Particle Systems Lecture Notes 2
syllabus | schedule | assignments | ARTC courses
Software Rendered Particles
You have to have a light in the scene; you have to apply a material to the particles.

Blobby - Called metaballs - is attracted to meld with nearby particles
      Radius - size of sphere
      Threshold - how attracted it is to the nearby particles;
            1 = maximum attraction; 0 = none
      May need to increase Radius as you increase Threshold

Clouds - Already has the defaultParticle Shader attached, also a metaball
      Better Illumination - increases self shadowing
      Radius - size
      Surface Shading - 0 = cloudier effect; 1 = more distinct clouds
      Threshold - how much they melt together

Tube - can be tapered, must have a volumetric shader like particle cloud on it.
      Radius0 - starting radius
      Radius1 - end radius
      Tail Size - length of tube (is multiplied by velocity) faster = longer tail

Rendering Tip: To render without particles, select particles -> Attribute Editor under Render
Stats: Turn Primary Visibility OFF

Lighting Tip: Cloud, Tube, and Blobby need lights in the scene. Point, Multipoint, Streak, and Multistreak can also use the lights in a scene - all others do not.
Particle Emitters
Emitters - generates particles, can be moved, and keyframes set, can parent or group them to moving objects, can have stand alone emitter or an emitter can be added to an object

Creating Emitters (positional)

      Particles -> Create Emitter (don't have anything selected)
            particle object is created and connected to the emitter

      Click Play to see them in action

Creating Object Emitter - the default is omnidirectional

      Select the geometry

      Particles -> Emit from Object
            particle object is created and connected to the emitter

To emit from CVs or edit points

      Select Component - pick the points or CVs you want to emit from
      Particles -> Emitter from Object

If you want to Duplicate an Emitter be sure to select Upstream Graph so it gets its particles

Deleting an Emitter does not delete the particles - you must do this manually.
      Look in the Outliner

Create Emitter Options

      Emitter Name - give it a name
      Emitter Type - omni, directional, volume
      Emitter Attributes (Emission Attributes in the Attribute Editor)

      Rate - how many particles per second are born

      Direction/Distance Attributes
            Max Distance - how far away from the emitter are particles emitted

            Min Distance - how close to the emitter are particles born
            (it always randomly gives birth to particles between min and max)

            Direction (only for directional emitters) XYZ

            Spread - particles are randomly distributed in this cone area.
                  1 = 360 degrees      .5 = 180 degrees      .33 = 120 degrees
            For Directional Only

      Basic Emission Speed Attributes:
            Speed - how fast they move

Emit from Object Options
      Point Emitter - emits from cvs, edit points, points on a surface or particles
            (select just the CVs using the select component tool
      Surface Emitter - emits from the surface of an object (object emitter)
      Curve Emitter - emits from random positions on the curve

      Scale Rate by Object Size - change it in relationship to the object size

Connecting 2 different particles to the same emitter:

Prep: Make an emitter

Making an empty particle object:

      In the Particle Options box enter 0 into the number of particles
      Name the emitter
      Move the cursor to the workspace and hit enter

Connecting the particles to the emitter:

      Windows - Relationship Editors - Dynamic Relationships
      Select your empty particle set
      Click Emitter
      Select the emitter you want to connect to and close the window
Dynamic Relationship Editor
Select Window menu - Relationship Editors - Dynamic Relationships

Selection Modes - Fields - Collisions - Emitters - All

On the left side, select the particles or object

As you click each selection mode you will see what is already connected

The list contains things that can be connected to the particle or object

Click something on the list to connect it to the item selected in the list on the left
Fields
Fields are forces that are used to animate particles and soft and hard body objects.

