Optional extension: check for overlap of contour and axis of revolution and issue a warning to the user.

extrusion

The user should draw one open or closed wire and be able to set the z-depth of the extrusion. the wire should be considered to lie in the x-y plane and the extrusion to occur in the z direction. Optional extension: you can generalize this to include a user-specified extrusion direction. Optional extension: you can generate multiple extruded wires.

sweep operators

User input of an open or closed generator wire and an open or closed trajectory wire. Consider the generator wire to lie in the x-y plane. Consider the trajectory wire to lie in the y-z plane.

output ASCII vertex-face file

Use counterclockwise face definitions and use the following format:

k2
    #-of-vertices=n #-of-faces=m
    x1 y1 z1
    x2 y2 z2
    ...
    xn yn zn
    #-of-vertices-in-first-face=k1 v11 v12 ... v1k1
    #-of-vertices-in-second-face=k2 v21 v22 ... v2k2
    ....
    #-of-vertices-in-mth-face=km vm1 vm2 ... vmkm

For example, a cube looks like:

    8 6
    -1  1  1
     1  1  1
     1 -1  1
    -1 -1  1
    -1  1 -1
     1  1 -1
     1 -1 -1
    -1 -1 -1
    4 3 2 1 0
    4 4 5 6 7
    4 5 4 0 1
    4 6 5 1 2
    4 7 6 2 3
    4 4 7 3 0

Extra Credit:

• Some useful collection of the extensions, error checking, noted above or other such features that you come up with (up to 10%)
• Lofting - loft a surface between multiple countours (10%)

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Lab2
Basic Curve Technology
5%; Be ready to demo May 10
Almost Finalized

Implement the following curve generation procedures in your Lab 1. Allow the user to select one of the techniques and generate a new wire from an existing wire by selecting the number of points (on a slider) and a curve generation technique (radio buttons).
• Blended Parabolas
• Catmull-Rom spline
• Bezier curve - one curve for all the points
• Cubic B-spline with uniform knot vector

These curves would then be used in your existing solids of revolution, extrusion and sweep operations.

Allow the user to generate a curve, go back and edit a point on the control wire, and then regenerate a new curve replacing the original curve.

Extra credit will be assigned for doing the more involved items or more of the simpler ones. (Extra credit percentage is the maximum given and usually requires supportive interface.)

• (5% each) Implement some of the following types of curve formulations (notice that some of these require a more extensive user interface):
  • Composite Hermite
  • cubic Bezier enforcing C¹ continuity at juntions (by repositioning control points)
  • rational Bezier
  • arbitrary order B-spline with arbitrary knot vector
  • NURBS
• (5%) Provide various options to handle boundary conditions for open Catmull-Romm splines,
• (5%) When lofting or sweeping between curves, allow the user to specify translation and rotation of the curves in space,
• (5%) Provide the ability for the user to specify duplicity of vertices in Bezier and B-spline curves (e.g., double, triple vertices),
• (5%) Allow editing the control points while the curve the simultaneously updated; optimize so that the entire curve does not have to be redrawn is local control is in effect,
• (5%,10%) Parameterize curves by arc length either brute force or numerically.

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Lab3
Full Project
20%; To be ready for demoing by noon, Wednesday, June 2nd
Finalized

Design and write a data generation program which uses surfaces in the spirit of solids of revolution, but uses multiple wires around the object to define control points of a surface which is closed in one direction and open in the other direction (i.e., topologically cylindrical). Allow the user to specify number of wires around the object and the resolution of the polygonization in u and v directions. Do the following surface types:
• Bezier surface enforcing G1 continuity in the closed direction
• Cubic B-spline surface - use uniform knot vector

You must generate .det objects as final output by polygonizing the surfaces using equally spaced u,v coordinates.

You will be graded on the design of the user interface and the generation power of your program.

To receive an A on the project, you will have to enhance the basic functionality in some interesting and/or significant manner. For example, choose two out of the following list:

• Recursively subdivide the surfaces using a test for planarity as the termination criteria,
• Reparameterize by arclength (you can use a brute force approach) prior to polygonization,
• Close the surface in the other direction enforcing G1 continuity constraints
• Use trim curves to trim the surface

You can choose to do something else that interests you as long as the complexity is comparable to the basic lab and you clear it with me first. Such as:

• trimmed NURBS surfaces with appropriate user interface to set knot values and weights,

I would like examples of interesting objects that I can put up on the class web site.

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syllabus
Last updated 5/17/99