Hello,
I am trying to get a Dynamic Foam going and got help from a developer but we ran into some problems connecting centroids to establish a network in between the ‘foam bubbles’.
I have added extra information for why those centroids need to be connected and form a network, along with the problem (job) explained at the end.
I. Dynamic Medium
II. Fields and Boids
III. From Boids to a PBD Network
IV. From Curling Motion to Strings
V. Position Based Dynamics (PBD)
VI. The Problem (Job)
I. Dynamic Medium
The goal of my project is to create a kind on a Zero-player game, a bit like GoL, where cells fluctuate based on surrounding cells, and where the goal to generate Knots within a Dynamic Medium.
To get a sense of such a dynamic network think of a foam with bubbles where a fluid runs through the edges. These currents move from high to low pressure, forming circuits. The intensity of the fluid passing the bubbles can make the bubbles shrink or expand. Some currents will be able to line up and form closed circuits.
In 2D these structures are simple loops, in 3D these loops can form strings, and in a next step these strings form again closed-circuits -> knots.
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II. Fields and Boids
One way to get a model of bubbles and currents going was by using Boid-particles and Fields, which was tried in Processing. Here are short clips to show the interaction:
• http://imgur.com/a/Mp0SG
• https://vimeo.com/user37290268
A. In the first clip the Fields (red circles) keep their size while the small particles form a circuit.
B. In the second version the size of the Fields is influenced by the number of particles within: Expand <-> Shrink
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III. From Boids to a PBD Network
The problem with using Boids is that they have their limitations whereby the quick expansion of Fields causes the particles to be splattered around, interrupting the steady current and are splashed around.
Keeping the Boid-particles flowing is important, because a flow-circuit gives rise to organisational rules such as flows going against each other block each other, others can go along like an electronic circuit:
To fix these problems a move to PBD was made and hoping to create a network model that replaces the small particles.
flow -> edges
Fields changing size depending on the amount of flow through the edges:
• Having two Fields A.B. and in between from point a. to b. an edge.
• This edges (a.b.) can replace all the boids moving in between (A.B.)
• Edge (a.b.) can represents 1 or 1 million small particles or more, simplification.
• Between Field A. and B. a measurement of tension •-VVVVV-• (A/B)
• The more tension between (A.B.) the less flow there can be in (a.b.)
• Inverse the more flow there is in (a.b.) the less tension between (A.B.)
• The edge (a.b.) runs through the Fields A. and B, cooling or heating up Fields A. and B.
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IV. From Curling Motion to Strings
The basic idea is to get the bubbles moving through the medium thanks to self-regulating currents in between:
Like a sliding-puzzle where the parts can move to where there is space created:
Thus bubbles shrink on one side and expand on the other, so they can move around and get a rolling-curling-motion:
The dynamic curing motion could also turn around and close-loop into knots:
In 3D the wind up curls would be like these dansers waving strings:
http://www.youtube.com/watch?v=uvE5yt83WPU (at 1:44)
These strings can turn into knots etc. etc.
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V. Position Based Dynamics (PBD)
For a look at my current situation you can check this short clip, where a small network is in place based on centroids, and the volumes fluctuate:
Here is are the project files on GitHub if you would like to have a closer look:
• https://github.com/VirtualOrganics/PBD_DynamicFoam_Files
• https://github.com/InteractiveComputerGraphics/PositionBasedDynamics (PDB code)
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VI. The Problem
We took the PBD software from GitHub and modified the Demo example called ‘GenericConstraintsDemos’. All constraints are taken out except the distance constraint, and the simulation is limited to work on a 2D with the intention of extending to 3D eventually.
As you can see in the example, there are nine circles. The simulation allows for any number of circles. The green dots represent the centers of the circles; the red dots represent the centroids of the three adjacent/connected circles; the black dots represent some (outer) intersections between circles; and the blue lines connect either centroids with other centroids, or centroids to intersections in a particular pattern. In the simulation, the radii of the circles can change and, since a distance constraint is applied, the varying sizes of the circles causes the locations (and existence) of the dots and lines to change.
The code at this point is able to identify/calculate the locations of the black dots and the red dots, but he had trouble coming up with an algorithm that correctly connects the red and black dots. The diagram above shows the correct connections, but coming up with an algorithm to do this automatically and as the simulation runs stalled our progress.
So I’m now looking for a developer who can take it to the next level. It doesn’t necessarily need to be in PBD an other Physics Engine (Blender-Bullet-PBD) might do the job, one where on top of the physics-interactions a network-formula can balance out the weights and regulate the system.
All suggestions and questions are more than welcome!
Best,
m.