CSE784
Labs

The lab specifications are tentative at this point and will be finalized as the quarter progresses. The 'Not finalized' label will be changed to 'finalized' when the lab has been finalized. The due date will either be posted here or announced in the class.

This quarter, the labs will be demoed to the grader, not electronically submitted.

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 35% of the final grade.

Contents:

Lab 1
Lab 2
Lab 3

Lab1
Curve Modeling
10%; Be ready to demo April 20
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.) Your initial
set of points may be input as a set of ordered points in plane.

Bezier curve - one curve for all the points
Cubic B-spline with uniform knot vector.
Subdivision curves using repeated de Casteljau method.

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).

cubic Bezier enforcing C¹ continuity at juntions (by repositioning control points)
rational Bezier
arbitrary order B-spline with arbitrary knot vector
NURBS.

(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 is simultaneously updated; optimize so that the entire curve does not have to be redrawn and local control is in effect.

Lab 2
Basic Data Generation
10%; Due May 16 for demoing

Finalized

Write a program that can generate basic geometric models. Your program should provide reasonable user interaction. Using
Lab1 generate surfaces implementing the following techniques:

surfaces 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. 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 (curve) 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:

   #-of-vertices=n #-of-faces=m
   x₁y₁z₁
   x₂y₂z₂
   ...
   x_ny_nz_n
   #-of-vertices-in-first-face=k₁v₁₁v₁₂... v_1k1
   #-of-vertices-in-second-face=k₂v₂₁v₂₂... v_2k2
   ....
   #-of-vertices-in-mth-face=k_mv_m1v_m2... v_mkm
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

You are encouraged to use this C++ mesh code mesh.cpp mesh.h  for constructing your solids.

·               This code will maintain all of the connectivity/adjacency information that is required when doing subdivision surfaces in Lab 3.

·               This code will NOT compute any solids or subdivision, Bezier, or b-spline surfaces - you will still need to compute the actual solids and surfaces with your own code.

·               The basic way to construct a mesh (e.g. when building a solid in Lab 2):

        Mesh m

        For each facet in solid

           Add facet to m

        end for

·               After constructing the mesh, you will be able to access the vertex-facet, vertex-edge, etc connectivity that is needed for subdivision surfaces

·               For more information, visit here

Extra Credit:

Lofting - loft a surface between multiple contours (5%)

Lab 3

(Finalized)

Surface Modeling

15%; Due June 4 for demoing

Generate control polyhedron using Lab 2. You should generate surfaces with boundary and without boundary.
Do the following surface types:

1. (7%)

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.

2. (8%) (subdivision surfaces. Use some examples where the initial control polyhedron is not a regular rectangular mesh)

Doo-Sabin surface
Catmull-Clark surface
Loop surface

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

To receive top grade you will have to enhance the functionality and user interface in a significant manner other than the
basic ones. For example, you can choose to do:

Reparameterize by arclength (you can use a brute force approach) prior to polygonization.(for 1) (Extra credit 5%)
Use smaller spacings of u and v till a planarity criterion is satisfied (for 1) (must do)
Use some arbitrary mesh to apply subdivision and demonstrate the convergence of the extraordinary points. (for 2, must do) Use Hole example.

You are encouraged to use mesh.cpp and mesh.h for constructing your solids.

·                     This code will maintain all of the connectivity/adjacency information that is required when doing subdivision surfaces in Lab 3.

·                     This code will NOT compute any solids or subdivision, Bezier, or b-spline surfaces - you will still need to compute the actual solids and surfaces with your own code.

·                     The basic way to construct a mesh (e.g. when building a solid in Lab 2 or during a subdivision iteration in Lab 3):

         Mesh m

         for each facet in solid

            Add facet to m

         end for

·                     After constructing the mesh, you will be able to access the vertex-facet, vertex-edge, etc connectivity that is needed for subdivision surfaces

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, (extra credit 10%)

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

syllabus

Last updated 05/22/08

CSE784 Labs

Lab1 Curve Modeling 10%; Be ready to demo April 20 Finalized

Lab 2 Basic Data Generation 10%; Due May 16 for demoing