The LDraw Administration Team proudly presents Rachal – The RAytraching CHALlenge to spur people's creativity and show different interpretations of the same source material. Please note that this is not a contest! All entries will be added immediately to a gallery [4] at LDraw.org to be shown but not voted. We also plan to run this challenge quarterly.

RACHAL - The RAytracing CHALlenge

RACHAL 1 - Atmosphobic is the debut of a new series of challenges to be run from LDraw.org. These challenges are intended to encourage creativity and learning through multiple rendered versions of a single model. By presenting a single model for rendering and encouraging discussion of the techniques used to render it we hope that all people with an interest in raytracing LEGO brand bricks can learn and improve. RACHAL is a follow-on to two previous challenges run by Tim Gould [5] at Lugnet [6] ([1] [7] and [2] [8]) and entries to either of these might provide techniques and ideas for this one (search Lugnet for "Remix Lenin" or "Remix Disco" to find entries).

In contrast to the second challenge, we opted for a fairytale-like winter scene leaving it completely up to the entrant to decide on interpretation in lighting and ambience. As you might have already figured out from the title "Atmosphobic" it encourages the use of special effects such as snow, fog or strong wind. In addition the presence of the cloak allows playing with textures and perhaps more complicated systems for rendering cloth. All entries will be displayed in the Atmosphobic gallery [9]

This challenge will run until Saturday the 31th of March. All entries to the competition must be in before 6pm GMT on that day.

The following files are provided for download. The first is the MPD for the scene while the others are an example entry made by Tim.

• RACHAL_Atmosphobic.MPD [11] - Atmosphobic MPD file
• RACHAL_Atmosphobic_tg.png [12] - Example entry image by Tim Gould - On the Shelf
• RACHAL_Atmosphobic_Files_tg.zip [13] - Example entry files by Tim Gould - On the Shelf

The majority of rules are standard and are included at the contest rules [14] page. However, as each challenge is different we include the following special rules and clarifications.

• All entries should contain the file RACHAL_Atmosphobic_<initials>.jpg containing a picture of your entry. <Initials> should be the submitters initials. If submitting multiple entries please append a number to the initials eg. RACHAL_Atmosphobic_tg1.jpg, RACHAL_Atmosphobic_tg2.jpg etc. PNG format is also acceptable.
• It is very much preferred if all entrants also submit a file RACHAL_Atmosphobic_Files_<initials>.zip containing files that can be used to recreate the scene (see the main rules [15] for details).