Particle Systems and Dynamics

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Particle Systems and Dynamics

• IM209
• Eunjoo Lee

2
Further Reading

• Chapter 14, Maya 4.5 Fundamentals, New Riders,
  2003
• Tutorial
• Chapter 14 in Maya 4.5 Fundamentals

3
Learning Objectives

• Creating rigid-body dynamics simulations
• Applying forces
• Applying constraints
• Creating particles
• Particle types
• Creating soft-body dynamics

4
Rigid-Body Dynamics

• The Objects are given mass and (optionally)
  initial velocities and spin.
• Then you apply forces that can affect the
  objects.
• If objects collide, they can deflect based on the
  mass and friction levels assigned to them.

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Active and Passive Bodies

• Maya has two kinds of rigid bodies - active and
  passive.
• An active rigid body reacts to dynamics-fields,
  collisions, and springs-not to keys.
• A passive rigid body can have active rigid bodies
  collide with it. You can key its Translate and
  Rotate attributes, but dynamics have no effect on
  it.
• For instance, to bounce a ball on a floor, you
  would make the ball an active rigid body because
  it needs to fall with gravity and rebound after
  colliding with the floor. You would make the
  floor a passive rigid body so it doesn't careen
  away from the ball when the ball bounces off it.

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Create a Rigid Body

• To create a rigid body from a single object
• Select the object
• Select Soft/Rigid Bodies gt Create Active Rigid
  Body
• To create a rigid body from several objects
• Group the NURBS or polygonal objects under a
  parent node. For instance, select the objects and
  select Edit gt Group.
• Select the group node.
• Select Soft/Rigid Bodies gt Create Active Rigid
  Body. Or
• Select Soft/Rigid Bodies gt Create Passive Rigid
  Body.

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Dynamics settings

• Mass The weight of the object
• Bounciness The amount of energy retained after a
  collision
• Damping An effect that produces a drag on an
  object. Values higher than 0 make the object lose
  directional and angular momentum over time.
• Static Friction The amount of energy to move an
  object
• Dynamic Friction The amount of energy to keep an
  object moving
• Stand In To reduce calculation time it uses
  simple objects

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Tutorial Ten Pin Bowling

• Working Unit meter
• Create a polygon sphere for a ball
• Create a polygon sphere for a pin
• Adjust vertices to shape as a pin

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Tutorial Ten Pin Bowling

• Select a ball
• From menu, Dynamics mode, Soft/Rigid Bodies
  Create Active Rigid Body
• Set attributes for a ball from Channel Box
• Initial velocity (Z) -150
• Initial Spin Z 366
• Mass 15
• Bounciness 0.6
• Static Friction 0.1
• Dynamic Friction 0.1
• Active on
• Collisions on

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Tutorial Ten Pin Bowling

• Select a pin
• From menu, Dynamics mode, Soft/Rigid Bodies
  Create Passive Rigid Body
• Set attributes for a pin from Channel Box

• Center of Mass (Y) 100
• Impulse Z 10
• Spin Impulse Y 2
• Spin Impulse Z 10
• Mass 7
• Bouciness 0.1

• Damping 0.1
• Static Friction 0.2
• Dynamic Friction 0.2
• Active on
• Collisions on

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Tutorial Ten Pin Bowling

• Duplicate multiple pins and place them as
  follows. Play your movie.

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Tutorial Ten Pin Bowling

• All values are approximation. You can improve
  animation by changing all values.
• Play with all attributes for Rigid Body
• Understand the effect of mass, bounciness and
  damping

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Fields

• Stand-alone fields
• It influence objects from a stationary or moving
  position in the workspace. A stand-alone field is
  not owned by geometry.
• Object fields
• Object fields are owned by an object and exert
  influence from the object. An object can own
  multiple fields.
• Volume fields
• You can select a volume to define the region in
  space in which particles or rigid bodies are
  affected by any field in Maya. The volume shapes
  you can use are cube, sphere, cylinder, cone, and
  torus.

