Computer Graphics (CS4300) 2012F: Assignment 6

DUE: 9pm, November 28, 2012

Worth: 10% of your final grade

Goals

• understand ray tracing
• implement Lambertian diffuse and Phong specular shading
• render shadows

Assignment

In this assignment, you will generate a realistic image of a 3-dimensional scene composed of spheres floating between you and the view plane. You will use ray-tracing and a local illumination model to generate your image.

General description

• Your program should be able to handle at least 5 spheres. Each sphere is given by its center (cx, cy, cz), its radius, and its color (R, G, B), diffuse and specular coefficients, kd and ks, and specular exponent e.
• The positions of the viewer and the single point source of light are each given by coordinates, e.g. (vx, vy, vz) and (Lx, Ly, Lz).
• The information for your scene must be read in from an input file.
• Use the methods presented in class to determine the RGB color of each pixel in your image. You may draw these directly to a window on the screen or to a ppm file or both.

Develop your program in these stages.

1. Generate a flat image using only ambient light. This way you will know that your program is finding the spheres before you go on to work on shading and shadows.
2. Add shading to your image using Lambert's Law for diffuse lighting.
3. Add shadows cast on the view plane by following a ray from each visible back-plane pixel to the light source.
4. Add shadows cast on the spheres by following a ray from a visible point on a sphere to the light source.
5. Add Phong highlights on the spheres.
6. Make the viewplane visible (i,e, not black) and add shadows cast on the view plane by following a ray from each visible back-plane pixel to the light source.
7. Extra credit possibilities:
   • multiple lights
   • colored lights
   • reflective objects (recursive ray-tracing)
   • Gouraud shading (Compute the color at each vertex and use barycentric coordinates to blend the values.)

See Building a Ray Tracer - Page One for sample images. Note that the small images on that page are links to larger images.

Grading

These grading guidelines will be used for all programming assignments:
Your project will be graded on:

• correctness (60%).
• style of your program (10% )
• documentation:
• • inline comments (10%)
  • README (10%)
• quality of the resulting image(s). (10%)

Turn In

• all sourcecode for your project
• data files for up to 3 scenes
• a README.txt file as instructed in the submitting instructions.

Follow these instructions for packing up your project and submitting it.

Grading

Your project will be graded on:

• correctness (60%)
• style of your program (10% )
• documentation and inline comments (10%)
• README (10%)
• quality of the resulting image(s). (10%)

Some points may be subtracted (up to 10%) if you need substantial help from the professor to make your program run.