Ray Tracer Checkpoint 7: Tone Reproduction and Final Code Submission

Assigned: February 2, 2011

Due: February 9, 2011

See assignments overview page for general information.

Introduction

The ray tracer programming assignment is divided into seven checkpoints:

1. Setting the scene
2. Camera modeling
3. Basic shading
4. Procedural shading
5. Recursive ray tracing - reflection
6. Recursive ray tracing - transmission
7. Tone reproduction

This is checkpoint #7, "Tone Reproduction".

Objective

Using your program from Checkpoint #6 (without extras), the task for this assignment is to take your generated image from CG units to real units. You will change your ray tracer so that it:

• Maps lighting units (0-1) to real lighting units
• Applies a tone reproduction operator to compress these simulated radiances to display radiances

The L_max argument will be used as the maximum luminance in the scene (i.e., all lighting units will be multiplied by it, so that the maximum CG lighting value of 1 will be set to this maximum physical value).

The L_dmax argument is the maximum luminance of the display device. For our purposes, we will use a value of 100 units for this.

You will implement two different TR operators:

• Ward's operator from Graphics Gems IV (perceptual)
• Reinhard's operator (photographic)

Equations and algorithms for these are given in the Checkpoint 7 lecture notes. In particular, note the "quick and dirty" approximation of pixel luminance values from RGB values, and suggested values to be used in the Reinhard calculation.

What to Submit

To submit your solution, do the following before midnight on February 9, 2011:

• Place six images on your web site showing the results
  • Two TR operators, three different L_max values for each (as specified in the Checkpoint 7 lecture notes)
     
• Send me email to let me know you have posted your results
   
• Submit a zip of all your raytracer code electronically to the appropriate myCourses dropbox. Note you must include a Readme file which documents the platform that you worked on as well as instructions for getting your code to compile.  

As it is extremely important to continue to make progress as the course progresses, late deliverables will be penalized 10% for each day late. There is an exception to this rule: if you anticipate any problems with meeting deliverable deadlines, see me well in advance (ideally, at least one week) of the deadline that might be missed, and we can attempt to work out alternate arrangements.  

Extras

Recall that you must do at least four "extras" in order to achieve the full 100 points for the programming assignments. "Extras" are worth five points each; this assignment has one possible "extra":

• Modify the Reinhard operator so that you can specify what luminance is to be used as the "key value":
  • Constant value
  • Value at a pixel

If you choose to do this extra, put at least two additional images on your web site illustrating at least two different "key value" selections (and describe the selections).