| TITLE |
| |
| smallpt: Global Illumination in 99 lines of C++ |
| |
| CREDITS |
| |
| Author: Kevin Beason (kevin.beason [at] gmail.com) |
| Date: 10/11/2008 |
| |
| SUMMARY |
| |
| smallpt is a small Monte Carlo path tracer, and generates a single image of a |
| modified Cornell box rendered with full global illumination (GI). It does this |
| by solving the rendering equation, including ideal Lambertian, specular, and |
| dielectric reflection, area lights, anti-aliasing, importance sampling, and |
| multi-threading. It is only 99 lines of C++, but illustrates photo realistic |
| rendering in a correct, and concise manner. |
| |
| DESCRIPTION |
| |
| The source code for a small program that path traces a simple Cornell box and |
| produces accurate results in a terse implementation is given, which provides an |
| educational example to new graphics students (and seasoned alike), and yields a |
| ground truth image, all in an easy to read package. Never before has a correct, |
| complete, and functioning path tracer been presented so succinctly. Readers |
| will see ray-sphere intersection, Monte Carlo path tracing, Russian roulette, |
| importance sampling, anti-aliasing, and OpenMP multi-threading in a concrete |
| working example, which may be read from beginning to end in a single |
| sitting. The program compiles with GCC 4.2 down to a 16k executable and |
| produces a 1024x768 resolution image using 5000 paths in 2 hours on an Intel |
| Core 2 Quad machine. With slight modifications (smallpt4k.cpp) the code compiles to |
| under 4KB. |
| |
| FEATURES |
| |
| * Global illumination |
| * Unbiased Monte Carlo path tracing |
| * Cornell box scene description |
| * Ray-sphere intersection |
| * Soft shadows from diffuse luminaire |
| * Specular, Diffuse, and Glass BRDFs |
| * Cosine importance sampling of the hemisphere for diffuse reflection |
| * Russian roulette for path termination |
| * Russian roulette for selecting reflection or refraction for glass BRDF |
| * Antialiasing via super-sampling with importance-sampled tent distribution, |
| and 2x2 subpixels |
| * Automatic multi-threading using OpenMP |
| * Less than 100 lines of 72-column code |
| * With provided code changes, can compile to 4K binary |
| |
| BUILDING |
| |
| There are two versions of smallpt. The basic version is called "smallpt" |
| (smallpt.cpp), and is 99 lines. A second version, "smallpt4k" (smallpt4k.cpp), |
| is 102 lines but compiles to 4K instead of 16KB. It is just a |
| proof-of-concept. They compute slightly different images due to compiler optimization differences. |
| The 4 KB version takes 30% longer. |
| |
| 1) Modify top of Makefile to select the correct compiler. |
| 2) "make smallpt" (This builds both the regular version) |
| 3) "make smallpt4k" (This builds the 4K version. Requires sstrip, see Makefile.) |
| |
| USAGE |
| |
| The program takes one argument, the number of samples per pixel. This value |
| must be greater than 4 to accommodate the 2x2 subpixel grid. For example, |
| the included reference image was generated with: |
| |
| time ./smallpt 5000 |
| |
| This took 124 minutes (2 hours) on a Intel Core 2 Quad Q6600 2.4GHz machine |
| running Kubuntu Linux (32-bit Gutsy). |
| |
| The tiny version takes no arguments (5000 samples/pixel is hard coded): |
| |
| time ./smallpt4k |
| |
| Compilation requires gzip and ELFkicker's sstrip command. See the Makefile for |
| details. It executes in slightly longer time, and yields a slightly different |
| image due to compiler optimizations differences. |
| |
| The time command tells you how long the render takes and is optional. You can |
| view the image with most any image viewer. For example, if you have ImageMagick |
| installed: |
| |
| display image.ppm |
| |
| MORE INFO |
| |
| MINILIGHT - a minimal global illumination renderer, by Harrison Ainsworth |
| A similar, earlier project. More general but also larger (100x). The site has |
| some good information on Monte Carlo path tracing. Instead of repeating it |
| here, the reader is referred to that site: |
| http://www.hxa7241.org/minilight/minilight.html |
| |
| Realistic Ray Tracing by Peter Shirley |
| Almost 100% of smallpt is derived from this book. |
| http://www.amazon.com/Realistic-Ray-Tracing-Peter-Shirley/dp/1568811101 |
| |
| Henrik Wann Jensen's Cornell box images |
| The inpiration of the output generated by smallpt. |
| http://graphics.ucsd.edu/~henrik/images/cbox.html |
| |
| 100 lines C++ sphereflake raytracer, by Thierry Berger-Perrin |
| Ray sphere intersection code stolen from here. (No full GI.) |
| http://ompf.org/ray/sphereflake/ |
| |
| sf4k, also by Thierry Berger-Perrin |
| Idea for 4K-ness. (No full GI.) |
| http://ompf.org/stuff/sf4k/ |
| |
| C++ vs OCaml: Ray tracer comparison, by Jon D. Harrop |
| 105 line C++ ray tracer. (No full GI.) |
| http://www.ffconsultancy.com/languages/ray_tracer/comparison.html |
| |
| Introduction to Linux as 4 KB Platform |
| Some information regarding shrinking binaries to 4KB on Linux . |
| http://in4k.untergrund.net/index.php?title=Linux |
| |
