Clarification and Changes:

Synopsis: Your program will load a polygonal object and use OpenGL to render it. A command line argument to your program will specify the name of the model to load, the definitions of two planes, and rendering constants. You will write code to clip the model to the two arbitrary clipping planes using the Sutherland-Hodgman algorithm. Your OpenGL program will also support mouse navigation through the model. Grad students, note that your program must also support interactive repositioning of the clipping planes.

Specifics: We are providing a Makefile and a C++ skeleton file named assign2.C. The assign2.C file will set up lighting so that front-facing polygons will be drawn one color and back-facing polygons another. You will modify the functions in assign2.C, adding code to draw the scene and handle callbacks. Some special things to notice about the code:

• Your program must accept one command line argument that will be a character string of no more than 256 characters. The program must execute from the command line like this:

  prompt> assign2 parameter.file

• The four lines in your parameter file must look like this:

  modelname.poly
  A B C D
  E F G H
  X
  

  • Where the .poly file is defined according to these rules. We will be using these .poly files to test your code. Note that the horse has inconsistent polygon orientation and may look strange even before clipping -- debug on simpler models.

  • A B C D are the four doubles that define the parameters of the first implicit plane equation: Ax + By + Cz + D = 0. Clip away all geometry found in the negative half space formed by this plane

  • E F G H are the four doubles that define the parameters of the second implicit plane equation: Ex + Fy + Gz + H = 0. Clip away all geometry found in the negative half space formed by this plane

  • X is the integer that specifies rendering globals. A value of '1' indicates that the clipping planes should be drawn. A value of '0' will turn off the rendering of the clipping planes.

• The user must be able to navigate through the world using the mouse.
  • Left button + drag = rotating the camera around the polygonal model. The camera should remain a constant distance from the model, but the translation of the mouse should correspond to longitudinal and latitudinal rotations of the camera about the model. Picture the way you use a trackball.
  • Right button + drag = zooming in and out of the model. Forward and rightward movements of the mouse move the camera closer to the model's center. Downward and leftward movements move the camera away from the model.

• Use the Sutherland-Hodgeman algorithm to clip all polygons that penetrate, or fall within, the negative half spaces of either (or both) of the clipping planes.

• (Grad students only) Use the center mouse button to interactively select one of the clipping planes. Once selected, use the left and right mouse buttons to allow the user the freedom to reposition the selected clipping plane. Translation is all that I require, but rotation would be nice.

Advice: OpenGL has direct support for clipping to arbitrary planes. Don't even think about it. :-)

Turning in the assignment:

• Verify that your code compiles and runs correctly on sgi-1.unixlab.virginia.edu. We will use this machine for compiling all assignments.
• Write a README file with your login, your name, what you did, and anything you'd like us to notice or know about your demo.
• Verify that the line in your Makefile beginning "SUBMIT =" includes all relevant files. This includes all source code (including header files!), your README, and the Makefile itself. You should not include object (.o) files, libraries, or the final executable.
• Type "make submit" in the directory containing your code.