Computer Science 112
The Art & Science of Computer Graphics

Spring 2013, The College of Saint Rose

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This "bonus" assignment gives you the chance to gain experience using Bezier curves by constructing a stained glass window.

A Stained Glass Window

We saw in class that the message (bezier) sent to a Prism object will instruct it to treat its profile as a set of control points for one or more Bezier curves, rather than as a straight-sided polygon. We will use this construct to build panes of glass, some with curved sides, that fit together to form a stained glass window.

I would like to collect all of our windows into a larger model, so please follow the guidelines below very carefully to facilitate this.

• Create your window object as a Group of colored glass panes.
  • 3 to 5 panes is plenty, but feel free to be ambitious and include more.
  • Construct most panes from Prisms.
  • At least two panes must have a curved edge.
  • The window should be 5 units thick, though you may include one "unusual" pane that might be a different thickness or even not be flat. You might use a different primitive object type for this pane if you wish.
  • You may wish to have the edges of your panes meet exactly, or leave some (normally lead-filled) empty space between panes as a feature of your design. Still, the glass should cover almost all of the window area.
  • The window should be rectangular, and be between 60 and 100 units wide and between 60 and 100 units tall.
  • Plan the layout of your panes carefully. There will be graph paper available in the lab to aid in your planning.
  • Give your window a formal title of five words or less (in the spirit of titles of stained glass windows in churches). Use the description message to set this title.
• Create glass-like materials for your panes.
  • Pick a color of your choice. RGB colors have a fourth value that we have not used so far. It specifies how much of the light is filtered to take on the color of a transparent material as it passes through. The default value of 1 means no filtering, smaller values cause more of the light to take on the color of the material. I suggest a value around 0.6.
  • Make your glass highly transparent and perhaps slightly reflective and/or specular.
  • Set the refraction to 1.5, which is reasonable for glass.
• Your model should be submitted as a module (shared model) in a file named with your last name and "Window.scm", so mine would be called "TerescoWindow.scm". It should provide your window object, named with your last name (uncapitalized), followed by Window, so mine would be terescoWindow. Also provide your window's dimensions as defined constant values named with a similar convention: terescoWindowHeight and terescoWindowWidth. Your window should, by default, be placed in the xy-plane, with its lower left corner at the origin.
• Also create a simple model that shows off your window for testing and for creation of images for your wiki page. Include one "head on" image that shows the design of your window. Include at least one where you shine a spotlight through the window onto a white surface behind to see the colors of the window on that white surface. And finally, include one other setting not described here that you feel shows off your window.

Typical Model Layout

Your model will likely be organized as follows. First, define your materials.

(object redGlass Material
    (color red)
    (transparency 0.9)
    ...
)

Define panes of glass:

(define pane3Profile (<point-list>))
(object pane3 Prism
    (profile pane3Profile)
    (bezier) ; interpret profile as collection of bezier curves
    (scale 1 1 0.05) ; ensure 5 units thick (normally, it's 100)
    (material redGlass) ; assign a material
)

The panes will be added to a group that represents your entire window. At this point, also set a description for a title for your window.

(object terescoWindow Group
     (description "Finestra Noiosa di Jim")
     (add pane1)
     (add pane2)
     (add pane3)
)

Example Model

The example model shown in class is available to you for use as a starter, or at least as a guide as you develop your window. In the class shared folder, you will find a folder labs and the folder bezier within that contains my model.

Submission

1. Email a copy of the source code for your model (the scheme file, which should always be saved with a .scm extension) and your best image (which should always be saved in PNG format and using a .png extension) as attachments to terescoj AT strose.edu. Please include a meaningful subject line (something like "CSC 112 Studio/Lab Bonus 1 Submission"). Make sure your name is included in a comment in your model code, and that you have comments throughout the source code to make it easier to understand.
2. Rename your best image to include your name, then upload it to the wiki. For example, if you generate an image of a window with smiley faces and your name is Guy Smiley, you might call your image "GuySmileyHappyWindow.png".
3. Add a section to your wiki page named "Stained Glass Windows" that includes a link to your image and a description of your model that generated the image.

Grading

Your submitted model and image will be graded out of 20 points. Your grade will be based on how well the model meets the requirements, documentation, and presentation on your Wiki page. Documentation (comments) in your submitted Mead model should include your name, the assignment (Studio/Lab Bonus 1: Stained Glass Windows) and a brief description of the model at the top, and descriptions of sections of the model that might not be clear to someone trying to understand it. Your model code should always be nicely formatted. You can always select "Reindent All" from the "Scheme" menu in DrScheme to have the system format your code nicely. This will help with readability. Since it's so easy to do, there's no excuse for turning in poorly-formatted models.