LIMN-Ray Wiki

Introduction

LIMN-Ray is a raytracer written in C++, which started as a programming project for a subject at collage. The goal was to create a fast and slim ray tracing rendering engine, using approximations of the Phong lightning model.

LIMN-Ray implements the basic ray tracing algorithm without using recursion, in order to exploit parallelism. At the moment LIMN-Ray uses the OpenMP API to distribute the work between threads by interleaving rows of pixels.

Downloading the Source Code

You can get LIMN-Ray v1.0 source code archive at the download section or in the SVN repository @ Google Code.

SVN Checkout command:

$ svn checkout http://limn-ray.googlecode.com/svn/trunk/ limn-ray

Compiling instructions

The current instructions are for Linux systems, but you should be able to compile LIMN-Ray successfully if you satisfy the project's dependencies using your OS's alternatives.

To compile LIMN-Ray you need G++ >= v4.2 and the following libraries installed into your system:

• Xerces-c++
• GCC OpenMP (GOMP)
• PNGWriter

If you run an Ubuntu distro in your system, you can get the following Deb packages using apt/aptitude or the Synaptic Package Manager:

• build-essential
• libxerces28-dev
• libgomp1
• libpngwriter-dev

Once you have LIMN-Ray's source code and extracted it, just go into the './limn-ray' folder, I've included a makefile, so you should be able to compile using the Make tool by just typing 'make' and waiting until the compiling process ends.

Running LIMN-Ray

If you run LIMN-Ray without any arguments, it will start rendering the default benchmark scene, and output the result into the 'image_out.png' & 'image_out_zbuffer.png'.

You can add the '--help' argument when running LIMN-Ray to see the available options. This would display the following:

Usage: limn-ray [OPTIONS]
Options are:
  -o [FILENAME]	 Output file name without extension
  -v		 Toggle verbose
  -f [FILE]	 Render scene from XML scene file
  -t [n]	 Set number of processing threads

By typing the '-o' argument and appending a file name, FILENAME would be the prefix name of you output rendered image in PNG format. By typing the '-v' argument, LIMN-Ray would display a basic scene description of the scene it's about to render. This is useful when creating a scene and checking for errors in the XML description. By typing the '-f' argument and appending a file name, one can specify an XML file describing the scene. By typing the '-t' argument and appending an integer number, one can specify the number of running threads dedicated for the rendering process.

This is an example for rendering one of the sample scenes provided with the source code:

$ ./limn-ray -f sample01.xml -o sample01 -v -t 1

With this command, we have specified LIMN-Ray to:

• Render the scene described in 'sample01.xml'.
• To save the result render into the 'sample01.png' image file.
• Enabled verbose to show a brief description of the scene.
• Forced LIMN-Ray to use only one processing thread.