The Velocity Operator allows conditional speed assignment
to be applied to selected particles based on any other condition or operator
result. Be sure to understand that this operator is conditional. An AlwaysTrue
condtion connected to the ON input data stream of this operator for example,
means that the particle speed will be always set by this operator. You
would then not be able to change the speed of the particles regardless
of any Space Warp or other operator.
ON - (Bool) This input data
stream determines whether the operator is considered 'on' or 'off'. You
can connect other operators to this input channel such as a Bool
Helper to activate/deactivate the whole operator.
Time - (Time) This input data stream is used to define the local
time for the operator when the user wants to override the default system
time.
Particle - (Particle) This input data stream reads in the currently
selected particle group that is to have its speed adjusted. The data stream
MUST be connected and will be highlighted yellow if it
is not.
Position - (Position) This input data stream reads in the currently
selected particle group's position data and can be used to define the
direction for the velocity. A vector is drawn from the current position
to the value that is piped in here. The end result is that this connection
can act as a directional vector.
Velocity - (Velocity) This input data stream reads in a value
to apply as a combined speed + direction setting. Inputting a value into
this data stream overrides the Speed and/or Direction input data streams.
Be aware that the value piped in is dependent upon the selected Type of
control. If only Speed is selected, only the speed part will be taken
into account. The same is true when only Direction or Direction &
Speed are selected.
Type - (Integer) This input data stream takes an integer value
that represents the Type of Velocity method the particles will use. Valid
input values are 0 through 2, where:
Speed - (Speed) This input
data stream is used to override the Speed spinner within the Velocity
rollout.
Speed Variation - (Scalar) This input data stream is used to override
the Variation % spinner within the Velocity rollout.
Direction - (Direction) This input data stream is used to override
the User Direction Axis spinners within the Velocity rollout.
Direction Variation - (Angle) This input data stream is used to
override the Variation Angle spinner within the Velocity rollout.
Evaluation Type - (Integer) This input data stream takes an integer
value that represents the Type of Evaluation method the particles will
use. Valid input values are 0 through 2, where:
Per Second - (Bool) This
input data stream determines whether the Per Second checkbox within the
Velocity rollout is considered 'on' or 'off'. You can connect other operators
to this input channel such as a Bool Helper to activate/deactivate
the whole operator.
No Operator Outputs.
Speed & Direction
- Select this radio button to set the Speed and Direction of the selected
particle group (as piped in through the Particle input data stream). When
the operator affects the selected particles, both the speed of the particles
and the direction they are travelling is changed to match the settings
within this rollout.
Speed - Select this radio button to set the Speed of the selected
particle group only. When the operator affects the selected particles,
just the speed of the particles is changed to match the settings within
this rollout.
Direction - Select this radio button to set the Direction of the
selected particle group only. When the operator affects the selected particles,
just the direction of travel of the particles is changed to match the
settings within this rollout. No speed change is applied.
Speed - This parameter sets the new speed of the selected particles
connected to the input data stream. Be aware that the speed is set to
this value only when the ON input data stream of this operator receives
a True value from another operator or condition.
Variation % - Increase this spinner value to add variation to
the speed of the particles. Higher percentage values make more particles
move at different speeds.
User Direction Axis - The X,Y and Z spinners define a directional
vector in 3D World space. A value of X/Y/Z = 0,0,1 points "up"
from the ground plane, while X/Y/Z = 1,0,0 heads to the right while X/Y/Z
= 0,1,0 points “into” the screen.
Variation Angle - Increase this parameter to cause the selected
particles' trajectories to be randomized. Higher variation angle values
force the particles to deviate from their original trajectory based on
the angle set. So a value of 45 means that a particle's path will be altered
by up to 45 degrees when the Velocity operator becomes active.
The Velocity operator has two special input data streams, Direction
and Velocity. Any condition or operator may modify these
inputs based on various rules. One example would be that one operator
changes the speed of a particle group based on the distance to an object
in the scene.
Any value available at the Velocity or Direction data stream may replace
the relevant value of the operator, multiply the relevant value or add
to the relevant value.
Replace - Choosing this option completely replaces the velocity
(and/or direction when that option is chosen) for the particles.
Multiply - Choosing this option takes the existing velocity data,
and multiplies it by the new speed value. So if your particles original
velocity was set to 2.0, and the Velocity operator's Speed setting was
5.0, the resulting Velocity would be 10.0.
Added - Choosing this option takes the existing velocity data,
and adds it to the new speed value. So if your particles original velocity
was set to 2.0, and the Velocity operator's Speed setting was 5.0, the
resulting Velocity would be 7.0.
Per Second checkbox - This checkbox is used to accelerate the
particles to the velocity given when Added or Multiply is active. Within
one second (frame value depends on set frame rate inside of 3ds Max),
the particle is accelerated to the value set.