The reason therefor is the short length of the track. The first wagon is almost down the hill, when the last one is just at the top of the hill. Remember this is a (really quickly drawn) test track.
For these 713 frames my (too) old computer computed a whole day 
I think, that I’m gonna render the final animation on some machines at university doing a 3D motion blur or do a fast 2D-blur.
Well, here is my final animaton. Since I don’t have access to the Sorenson pro codec, I had to compress my movies with the standard edition (which has no way to control the encoding). Therefore I provide some alternative AVI-files using xvid/divx codecs. The quicktimes are 320x240 and the AVIs are 640x480 (bigger image size and smaller file size :argh: ).
Edit: CoryC has recompressed my DivX videos using the Sorenson Pro Codec.Thank you very much! The links now point to the new versions.
Complete ride of the rollercoaster with an on-wagon cam:
Quicktime (8.8 MB)
avi (19.6 MB)
A short piece of the track from a 3rd person view
Quicktime (2.1 MB)
avi (6.8 MB)
A wireframe view (simplified geometry as seen in the viewport of Houdini)
Quicktime (4.4 MB)
avi (2.9 MB)
And the last video shows the procedural pillar generation. The distance between the pillars is decreased over time. The track crosses itself and the pylon, that would cross the lower piece of the track will be removed, if it would intersect it. In the background you see some other pillars removed, too. This is due to the fact, that two pillars would stand too close together in the hard turn of the track. Then one of them will be removed.
Quicktime (0.5 MB)
avi (0.5 MB)
Summary:
Completly procedural roller coaster system (animation and build up).
Interactive simulation (including scrubbing of the timeline and adjusting simulation parameters like gravity in realtime). This is a great advantage: You can view the end of the animation and tune the drag coefficient, so that the coaster is just about the reach the end of the track and not stick somewhere in a minimum.
Not a single keyframe set (except in the 3rd person movie for the camera)
Animation length 1685 frames.
Animation length 1min 7 sec.
Here are the four steps how to build a coaster (shown using the short piece of track of my first test animation):
1st step: Draw a NURBS curve:
2nd step:
Apply an operator, that starts the orientation editing. Here the coaster is always oriented upwards (even in the top of the looping).
3rd step:
Orient the small u-shaped objects to resemble the orientation of the coaster you want (create loopings, twists, …)
4th step:
Apply again an operator, that recreates the curve you have drawn. This time the curve has a point attribute coaster_orientation. This tells the build system how to orient the tracks.
The rest is all procedural. The coaster is made of some basic building blocks:
which will be place at the appropriate positions and orientations.
Wow! Wow! Wow!
This is great! I love it! Wonderful piece of work. Absolut no crits. I’m astonished.
I’ll check now others to see if someone is better, but i’ve never expected anything close to that.
Thumbs are up and i’m beat.
You Houdini Master you. 
This is great stuff - it looks really impressive. And to think that now the hard work is done, it wouldn’t take much to lay out a new track and have everything fall into place.
The only thing I can spot is something wacky going on at around 35secs in the Full.avi (some sort of brief intersection or something).
Very well done, I like the design of the track. But to me it still feels a little slow, maybe it just because your track is spread out more and you dont have anything flying past the coaster.
The wire frame video feels faster, but there the same, I dont know…
Anyways, great job. I like it alot
Vulcan has a point.
This was beautifully done, but it really doesn’t seem quick (final render). I think because it lacks landscape. You won’t believe what props can do outside the coaster to give it a sense of extreme. It needs something to whip pass. Beautiful coaster layout, but not adventerous due to the fact I can not sense the speed and vertigo.
Thanks for the nice crits. Concerning the “slowness”, I think, that it has to do with the missing props, too. You don’t really have a sense of size in the video. But unfortunately I only had one evening to build the final coaster, since I posted my last test video (including the fixing of some numeric instability problems, see below). So all the plans I had, had to be skipped Perhaps I’m gonna do another version of it next year (with better environment and people sitting on the train).
Another problem with the video is, that I couldn’t render with motion blur (would have taken too long).
@dante: Yes, the shaking I’m glad you like it. It was unintented. It results from instable numeric calculations due to the length of the track. That was really a problem: Till this final coaster I always used the path animation functions Houdini provided. I think houdini has some hard coded derivation scheme build in to compute the orientation of the object on the path. This was much too unstable to compute the orientation of the train on the track. On hard turns, the cars were rotated up to 90 degrees off of the track. So I had to do my own stuff. I’m glad Houdini is so flexible to support such things.
Deadlines and personal time has it toll, I understand, Frank. It was a pleasure to see what you have finished, though. An inspiration for many newbies on learning the craft. People such as myself wouldn’t know the first thing to do to achieve what you have, only give a personal perspective.
Keep it up, and I would love to see this finished soon. I’m sure it’ll be a blast!
Really well done Franck!
I am wondering how did your lighting? Is it HDR? How do you manage to create that lighting?!
Your Sim is really nice!
Houdini is so interesting!
Thanks you like it
The lighting is nothing special. Just a simple three light setup using a yellowish key light and a bluish fill light. It’s funny how much you get used to all those hdri images all-around. Everytime you see an image of gray objects under a colored sky, you think, that this must be an hdri rendering… :rolleyes:
Frank have you posted this on sidefx’s website or on odforce.net? if not you should. Very nice job.
Cheers,
Nate Nesler
Excellent work. This peice is simply blowing my mind. You’ve actually captured the feeling of “nausea” I get when riding coasters. I actually get a little seasick watching!
Great!
-pod:thumbsup:
Great work! :bowdown: And thanks for the AVI! Because MOV is the natural enemy of (my) Windows. 
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