Fields

Fields are forces that are used to animate particles and other dynamic objects.

Three kinds: Stand Alone, Object Fields, Volume Fields

1. Stand Alone - not owned by any object - can be sitting still or moving

2. Object Fields - the field can eminate from the curves, polygon or NURBs surfaces, particles, lattices or curves. You can select Edit Points (EPs), Control Vertices (CVs), surfaces, particle objects, etc.

3. Volume Fields - this allows you to select a shape to specify the area in which the field has any effect. Things within this area are affected and things outside this volume are not.


To attach a field to an nParticle when making the field:
     
      1. Select Particles (can be more than one set)

      2. Fields/Solvers menu - fieldname (Gravity or Newton, etc.)

      ***This is a Stand Alone field but dynamically connected to the particles

OR

1. Select the particles and the stand alone field and select Fields/Solvers menu - Assign to Selected

To add a field to objects - (Object Field):

      1. Make a stand alone field - Fields/Solvers menu - fieldname - Ex: make turbulence

      2. Make a object (polygon, NURBs, particles) - ex: make a sphere

      3. Select the field and then the object

      4. Fields/Solvers menu - Use Selected as Source

5. Look in the Outliner under the + and see that the field has been parented to the object.

6. Make some particles by Sketching them with the nParticle Tool

7. Animate the ball going into the particle set.

8. Change the Nucleus so Gravity and Air Density are 0

9. Now we need to connect the Particles to the Field using the Dynamic Relationship Editor (see below)


Dynamics Relations Editor

Windows - Relationship Editor - Dynamic Relationships

Select the particles on the left first

Click a Selection Mode second: Fields, Collisions, Emitters or All

The blue bar indicates they are connected. You can click it to turn it on or off.

10. Select the turbulenceField1 and Rewind - Play

11. Close the Dynamic Relationship Editor window

12. Open the Attribute Editor for the TurbulenceField and alter the Magnitude


To make a Volume Field

1. Select the particles you want to be affected

2. Fields/Solvers menu - pick Turbulance Options

3. Select the Volume shape

4. Make sure the volume is partially over the particles by looking in the 4 windows and scaling it to be bigger.

5. Increase your turbulance magnitude. Play and tweak till you get it right.



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.


Next Lecture: [Per Particle Array]