TITLE: The Bell Tower
NAME: Roy Schulz
COUNTRY: Germany
EMAIL: royschulz@gmx.de
WEBPAGE: http://www.crosswinds.net/~royschulz/
TOPIC: Inner Workings
COPYRIGHT: I SUBMIT TO THE STANDARD RAYTRACING COMPETITION COPYRIGHT.
MPGFILE: belltowr.mpg
ZIPFILE: belltowr.zip
RENDERER USED: 

  rendrib from BMRT 2.5.0.2 ... 2.5.0.8 for Linux glibc2

TOOLS USED: 

  Moonlight Atelier, The GIMP, BMRT's composite and rgl,
  tifftopnm, ppmtoyuvsplit, mpeg

CREATION TIME: 

  I can't say exactly, but it took lots of my spare time.
  Longest rendering times:
  3 days for the second shot (cam move from clockwork to bell)
  2 hours for a single frame of the fourth shot (falling trigger)

HARDWARE USED: 

  AMD K6-2 400 Mhz, 64 MB RAM

ANIMATION DESCRIPTION: 

  The animaton shows a bell tower and its "inner workings". It starts just
  before four o'clock, introduces the tower and its inside. Then it shows
  the minute hand going to twelve, the striking mechanism working and
  the bell being struck. Finally you see the tower from the outside again
  with some birds being startled by the bell's sound.


VIEWING RECOMMENDATIONS: 

  For Linux mpeg_play and MpegTV work fine. With the latter you get the best
  quality. It's the only player that shows the waving leafs without flickering.
  Windows Media Player has the advantage of hardware accelerated fullscreen.


DESCRIPTION OF HOW THIS ANIMATION WAS CREATED: 

  
  The whole thing was coded in C except the bell, which I modeled in
  Moonlight Atelier.
  
  For each shot I wrote its own C program using the C binding of RenderMan
  that comes with BMRT (ri.h and libribout.a).
  
  I started with the trees of the first shot. They were made by a simple
  recursive algorithm (tree.inc in zip-file). Both trees are exactly the
  same, just viewed from different angles. The waving of the twigs was made  
  using sine and cosine, so the movement is exactly circular. This is  
  okay, because the shot is on screen only for four seconds. So you won't  
  notice the regularity, unless you look for it. The tower was made with CSG.
  The birds are extremely simple. They consist of three elipsoids only. One
  for the body, two for the wings. They are motion blurred for smooth
  movement without strobing. I wrote shaders for the roofs shingles, the
  clouds and the clock face. You'll find these in the zip-file. The trees and
  birds use the standard "matte" shader and the bricks are done with the
  "brick" shader that comes with BMRT.
  
  The most work I did for the second shot. There is so much detail in it. I
  started with the architecture: the room, the roof, the dormers. CSG was
  used extensivly. Then I added the gallery and the stairs. I tried several
  lightings but none was satisfying. So I gave BMRT's radiosity a trial.
  After some playing with the parameters, the result was very good. To save
  rendering time, the radiosity calculation takes into account only
  architecture and gallery. Then I created the bell as NURBS in Moonlight
  Atelier. The gears are CSG again. Placing them correctly was the most time
  consuming job. The OpenGL viewer rgl from BMRT helped a lot, because it
  renders high resolution previews in no time. I wrote only a shader for the
  ropes. The clock face kept the shader from the first shot. Everything else
  was done with shaders that are provided with BMRT. The camera movement uses
  sine and cosine in several ways. For the smooth shadows I utilized the area
  light feature of BMRT. Unfortunately I couldn't afford longer rendering
  times due to the close deadline, so there is still a little noise.
  
  The third shot is simple. I copied the relevant parts from the first shot
  and let the hand move almost unnoticable.
  
  In the fourth shot you see the trigger falling exactly at four o'clock.
  This is visible only for a short moment. So I used depth of field to focus
  the viewers attention onto the trigger immediatly. Beyond that there is
  nothing special. I just copied the relevant parts from the second shot.
  
  Again I copied relevant stuff for the fifth shot, changed the camera,
  introduced the movement of the striking mechanism and motion blurred the
  escapement.
  
  For the sixth shot I used depth of field again for the same reason as in
  the fourth shot. The bell was improved over the second shot by applying
  the "supertexmap" shader from the "Advanced RenderMan" book with an
  appropriate bump map (included in zip) which I created with The GIMP.
  
  And once again I copied for the final shot. This time the first shot had to
  serve. I took away the two birds and added lots of them instead. I made
  them fly into arbitrary directions to make them look as if they were
  startled by the bell's sound.
  
  The animation was rendered with PixelSamples 2 2, except the depth of field
  shots, which have a PixelSamples 3 3 statement.

  I created title and end credits with The GIMP and utilized BMRT's composite
  for the fading.
  
  The C-sources are not included in the zip-file, because they are so large and
  not very readable. So I decided to provide only interesting parts like the
  tree function.
  
  If you have any questions beyond this description, feel free to ask me.
  There are no secrets.