From BlenderWiki
If you are using a version of Blender up to 2.45 click here to access the old documentation.
Particles, Soft Bodies and Cloth objects may collide with mesh objects. Boids try to avoid Collision objects.
- The objects need to share at least one common layer to have effect.
- You may limit the effect on particles to a group of objects (in the Extras panel).
- Deflection for softbody objects is difficult, they often penetrate the colliding objects.
- Hair particles ignore deflecting objects (but you can animate them as softbodies which take deflection into account).
If you change the deflection settings for an object you have to recalculate the particle, softbody or cloth system (Free Cache), this is not done automatically. You can clear the cache for all selected objects with CtrlB → Free cache selected.
Mode: Object Mode
Panel: Object context → Physics sub-context → Collision
Hotkey: F7
Options
Particle Interaction
- Kill
- Ends the “life” of colliding particles.
- Damping
- Damping during a collision (independent of the velocity of the particles). Can be animated with Object Ipos, RDamp channel (obviously, there is a mistake naming the curves).
- Rnd damping
- Random variation of damping. Can be animated with Object Ipos, Damping channel.
- Friction
- Friction during movements along the surface.
- Rnd friction
- Random variation of friction.
- Permeability
- Fraction of particles passing through the mesh. Can be animated with Object Ipos, Perm channel.
Soft Body and Cloth Interaction
- Inner
- Size of the inner collision zone (padding distance).
- Outer
- Size of the outer collision zone.
Outside and inside is defined by the face normal, depicted as blue arrow in (Image 1b).
- Damping
- Damping during a collision.
- Ev. M. Stack
- The modifier stack is evaluated first, then the collision is calculated. Enabling this is important if you want to take the SubSurf modifier into account (or don’t, because this may be really time extensive).
Softbody collisions are difficult to get perfect. If one of the objects move too fast, the soft body will penetrate the mesh. See also the section about Soft Bodies.
Effector Interaction
- Absorption
- A deflector can also deflect effectors. You can specify some collision/deflector objects which deflect a specific portion of the effector force using the Absorption value. 100% absorption results in no force getting through the collision/deflector object at all. If you have 3 collision object behind each other with e.g. 10%, 43% and 3%, the absorption ends up at around 50% (
100×(1-0.1)×(1-0.43)×(1-0.03)).
Examples
Here is a Meta object, dupliverted to a particle system emitting downwards, and deflected by a mesh cube:
Hints
- Make sure that the normals of the mesh surface are facing towards the particles/points for correct deflection.
- Hair particles react directly to force fields, so if you use a force field with a short range you don’t need necessarily collision.
- Hair particles avoid their emitting mesh if you edit them in Particle mode. So you can at least model the hair with collision.