Two kinds: Stand Alone and Fields attached to objects

To make a stand alone field and connect it to a set of particles:
      Select Particles
      Fields -> fieldname

To add a field to an object:
      Fields -> fieldname
      Make a sphere
      Select the object and the field
      Fields -> Use Selected as Source of Field

In Dynamics Relations Editor connect the field to some particles

To delete a Field - in Outliner:
      Open the plus sign near the field object
      Select and Delete the Field

To add multiple fields to a set of particles
      In Dynamics Relations Editor select the particles then add as many fields as you want

Air Field - particles are accelerated or decelerated to match the speed of the air
      Can parent the field to something moving or have it as an object field or animate the field itself

Predefined Settings - Wind, Wake and Fan

      Wind - default = X axis at 5 units per frame

      Wake - good for adding a field to a moving object and when the object moves through
      a particle object it will move the particles (it only works with the object moving)
      Can keyframe the object or the field or can parent the field to the object

      Fan - default = 45 degrees spread along X at 5 units per frame, Inherit Velocity = 1.0

Air Field Attributes:
      Airfield Name - name it
      Magnitude - strength of the airfield
            magnitude and direction = velocity
            positive number pushes particles and negative number attracts particles
      Attenuation - how the strength changes as you get further from the effected particles
            0 = constant over distance, # must be between 0 and 1
      Direction - XYZ
      Speed - how fast the particles match the velocity of the airfield
            0 = particles will never match the velocity (airfield OFF)
            1 = instantly match the velocity
      Inherit (Velocity) - Only for air which is parented to a moving object -
            will come up with an average of the velocity of the moving object and the velocity of the air field
      Inherit Rotation - airflow will rotate if object or airfield is rotating
            Wind and Fan are ON by default

      Component Only -
            OFF - applies whatever force necessary to make particles match velocity of air
            ON - the particles continue moving in the same direction after the field has past
      Spread - Enable Spread - Use the spread Angle or Not
            ON = Only a cone like area of the field effects the particles
            OFF = all the particles within Max Distance are effected
      Distance - Use Max Distance
            Use ON = particles have to be within a certain distance to be effected
            Max Distance - max distance from the force that things are effected
      Special Effects - Apply per Vertex - ON = each CV of the obj exerts force equally
            OFF = force is exerted from the center of the object


Open the Help Menu and check out Library -> Dynamics -> 3 Fields -> Air Field

Drag Field - exerts a braking or friction force to the particles
      * create an animated drag field that affects an emitted set of particles

Gravity Field - simulates earth's gravity
      * add gravity to the above simulation

Newton Field - pulls particles towards others with a force independent of the mass of the object exerting the force
      (Newton's Law of Universal Gravitation) - as things get further away there is less pull.
      * create an animated Newton field that affects an emitted set of particles

* Exercise: Create an animated field that effect some particles using each of the following:

Radial Field - Like a magnet - pulls or pushes away.

Turbulence Field - causes irregular motion in the particles - like jitters or waves.

Uniform Field - pushes objects uniformly in a single direction.

Vortex - pulls particles in a circular direction like a whirlpool or tornado.
Hardware Rendering
Window - Rendering Editors - Hardware Render Buffer

Choose your camera from the Cameras Menu

Render - Attributes:
      Filename
      Pick an extension type
      Set start and end frame
      Pick TIF for Image Format
      Resolution - click Select and pick 720 x 480
      Alpha Source should be Hardware Alpha or Luminance
      Lighting Mode should be Default or All Lights
      Draw Style Smooth Shaded
      Select Texturing
      Select Geometry Masking only when you don't want it to render your geometry

* The Full Image Resolution is only for when your image goes beyond the size of the screen

Multi-Pass Render Options
      Can turn on Multi Pass Rendering but it take considerably longer to render
      (this softens the look of the rendering)

Display Options:
      Turn ON or OFF icons to have them show or not show in your scene

Render - Test Render a few frames using the timeslider to select the frame first
      (can use the little icon in the playback area)
      Render Sequence when you are ready
      (do not move any window in front of the Hardware Render Buffer when it is rendering)

Flipbooks - choose your rendered Flipbook from the menu
      (it plays back once slow then after that it is fast)