This might give you food for thought, it certainly made my head hurt...

http://cs.brown.edu/courses/cs195u/lectures/lecture7.pdf

(I made a very simple potential fields program in Processing recently - code available if of interest!)

Woe...
Way over my head...

I was thinking more on a more basic level such as:

• OK, I am gonna use a 3D Array or a 3D Arraylist.
• Each cube has 26 neighbours (relative pos being -1,-1,-1; -1,0,-1; -1,1,-1 etc. except for 0,0,0)
  
• Each cube has 6 entry points for tunnels (or 5)
  
• Each cube has 4 entry points for tracks upon it
• Each cube has 6 exit points for tunnels (or 5, unless there is a rocket in it to shoot the marble out of the top)
  
• Each cube has 4 exit points for tracks upon it
• exit point must not be the same as entry point (or it's a U-Turn cube, haha)
  
• When the marble exits at exit point C, this point knows which cube is the next cube for the marble and which of its entry points is used
• so we need one class Cube and one class EntryExitPoint
• each cube has a rule set, saying, when incoming at entryPoint B, next cube has relative position (0,-1,1) and next cube entry points would be C (or with special cubes when there is a magic gate in the cube, alternating maybe between two cubes or via random choosing between two paths)

So there is a marble manager function knowing, ok I am in that cube and coming from that entry point so now I am going to go to that cube and ...

I am just not too sure how to tell this in processing... 

But I have more ideas coming to my head thanks to you....

maybe we need a class Marble and a class RuleSet too... 

If you start with a class that describes a path as a list of points, you can describe how the marble shall move.

I look on some paintings of the beast I have here on paper (dunno where on the net)

it seems there are tunnels meant

• to lead to other tunnels (coming out in the middle of wall)
• and other tunnels meant to lead to a track which is on the next cube (which is therefore one position deeper than the current one).Those tunnels are coming out on the lower side of the wall of the first cube. Crazy.

Instead of thinking about this as cubes with exits, you could also see it more like a network of connected nodes. Define and connect cubes by their overlapping exit points (visualized by the blue dot in the example below). When you think of it in terms of connections, the whole thing becomes much more flexible and you are no longer limited by rigid blocks. In the virtual world you have much more freedom.

The Idea

1. void setup() {
2.   size(500, 500, P3D);
3.   fill(255, 0, 0, 50);
4. }
5.  
6. void draw() {
7.   background(255);
8.   translate(width/2, height/2, 350);
9.   rotateX(frameCount*0.01);
10.   rotateY(frameCount*0.01);
11.   box(6, 5, 5);
12.   stroke(0, 0, 255, 50);
13.   sphere(1);
14.   stroke(0);
15.   pushMatrix();
16.   translate(-13, 0, 0);
17.   box(20);
18.   sphere(1);
19.   popMatrix();
20.   pushMatrix();
21.   translate(13, 0, 0);
22.   box(20);
23.   sphere(1);
24.   popMatrix();
25. }

that's a neat idea...

I'd be inclined to get this working in 2D first, 3D would probably be a trivial 'upgrade' if there's no physics involved!

Questions!

Are the cubes all the same size and placed within a regular cubic (or cuboidal) space i.e. no 'overlapping'?
Can a marble pass through the same cube in different directions on the same 'run'?
If a marble enters at point A will it always exit at point B if there is more than one exit?
Can a marble enter at point B and exit at point A?

Questions answered

Are the cubes all the same size and placed within a regular cubic (or cuboidal) space i.e. no 'overlapping'?

No overlapping but I guess there can be cubes which are 5 times longer than a normal one.
see http://www.youtube.com/watch?v=VmX4-8y7Lyc

Can a marble pass through the same cube in different directions on the same 'run'?

sure. there can be several intertwined tracks in a marble machine (4 marbles start at different points into the marble machine) or one marble can pass through one cube several times, when there is a elevator e.g. carrying it up again and giving it another track to pass through the cube.

If a marble enters at point A will it always exit at point B if there is more than one exit?

No, as said, there could be a random generator in the cube or an alternating gate, putting it to two or more exits at random or with an alternating rule. But in most cases: yes.

Can a marble enter at point B and exit at point A?

Yes. The names of the points don't suggest a direction. When you rotate the cube by 180° it goes from A to B, otherweise from B to A. Both possible. I guess the cube must know the connection of AB or BA, but the direction doesn't matter in most cases.

Thank you so much for your thoughts!

Greetings, Chrisir  



The picture is actually very nice.

In processing our cubes can of course also float and don't need a cube under them.

Imagine: There could be cubes teleporting the marble or firing it like an catapult or
changing it's color or size, or elevators, anti-grav cubes, or size sorting crossings...




http://cuboro.ch/de/Info/Produkte/cuboro_Kugelbahn

http://cuboro.ch/cmsfiles/gesamtprospekt_cuboro_defi_2012_low.pdf

I posted a first attempt now onto OpenProcessing - please note it is the exact track as shown above.

It doesn't run in the browser, but if you want you can download it
and take a look.
I used processing 1.51 to make the applet but it runs in 2.0b7 when you remove the import
of opengl lib.

Thanks for all the help given above!

Watch the video now:
http://www.youtube.com/watch?v=gixziwrbJpg&feature=youtu.be


Code:
http://www.openprocessing.org/sketch/84284