Building a Particle System

References:1. Gamasutra article by Van der Berg2. Particle System API by McAllister3. Explosion.c

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Particle System (PS) Gallery

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Performance and Requirement

Keep in mind: a PS greatly increases the number of polygon per frame (one particle: four vertices & 2 triangles)Perform as few memory operations (allocation/release) as possible Use a flag to mark a particle dead or respawn

Ability to link PS within the hierarchy of other geometry (smoke out of a cigarette)

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Data Structure

Reference 1 contains all other detailsReference 1 contains all other details

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Explosion

A simple particle system demo for explosion effects (particles and debris)Observe how particle evolves and how debris rotates

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Particle System API (McAllister)

API used in some academic projectsDesign modeled after OpenGLDesign goals: Run-time efficiency Flexibility: create effects from simple

building blocks (gravity, bounce, …) Scalable simulation quality Easy to learn

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API Description

Particle Position Velocity Color Alpha Size Age Secondary position Secondary velocity

Particle group A set of particles acted

upon by the same forces API applies to the

current group

Action Functions modify the

attributes of particles in the current group

Currently has 27 actions (some are physically related)

Building blocks for special effects

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Actions in Use

ActionList Actions compiled (si

milar to displaylist)

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Attributes and Domains

API state (color, velocity, size, …)pSource: create new particles

Domain: a uniform mechanism for specifying a region of three-space

pColorD: a region of color space

pVelocityD: a region of vector space

A variety of shapes: PDSphere, PDPlane, …

Specified by 9 or fewer floats

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Particle Simulation

Newton’s lawUse Euler’s method with user-specified step size dt

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Design a PS that suits your needs

Starting posBreaking posTimeline: ADSR envelopeColor attributesRendering styleDynamics

PAPI (v.210)

You need VC80!Uses freeglut

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Particle Data Structure

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Example: ParticleContext_t PGenParticleGroups

P_group_count Max_particles (similar to display list)

CurrentGroup Current particle group all

actions and commands apply

SetMaxParticlesGetGroupCount

# of particles in the groupGetParticlePointer

Expose internal storage of particles (avoid copying for higher performance)

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GetParticlePointer

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ParticleContext_t P

GravityMove (vel, rotvel)

Update pos, orient (up vector)

P.Source (rate, dom) Particles to add per unit

timeP.Sink (inOrOut, dom)

Kill particles w.r.t dom

Bounce (friction, resilience, cutoff, dom)

Sphere, rectangle, triangle disc, plane

Color (rgb); Color(dom)

Translate pos into color

Velocity (dom) …

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pDomain

Blob, Box, Cone, Cylinder, Disc, Line, Plane, Point, Rectangle, Sphere, Triangle