EMAIL: angella@tsi.u-bordeaux.fr NAME: Franck Angella & Arnaud Vallat TOPIC: UNBELIEVABLE COPYRIGHT: I SUBMIT TO THE STANDARD RAYTRACING COMPETITION COPYRIGHT. TITLE: Mir Is Crashing COUNTRY: France WEBPAGE: http://www.tsi.u-bordeaux.fr/angella/raytracing.html RENDERER USED: Povray.3.02.watcom.win32, Povray.3.1e for Linux, Microsoft Visual C++ 5.0 TOOLS USED: 2 brains, 4 hands RENDER TIME: 82 hours HARDWARE USED: 2 PII350 (64M & 128M) IMAGE DESCRIPTION: -- Place de l'Etoile, Paris, on Wed, 11 August 1999. As predicted by a famous haute couture designer and by the 16th century French seer Nostradamus before him, the burning Mir space station crashes down in the center of the city, directly in the 'Arc de Triomphe'. This exactly happens during the total solar eclipse occuring in France. Note: Scientists proved that the Mir station won't crash down in Paris. So, please, do not cancel your holidays :) DESCRIPTION OF HOW THIS IMAGE WAS CREATED: Here is a brief description of our common work, followed by our two different contributions descriptions. COMMON PARTS * The whole scene was rendered using a focal blur, in order to highlight the most important part of it. There is a second reason for using the camera focal blur feature: the scene uses a lot of little particles around the Mir station, which used to disappear when using the antialiasing mode (except of course if we have had more time to run more accurate antialiased renderings). The final result with a focal blur let these particles visible; ok, we admit that there is a part of black magic in it, but we are working on understanding why it works ! * There are two ground fogs and an isotropic scattering atmosphere, mainly used so that the beams of streetlights can be visible. * The scene uses a main area light source with atmosphere off. Another area light source is placed under the big halo so that the scene looks orange around the Mir station. All the other light sources use atmospheric interactions. There are 4 of them around the "Arc de Triomphe" and one for each streetlight. * In addition, radiosity was used for the final rendering, in order to intensify the lighting effects. * The scene uses a lot of objects (about 280,000). It is memory-greedy (365M is the peak memory used...). We choosed to skip the light buffer precalculations (-UL switch), thinking that our computers were dying during the parsing stage... The zip file downloadable on the IRTC website was limited to the first row of buildings. The background buildings were greatly simplified to reduce the size of the zip file. We can provide the whole script if you want it. * We wanted to add some logos on this picture so that it would look like a TV snapshot. For those who read (and maybe write in) the IRTC discussion mailing list, thank you for your advices. Unfortunately, we hadn't time to re-render the final picture. The major issue to solve was to add a logo (with a transparent plane in front of the camera for example) while using a focal blur camera (of course with the logo not being in the focal plane). And we found a way to do it ! An easy solution is to use a transparent and totally reflecting plane in front of the camera, but rotated from 45 degrees. Then, place the logo or any object you want to appear in front of the camera above the plane. The distance must be chosen so that the optical paths from the camera to the focal point and from the camera to the logo are the same. Even with a focal blur, the logo looks sharp. THE CITY (Franck) * All the buildings were created using CSG. The scripts (18M !) were generated using different C programs. Here is a short description of how it was done: 1. A first program was written in order to get the corners of each building using the mouse. The buildings that you can see on the picture are located at the REAL places. This was done using an aerial photo of the "Place de l'Etoile" in Paris and clicking the buildings' corners. 2. The second program is used to link all the corners (vertices). 3. We then have groups of buildings (neighboring buildings). The third program determines whether a building side is a façade or not. It then generates the whole script. There are a lot of parameters such as the number of floors, the angle of the roof or the size of a window. Most of those parameters are slightly modified using random variations for each façade. The scripts contains the position of random chimneys and antennas too. In addition, some windows are lighted and some other are not (in fact there are no lights, but different textures only). To conclude this part, let's say that the buildings are at the right places, but of course they do not look like the real ones. The C program generates complete buildings given their corners only, so the global view makes it look like Paris Haussman's buildings. 4. Three other programs were created to manually place sidewalks, streetlights and trees. We would like to thank Paul T. Dawson for his ptd_tree include file, which was used in this scene for the trees. * The "Arc de Triomphe" only uses CSG too. The sculptures are basic height fields using pictures of the real monument. Four spots light up the construction. MIR STATION & PAVING STONES (Arnaud) * In order to destroy the Mir station, we first had to build it ! This was done using CSG and a lot of patience. The measurement of the station were taken in a scientific journal. Even if only a small 'complete' part of the station can be seen on this picture, the whole thing was modelled. Each part of the station is a distinct object, so that it was easy to destroy it, by moving and rotating each part (solar panels, satellite dishes, etc.) from its initial position. * The flame was done using an emitting halo. The container is a scaled sphere. In fact there are six halos. One of them is the flame, the other is a red light source with the looks like keyword (the looks like object is a dust halo). With such a light source, all the parts of the Mir station cast shadows on the ground and on the buildings. The other halos use conic or cylindrical containers to produce the steam ribbons. These halos used to work well without the use of atmosphere. With the atmosphere, white halos saturate the picture (white spots). That is the reason why the main halo (the orange one) container was removed (using the CSG difference) from the white halos. * The particle/scrap is a collection of randomly rotated and translated objects. Those objects are little pyramids (mesh objects) which reflects lights. * The paving stones are a collection of superellipsoids. The script was generated with a C program. This program calculates the position of each object, so that there is no gap between them (surface cobbling). In addition, each object is randomly rotated in order to have a 'chaotic' surface.