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Particle FX for DAZ|Studio

Velocity and Nozzle Direction

When used in a Source Action the Set Velocity sets the initial velocity of the particles.

When used in a Flow Action the Set Velocity can change the particles velocity or speed each time frame, making them appear to speed up, slow down or change direction.  

The Set Type has three options, Set and  Add,  which tell whether the Operator sets the particles velocity or adds to its current velocity.

Speed sets the speed that will be applied to the particles.  The units are centimeters per second.  

 Speed Range is the amount the speed will be randomized.

A particles velocity consists of a speed and a direction.  To go with the Speed parameter the Set Velocity needs a Direction to completely define a particle's velocity.

If the Operator does not have a Direction, then it will only affect the speed of the particle, not the direction it is traveling.  This can be used in Flow Actions to slow down or speed up the particle.  

The Set Velocity is often paired with a Nozzle Direction.  

The Nozzle Direction acts like a hose nozzle, spreading the direction of the particles out over an angle set by the Width Parameter. 

The Inner Radius Parameter is a percentage of the Width.  By setting it large it hollows out the nozzle so that the particle directions are all closer to the Width value.  For effects that occupy large volumes it may not be necessary to fill the volume with particles but only the outer edges. 

Since the Direction can be scaled and rotated, it has the standard scene node  Rotate and Scale dials visible.

The Nozzle will appear in the scene as cone shaped nozzle to give a visual cue as to the direction the Nozzle is pointing.  The object can be hidden by setting the Visibility of the Nozzle Direction to Off.  

The Parent To allows the Domain to be parented to another node in the scene or even the ground (the None selection).   

The Width parameter sets the spread of the spray.  Setting this to 180 will make a omnidirectional spread.  

The Inner Radius can used to hollow out the spray.  Some effects don't need the interior of the spray filled in with particles allowing the number of particles to be reduced.

The Set Velocity operator can operate in two time modes, Scene Time and Particle Time.  

When in a Source Action the Operator automatically runs in Scene Time.  Any keyframing of the Operators dials are applied normally.  Since an Operator in a Source Actions would apply the initial rotations to a particle, this allows the starting behavior of the particle stream to be varied over time and animated.  In a Flow Action using Scene Time  would allow the effect to set all the particles velocities in a synchronized manner if so desired.   

A Set Velocity Operator in a Flow Action can be set by the constructor script to operate in Particle Time.  In Particle Time the keyframing of the dials is biased to the birth time of the particle.  The keyframes can be set as is usually done but the affect will be applied as if the zero time on the Timeline Tab is the particle's birth.

When operating in Particle Time the velocity of the particle can be controlled over time.  

When operating in particle time,  at each frame  the velocity specified by the Speed parameter and Direction is added to the particle's velocity.  

See the HTML help file for the effect to see what time its operators are running on.  Unless otherwise stated, it is assumed that Set Velocity Operators in Flow Actions are running on Particle Time.  

Since the time mode is set by the effect constructor the user will not have to be worried about setting or modifying it.

Many effects can be made to appear more or less dynamic by changing the Speed Range and the Speed Randomizer.   A Speed Range of 10% is usually a good starting point.

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