Editing Particle system (section)

== Particle system taxonomy ==
In 1983, Reeves defined only animated points, creating moving particulate simulations — sparks, rain, fire, etc. In these implementations, each frame of the animation contains each particle at a specific position in its life cycle, and each particle occupies a single point position in space. For effects such as fire or smoke that dissipate, each particle is given a [[fade (filmmaking)|fade out]] time or fixed lifetime; effects such as snowstorms or rain instead usually terminate the lifetime of the particle once it passes out of a particular [[field of view]].<ref name="reeves"/>

In 1985, Reeves extended the concept to include rendering the entire life cycle of each particle simultaneously, the result transforms particles into '''static''' strands of material that show the overall trajectory, rather than points. These strands can be used to simulate hair, fur, grass, and similar materials. The strands can be controlled with the same velocity vectors, force fields, spawning rates, and deflection parameters that animated particles obey. In addition, the rendered thickness of the strands can be controlled and in some implementations may be varied along the length of the strand. Different combinations of parameters can impart stiffness, limpness, heaviness, bristliness, or any number of other properties. The strands may also use [[texture mapping]] to vary the strands' color, length, or other properties across the emitter surface.<ref>{{cite journal |last1=Reeves |first1=William T. |last2=Blau |first2=Ricki |title=Approximate and probabilistic algorithms for shading and rendering structured particle systems |journal=ACM SIGGRAPH Computer Graphics |date=July 1985 |volume=19 |issue=3 |pages=313–322 |doi=10.1145/325165.325250}}</ref>

In 1987, Reynolds introduces notions of [[Flocking (behavior)|flocking]], [[herding]] or [[Shoaling and schooling|schooling]] behaviors. The '''[[Boids|boids model]]''' extends particle simulation to include external state interactions including goal seeking, collision avoidance, flock centering, and limited perception.<ref>{{Cite book
 | last1=Reynolds
 | first1=Craig
 | title=Proceedings of the 14th annual conference on Computer graphics and interactive techniques
 | chapter=Flocks, herds and schools: A distributed behavioral model
 | date=1987
 | author1-link=Craig Reynolds (computer_graphics)
 | year=1987
 | publisher=[[Association for Computing Machinery]]
 | pages=25–34
 | isbn=978-0-89791-227-3
 | doi=10.1145/37401.37406
 | citeseerx=10.1.1.103.7187
 | s2cid=546350
 }}</ref>

In 2003, Müller extended particle systems to [[fluidics]] by simulating [[viscosity]], [[pressure]] and [[surface tension]], and then rendered surfaces by interpolating the discrete positions with [[Smoothed Particle Hydrodynamics]].<ref>{{cite journal
| vauthors   = Müller M, Charypar D, Gross M
| date       = 
| title      = Particle-Based Fluid Simulation for Interactive Applications
| url        = https://matthias-research.github.io/pages/publications/sca03.pdf
| journal    = SIGGRAPH Symposium on Computer Animation 
| volume     = 
| issue      = 
| pages      = 
| doi        = 
| pmc        = 
| pmid       = 
| access-date = 2022-01-18
}}</ref>

{{multiple image
| align             = center
| image1            = Particle Emitter.jpg
| width1            = 220
| caption1          = A cube emitting 5000 animated particles, obeying a "gravitational" force in the negative Y direction
| image2            = Strand Emitter.jpg
| width2            = 220
| caption2          = The same cube emitter rendered using static particles, or strands
}}