Locators
Immediately below the Emitter Type selector are
two read-out windows which will show the location of a point emitter on
the canvas. If you are using a rectangle emitter, they will be blank. The
first read-out shows the location on the X-axis, measured in pixels, from
left to right of the frame. The second window is the location on the
Y-axis, measured in pixels, from top to bottom.
Tween Strength
The Tween Strength slider controls
the smoothness of the transitions between each keyframe. With Tween
Strength at 0, the emitter will follow a straight line from one keyframe
to the next. With Tween Strength at 1.00, the program will create a
gradual curve which intersects each of the keyframe points you have set.
This provides much smoother motion, and avoids sudden and obvious changes
in direction.
Relationship to Origin Point
The final attribute for the position of the
particles controls how they relate to the emitter after they are
emitted.
Free From Origin means that
once the particle is emitted, it will follow its set trajectory until the
end of its lifetime, regardless of how the location of the emitter changes
afterward.
Stuck To
Origin means that their relationship to the origin point remains
constant, so that if the emitter moves, the particles will follow it. If
the emitter spins, the particles will spin around the center point of the
emitter.
To make our fire move smoothly, we will increase the Tween Strength to
1.00. Set the particles to Free from Origin, so our fire will move freely
once it is emitted. Make sure Position controls now match this
picture:
Particle Creation
Here we can set how many particles we are
dealing with and what direction they will travel, among other things.
First off, we set whether there are any particles being created at
all.
On/Off Switch
A very basic control, this one! When the
emitter is On, particles will be
generated. When it is Off, no
particles will be emitted. Turning off the emitter has no effect on the
particles which are already in existence.
We want our fire to burn continuously, so leave the switch ON through
the entire effect.
Particle: Max
Controls the maximum number of particles that
can be in existence at any given time. If the Particle:
Max is 500, then once 500 particles are created, no more
particles can be emitted until some of the existing particles reach the
end of their lifetime and disappear.
We won’t be using huge amounts of particles, so you can leave the Max
set to 500.
Particle: Rate
Controls how many new particles are created
each frame.
For this effect, we will only need a Particle Rate of 4.
Particle: Lifetime
Controls how long (in frames) the particle will
last before it disappears. This also has a big impact on many of the other
settings, which I will go into below.
In my NTSC project, I used a Particle Lifetime of 33 frames. If you
are on PAL, you may need to take the difference in frame rate into account
and reduce the lifetime a bit. Try 27 frames.
Reference Point
Next in the Particle Creation controls we have
a menu where we can select the reference point for the angle of our
particle emission.
Relative to Canvas means that
'up' is the top edge of the canvas.
Relative to Animation means
that as the emitter moves around the screen, the direction that the
particles register as 'up' will relate to the direction in which the
emitter is moving.
So if you animate your emitter moving from the
top left to the bottom right of the screen, with Relative to Animation
selected, and the emitter rotation is set to zero, then the particles will
emit at an angle toward the top left corner.
Our fire emitter won’t really move around the screen, so Relative to
Canvas will suit our needs just fine.
