Lab2

Assigned: October 15, 2007

Due: October 29, 2007 11:59 PM

Lab overview: Enhance your ray tracer from Lab1 to include Phong illumination, shadows, reflections, and refractions

Objective: Upon finishing this lab, you will learn how to write a recursive ray tracer that includes global illumination effects such as shadows, reflections, and reflections.

Tasks:

1. Remove the simple illumination model used in lab1 and replace it with the Phong illumination model.

1.1. Assume the color of the light is white, i.e., (1,1,1)

1.2. Ambient: Use 0.2 as the ambient reflection coefficient (Ka). Multiple this to the ambient color of the object

1.3. Diffuse: Scale the object’s diffuse color by N.L, where N is the object normal and L is the light vector

1.4. Specular: Set the shininess to 1000 as the specular exponent of the cosine between V and R, where V is the

vector from the point to the camera, and R is the refection ray vector. Use the specular color of the

object as the specular reflection coefficient (Ks)

2. Add shadows to your ray tracer. For each visible point, loop through the light sources. If the point is facing to the light source (dot product of normal and vector to the light is positive), cast a shadow ray and test for shadow.

3. Add reflection: include reflection rays in your ray tracer.

4. Add refraction: include refraction rays in your ray tracer. Use an index of refraction of 1.0 for air and 1.5 for all other object material. Blend the color of the surface of the object with refracted light.

5. For reflection and refraction, set your recursion level to 3.

6. Change your ray tracer command line to

rt <input.iv> <output.ppm> <xres> <yres> <shadow_on> <reflection_on> <refraction_on>

where <shawdow_on>, <reflection_on>, and <refraction_on> are 1 or 0 to turn the individual effect on or off.

Lab submission

Submit your source code (.C and .h) and Makefile. Do not submit any executable files. Our grader will use the sample .iv files in the Data director of the sample_read_iv folder to test your program. If you have some nicer scene files that you want the grader to use, you can submit them too.

Submit a readme file specifying what are being submitted and how to compile and link your program.

Use the following command on stdsun to submit your lab2

> submit c681aa lab2 <names of all your files>

Notes about the submit program

The 'submit' program submits all of the files at once, not one at a time, previous submissions for a given lab are completely removed. Or put another way; each time the submit command is issued for a given lab, ALL of the previously submitted files are clobbered.

That means that

> submit c681aa lab2 lab2.c
> submit c681aa lab2 readme

will result in ONLY 'readme' remaining in the lab2 submission

You should do the following:

          > submit c681aa lab2 lab2.c lab2.h .... readme
          or
          > submit c681aa lab2 lab2_dir

Where 'lab1_dir' is a directory containing all of the lab1 files to be submitted, or best of all (for both student and grader) is:

> cd lab2_dir
> submit c681aa lab2 .

Submit will immediately print submission information to the submitter. Use 'man submit' if you have any other questions.

Late Penalty

You should submit your lab on time. We are on a quarter schedule, which is pretty tight. Being late for one lab could affect the time left for you to complete subsequent labs. All labs are due at 11:59pm of the specified due data, and there is a 10% penalty each day for up to 50%. After that, you get zero.

Grading Criteria

Grading of the labs will be based on the following:

• 90%: Correctness and adherence to assignment specification.

• 10%: Readability, structure of code, use of comments, adherence to lab procedures (submitting, naming conventions, etc.)

The grader will grade the labs. If you have problems with the grade you received on your lab, see the grader first. If you can't resolve the dispute with the grader, then see me. However, in order to maintain consistent grading for everyone in the class, I am not very inclined to alter grades that are assigned by the grader.

Don't copy labs. Discussion of lab assignments is allowed and encouraged. However, you need to complete the lab all by yourself. Labs which are too similar will be handed over to the Committee on Academic Misconduct and handled by them.

Last updated: 10/14/2007 Han-Wei Shen