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Particles are lots of items emitted from mesh objects, typically in the thousands. Each particle can be a point of light or a mesh, and be joined or dynamic. They may react to many different influences and forces, and have the notion of a lifespan. Dynamic particles can represent fire, smoke, mist, and other things such as dust or magic spells. Static particles form strands and can represent hair, grass and bristles. You see particles as a Particle modifier, but all settings are done in the Particle sub-context of the Object context (F7).

Particles do not work with an Array modifier or with Group objects, it is planed to change that with version 2.5.

Incompatibility with Prior Versions
There are many differences between the “old” particle system that was used up to and including version 2.45, and the “new” particle system. There are many things possible now that could not be done with the old system. The new system is incompatible to the old system, though Blender tries to convert old particle systems, which works only to some extent. The old system is most like the new Emitter system (keep reading to find out what that is). If you are using an old version of Blender 2.45 and previous, click here to access the old documentation.


Description

Image 1: Some fur made from particles (Blend file).

Particles generally flow out from their mesh into space. Their movement can be affected by many things, including:

  • Initial velocity out from the mesh.
  • Movement of the emitter (vertex, face or object) itself.
  • Movement according to “gravity” or “air resistance”.
  • Influence of force fields like wind, vortexes or guided along a curve.
  • Interaction with other objects like collisions.
  • Partially intelligent members of a flock (herd, school, …), that react to other members of their flock, while trying to reach a target or avoid predators.
  • Smooth motion with softbody physics (only Hair particle systems).
  • Or even manual transformation with Lattices.

Particles may be rendered as:

  • Halos (for Flames, Smoke, Clouds).
  • Meshes which in turn may be animated (e.g. fish, bees, …). In these cases, each particle “carries” another object.
  • Strands (for Hair, Fur, Grass); the complete way of a particle will be shown as a strand. These strands can be manipulated in the 3D window (combing, adding, cutting, moving, etc).

Every object may carry many particle systems. Each particle system may contain up to 100.000 particles. Certain particle types (Hair and Keyed) may have up to 10.000 children for each particle (children move and emit more or less like their respective parents). The size of your memory and your patience are your practical boundaries.

You can have multiple sets of particle systems attached to an object, so, for example, you can have long fur as one system, and then very short fur mixed in. These particle systems can be mixed and matched and shared among many objects in your blend file.

The “new” system is much more powerful than the old, but there is one thing you can’t do with the “new” system: you may no longer create branched static particle systems e.g. for very simple shrubbery.

Workflow

The process for working with particle is:

  1. Create the base mesh which will emit the particles. This mesh is not rendered by default, but the base material for the mesh is used to color the particles. Since a mesh can carry multiple materials, each particle system may have its own material.
  2. Create one or more Particle Systems to emit from the mesh. Many times, multiple particle systems interact or merge with each other to achieve the overall desired effect.
  3. Tailor each Particle System’s settings to achieve the desired effect.
  4. Animate the base mesh and other particle meshes involved in the scene.
  5. Define and shape the path and flow of the particles.
  6. (Only applies to Hair particle systems): Sculpt the emitter’s flow (cut the hair to length and comb it for example).
  7. Make final render and do physics simulation(s), and tweak as needed.


Creating a Particle System

Image 2: Adding a particle system.

To add a new particle system to an object, go to the Particle sub-context of the Object (F7) context and click Add New in the Particle System tab. An object can have many Particle Systems. Therefore, when adding a Particle system, you may also:

  • Select an existing particle system from the drop-down menu next to the Add New button.
  • Advance the active particle system (X Part Y) selector to an empty slot by clicking it near its right edge. As with

material indices, the number to the left of Part indicates the active particle system, while the number on the right indicates the number of particle systems available for the object.

  • Switch between already assigned Particle systems (X Part Y).
  • Exchange one particle system for an other (for example PA:PSys.002 to PA:PSys.001)


Types of Particle systems

Image 3: Particle system types.

After you have created a particle system, the Buttons window fills with many panels and buttons. But don’t panic! There are three different types of particle systems, and you can change between these three with the Type drop-down list:

Emitter
This parallels the old system to the greatest extent. In such a system, particles are emitted from the selected object from the Start frame to the End frame and have a certain lifespan. You may also render these kind of particles as strands (depending on the particle’s physics).
Reactor
Reactor particles are born when other systems’ particles do things. Usually, but not with emit from particles, the target particle’s size determines it’s area of influence. This is useful for most of the effects where you would have used children in the old particle system.
Hair
This system type is rendered as strands and has some very special properties: it may be edited in the 3D window in realtime and you can also animate the strands as Softbodies (similar to Softbody curves).

The settings in the Particle System panel are different for each system type. For example, in Image 3 they are shown for only system type Emitter.

Common Options

Each system has the same basic sets of controls, but options within those sets vary based on the system employed. These sets of controls are:

  • Particle System - basic controls about quantity and quality.
  • Physics - how the particles behave.
  • Visualization - how to see the particles, in the 3D viewport and when rendered.
  • Extras - controlling emission, interaction and time.
  • Children - particles spawning more particles.

Some individual settings are common for more than one particle system:

  • Datablock selector (PA:): here you can select particle systems (browser button), name them (text field), or delete them (X button).
  • X Part Y: selector for the active particle system.
  • Enable buttons: toggle for enabling or disabling the active particle system in the 3D window or the rendering.
  • Type: menu for selecting the type of particle system.


Interaction in real time

To work with particle systems you may find it handy to use the Timeline window. You can change between frames and the particle system will always be shown in the actual state. The option Continue Physics in the Playback menu of the Timeline window lets you interact in real time with the particle system, e.g. by moving collision objects or shake an emitter object. And this is real fun!

Blender3D FreeTip.gif
Continue Physics does not work while playing the animation with AltA
Right. This works only if you start the animation with the Play button of the Timeline window.


Two notes at the end:

  • For renderfarms, it is best to bake all the physics systems, and then copy the blendcache to the renderfarm as well.
  • Be careful with the sequence of modifiers in the modifier stack (as always). You may have a different number of faces in the 3D window and for rendering (from v2.47 upwards), if so, the rendered result may be very different from what you see in the 3D window.

We will continue with an overview over the three different particle system types.

Links

Author’s Note
I have written the text and created the images for the german manual [1] --Soylentgreen 19:53, 4 February 2008 (CET)
I've taken quite a lot of text from BlenderDev/Particles_Rewrite_Doc and from [2]. So who is to be credited for that and in what form? --Soylentgreen 20:13, 5 February 2008 (CET)