Particle geometry collision detection ??? Do I need BGE for that?

Support Particles and Physics Simulations
1

Hi there,

I would like to have a geometry applied as an object to particles and thus have the particles collide with each other but use the objects geometry as the collision surface.

Any idea how of if Blender could do this and would I need BGE for that?

2

Here is an image of what I am trying to do.
As you can see the corn kernels overlap and intersect. And I would like them to fill up the space.

You wrote in one thread that the particle system only allows point and sphere collision but not a
custom mesh collision for particle objects.

However when I switch to the BGE in Blender the particle tap goes away and it seems as my
particles also do not emite anymore. I can only make the emitting mesh do something???

Help :wink:

http://f.cl.ly/items/1425250K143Q2o0T3S0Y/particles.jpg
particles.jpg920×910

3

Hey Atom,

I tried to understand what you mean with the particle and single mesh thing.

My main problem I have to figure out is how I could simulate the animation of my kernels. The all pop off the corn in a sequencial order like a spiral vertical down till all are gone. Here is a video so you can see how it goes.

Fluid particles seem not to be an option because it makes the particles sticky.

4

some ideas…

  1. in BGE you need to replicate animation with logic bricks or python… test file here
  2. I would try GSOC bullet build and script here to attempt to transfer your particles to a rigid body simulation… script should be tweaked, have not tested recently
  3. animate a collision plane set to kill particles, or maybe use dynamic paint to displace a subdivided plane as particles collide
5

Thanks for the effort. So it seems to do this I really have to rebuild the kernel emission as single objects and not use a particle system ar snap but it works. I have to investigate this. Thanks again.

6

Here is an example file I dug up that shows the fluid particle system in use. It shows collision and particle stacking. The particles are spheres, however. But your corn kernel is a fairly spherical object so maybe something like this can work. Depends upon how picky you or your client are about the collision.

What the above link was hinting about force fields (described by WiseLyons) is that you can use them to create a buffer zone around your mesh in a spherical shape. It is not perfect, but gives you some ability to prevent obvious intersections.

Attachments

263_particle.fluid.test.04.blend (230 KB)

7

Oh this is not for a client - this is part of my own private artwork. Thank you for the tips. I have to look into both options. Initially I had no luck so far. The self force field kills the nice pop off arc the original animation has and the fluid produces some quite funny and humourus effects. I even set the normal collision to collision without dampering and have a second plane at the ground for dampering.

But I Might need to play more with the different settings.

8

Sorry for hijacking this thread slightly, but with a closely related question I thought it better than starting a new topic.

I too would like to have particles which collide, but my objects are distinctly non spherical. I have a pack of cards, and I would like the 52 objects to be randomly arranged, as if just dropped (or dribbled: http://www.youtube.com/watch?v=QuSsEZbNjvw) onto the table.

Using Newtonian physics for a particle system of cards leads to no stacking, and using fluid physics gives very bizarre results - is this a job for the game engine?

I appreciate that there may be an easier way to achieve the randomness I want, which I am currently looking into.

Thank you in advance for any advice.

9

d401tq bullet GSOC integration is a target to 2.65 so will be around soon, give it a try…
a setup like that should be easy to do, change world settings to improve accuracy

10

Thanks for the advice. I have given it a go in BGE, but had no luck. The (very simple) blend file can be found here: http://goo.gl/4bvXL

What I find is that the objects will drop onto the plane, but will end with some non-zero minimum between them. Is this a ubiquitous flaw in the physics engine, or something that I am doing incorrectly?

Another couple of interesting ‘features’: When I change the collisional bounds from something other than default the behaviour changes very dramatically. Also, I find that the radius of the objects needs to be large enough to partly contain the plane onto which they will fall. In the example file, the upper card has to have a larger radius, otherwise it simply falls straight through.

If anyone more experienced with BGE can give advice I would be very grateful. If this is deemed to be better suited in a separate thread please say!