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Fields

• Air A push type of field, it comes with presets
  for Wind, Wake, and Fan.
• Drag A field that slows the motion
• Gravity It causes objects to move and accelerate
  in a given direction
• Newton Similar to gravity, but operates in a
  spherical manner
• Radial Like Newton, but does not take mass into
  account
• Turbulence It is applied to soft bodies or
  particles to create the impression of wind or
  waves
• Uniform A field that pushes objects in a given
  direction
• Vortex A kind of rotating gravity
• Volume Axis A complex field that lets you
  specify a volume shape

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Creating fields

• To create a stand-alone field and connect objects
  to the field
• Select the objects you want the field to affect.
• Select Fields gt fieldname
• The field is created at the origin and everything
  you've selected is connected to it. You can move
  the field icon away from the origin to change the
  range and direction of influence.
• Click the play button to see the field affect the
  connected objects

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Creating fields

• To add a field to an object and connect objects
  to the field
• Select Fields gt fieldname to create the field. If
  it's already created, select the field.
• Ctrl-select the object (or objects) to which you
  want to add the field.
• Select Fields gt Use Selected as Source of Field
  to add the field to the object.
• By default, most fields are added to all CVs or
  vertices of the object. The field emanates from
  each point with equal strength. See the field's
  Apply Per Vertex attribute description for more
  details.
• In the Outliner, select the objects you want the
  field to influence and Ctrl-select the field.
• The field is indented under the owning object.
• Select Fields gt Affect Selected Object.
• Click the play button to see the field influence
  the connected objects.

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Creating fields

• To create a volume field
• Select the objects you want the field to affect.
• You can select particles, rigid bodies, or soft
  bodies.
• Select Fields fieldname gt .
• In the field's options window, from the Volume
  Shape pulldown, select a shape (other than None).
  
• None means the field affects all the particles to
  which is connected.
• Set the volume field attributes as desired.
• Click Create.

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Fields - Air

• An air field simulates the effects of moving air.
• You can parent an air field to a moving object.

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Fields - Gravity

• Select the object.
• Key the object's Translate and Rotate attributes
  to give the object motion.
• At the first frame of keyed motion, select
  Soft/Rigid Bodies gt Set Passive Key.
• This keys the Active attribute to the off setting
  and keys the object's current Translate and
  Rotate attribute values.
• At the first frame where you want the dynamics to
  have control, select Soft/Rigid Bodies gt Set
  Active Key.
• This keys the Active attribute to the on setting
  and keys the object's current Translate and
  Rotate attribute values.
• Apply the dynamics to the object.
• At a subsequent frame, you can switch control
  from dynamics to Translate and Rotate keys by
  selecting Soft/Rigid Bodies gt Set Passive Key.

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Constraints

• Nail Ties an object to a point
• Pin Two objects that are tied together to a
  separate pivot point
• Hinge Free rotation constrained to an axis
• Spring Elastic movement
• Barrier Blocks objects from going beyond the
  plane it defines

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Particles

• Particles are ideal for animating difficult
  effects, such as aerosol sprays, explosions,
  swarms of bees, and galaxies of stars.
• To create particles you can use drawn particle or
  particle emitters

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Particle Emitters

• Point - omni sprays particles from a point in
  all directions
• Point- directional sprays particles in a given
  direction from a point.
• Volume Particles are created from some point
  within a defined volume
• Surface Nurbs or polygon objects
• Curve Any NURBS curve can emit particles.

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Particle Types

• Hardware rendered
• Window - Rendering Editors - Hardware Render
  Buffer
• Software rendered

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Hardware-Rendered Particles

• Point designed to render as a spot
• Multipoint creates clusters of points to get a
  denser, clumpier appearance
• Streak creates a streaking line
• Multistreak creates clusters of streaks
• Sprites can have a texture and an alpha channel
• Spheres three dimensional spheres
• Numeric displays a number for each particle

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Software-Rendered Particles

• Blobby Surface A particle form of metaballs (eg.
  Drops of mercury)
• Cloud designed to blur and soften the edges of
  blobby surface
• Tube source object is a kind of uncapped
  cylinder
• Instanced Geometry substitutes any sort of
  object for particles.

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Particle Materials and Age

• Each particle has an inherent age (the time since
  it has been emitted)
• You can make particles change colour over the
  course of their lifespan.

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Particle Influences

• Fields All the fields can be set to occur within
  a volume shape or to fall with distance.
• Collisions Any particle system can collide with
  any scene geometry.
• Goals Particles try to move to a specific
  configuration, shape, or location.

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Summary

• Creating rigid-body dynamics
• Caching dynamic animation
• Baking the animation
• Creating particle emitters
• Creating fields
• Creating soft-body dynamics