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Along with the pRender node, this is the only other node that’s absolutely required to create a
particle system.
pEmitter nodes have four parameters tabs:
– Controls: The primary controls governing how many particles are generated (Number), how long
they live (Lifespan), how fast they move (Velocity) and how widely distributed they are (Angle and
Angle Variance), their rotation (Rotation Mode with X, Y, and Z controls), and whether there’s spin
(Spin X, Y, and Z controls). For each parameter of particle generation, there’s an accompanying
Variance control that lets you make that parameter less uniform and more natural by introducing
random variation.
– Sets: This tab contains settings that affect the physics of the particles emitted by the node. These
settings do not directly affect the appearance of the particles. Instead, they modify behaviors such
as velocity, spin, quantity, and lifespan.
– Style: While the Controls tab has a simple control for choosing a color for particles, the Style
tab has more comprehensive controls including color variance and Color Over Life controls.
Additionally, size controls including Size Over Life, fade controls, and blur controls let you create
sophisticated particle animations with a minimum of adjustments, while Merge controls give you
an additional level of control over how overlapping particles combine visually. A set of controls at
the bottom lets you choose how animated effects are timed.
– Region: The Region tab lets you choose what kind of geometric region is used to disperse
particles into space and whether you’re emitting particles from the region’s volume or surface.
The Winding Rule and Winding Ray Direction controls determine how the mesh region will handle
particle creation with geometric meshes that are not completely closed, as is common in many
meshes imported from external applications. Tweaking these last parameters is common when
using imported mesh geometry as a region for emitting particles, since even geometry that
appears closed will frequently appear to “leak” particles thanks to improperly welded vertices.
Forces
Many of the particle nodes found in the Particles bin of the Effects Library are “forces” that enhance a
particle simulation by simulating the effect of various forces acting upon the particles generated by
an emitter.
Some forces, including pDirectionalForce, pFlock, pFriction, pTurbulence, and pVortex, are rules that
act upon particles without the need for any other input. These are simply “acts of nature” that cause
particles to behave in different ways.
Other forces, such as pAvoid, pBounce, pFollow, and pKill, work in conjunction with 3D geometry in a
scene such as shapes or planes to cause things to happen when a particle interacts or comes near
that geometry. Note that some of the particles described previously can also use geometry to direct
their actions, so these two categories of forces are not always that clear-cut.
Compositing
The pMerge node is a simple way to combine multiple emitters so that different types of particles work
together to create a sophisticated result. The pMerge node has no parameters; you simply connect
emitters to it, and they’re automatically combined.
Rendering
The pRender node is required whether you’re connecting a particle system’s output to a 2D Merge
node or to a Merge3D node for integration into a 3D scene. Along with the pEmitter node, this is the
only other node that’s absolutely required to create a particle system.
– Controls: The main controls that let you choose whether to output 2D or 3D image data, and
whether to add blur or glow effects to the particle systems, along with a host of other details
controlling how particles will be rendered.
Chapter 87Particle Systems 1588
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