CSE681 Lab 1

• We are not going to use OpenInventor this quarter. This is a change from recent previous 681 classes. This will change the labs and class notes.
• Professor Shen has some Lab Help pages that you might find useful. However, note that my lab assignments may or may not be the same as Dr. Shen's - so when he refers to something about a specific lab assignment, you need to relate that to my assignment. (But you'll have to ignore the OpenInventor stuff there).

Objective

• In this lab, you will create the basic structure for your ray tracer including the basic ray construction code and ray-sphere intersection code. However, these can be simplified by using assumptions about the location of the camera and the sphere.

Assignment & Requirements

• Call your program lab1.
• Use whatever classes and program organization you want - but the program should be documented and easily 'readable' by the grader.
• You can refer to the book, the web, other books, etc. to see code fragments for the various tasks you'll have to program - but write your own code. Questions concerning code will be on the midterm and final.
• Build a ray tracer that uses a pre-defined camera, intersects a single sphere of radius 1 centered at the origin, shades it according to the normal vector at the intersected point.
• To shade the sphere at a point of intersection:
  • At the visible point of intersection, calculate the normal vector (vector from the center of the sphere to the intersection point),
  • normalize the normal vector
  • Use the z component of the (normalized) normal vector to scale the color of the sphere, clamping it to the ambient value at the low end.
• Default scene consists:
  • background color of (0.0 0.6 0.6)
  • no lights
  • ambient value of 0.2
  • one sphere
    • at (0,0,0)
    • radius of 1
    • color of (0.8 0.2 0.2)
  • camera
    • position at (0.0 0.0 1.5)
    • center-of-interest, or lookat point, of (0.0 0.0 0.0)
    • half angle of view of 45 degrees
    • aspect ratio of 1.0
    • hither and yon distances of 0.1 and 100.0
    • tilt angle of 0.0 degrees
    • resolution of 400 x 400
• When a ray intersects the sphere, compute the intensity of a point on a sphere thusly:
  • compute the normalized normal vector of the point on the sphere
  • set the intensity to the maximum of the ambient value and the z-component of the normal vector
• Write the image of the ray-traced scene out to a portable pixmap file, called output.ppm. In the PPM file, use 255 as the maximum color component.
• Of course, you can develop your program on any platform you like. But make sure, before you submit it, that the grader can compile, execute, and view the output under UNIX using the commands shown below.
• Submit the source code for your program. For example:

  submit c681aa lab1 lab1.c makefile
  

  Of course, you can break it up into multiple source files and submit those. For example:

  submit c681aa lab1 main.cpp camera.cpp sphere.cpp light.cpp makefile
  

  - just as long as the grader, under UNIX, can make and execute your program, and then find the output in output.ppm:

  make
  lab1
  convert output.ppm output.jpg
  display output.jpg
  

NOTES

For example, at 45 degrees field of view with the observer at z=1.5, the virtual frame buffer should be at z=0.5 and the top of it should be at y=1.0.

Similarly, with a sphere centered at the origin with radius 1, all intersection points should be a distance of 1 away from the origin. The z-coordinate of all normal vectors of all visible points should be positive.