I don’t want these particles out side of my object: .blend file
The problem is that I’ve already got two transparent planes and it will get all messy if I add others to stop the particles from getting out.
This is mostly because there are gaps between the cylinders and the curved meshes. Also, you should probably apply the solidify modifiers you are using.
Normally, what I would do is duplicate all the enclosing meshes and use parts of these to make one collision object to keep the particles in but a quicker way is to just use planes and block off these gaps. Planes are rather thin however and not very good collision objects, you should join these together into one object to create a boxlike enclosure.
Make sure the planes intersect the other meshes slightly so that there are absolutely no gaps left for the particles to escape. To make ones for the cylinders as tight as possible, just duplicate the tops, separate it and scale it outwards.
If you have the time, a much better collision object would be something in the shape of your actual model(s) to make sure that the space inside is as closed as possible.
You could try to increase the
Subframes in the particle system's physics properties. This will increase amount of times particle collisions are calculated per frame, increasing the chance that they will collide with the wall.
However, a plane is an infinitely thin wall, which is not natural. The collision detection calculations probably needs some thickness. I'd really recommend using some thickness. May you can get away with applying the
solidify modifier to your plane(s).