Exercise 20: Keep it cheap

Purpose. To find the costly part of an effect and make it cheaper while it still looks the same.

An effect that looks right in an empty scene may be too heavy when twenty of them go off in a fight. The cost is not a matter of taste, and it is not spread evenly. One layer is often responsible for most of it. The plugin shows an estimate of the cost as you work, so the heavy layer can be found and trimmed.

Before starting

• The Explosion folder is in the workspace.
• The flipbook flame inside it is selected, and its Enabled is off.

Procedure

Steps 3 and 4 repeat earlier exercises.

Step	Control	Action	Result
1	≡ ▸ Tools ▸ Opt. Indicator	Press	A label appears at the bottom left of the viewport, beside the particle counter. It reads Optimization: and a percentage.
2	Each emitter in Explosion, one at a time	Select, and read the label	Each layer shows its own figure. Green is light, yellow is moderate, red is heavy. Note which is highest.
3	The flipbook flame ▸ Emission ▸ Rate, Lifetime	Enter 40 and 2	No change yet.
4	Emission ▸ Enabled	Switch on	The flame streams. The figure on the label rises. The counter at the bottom left climbs to about 80 particles.
5	Properties ▸ Advanced	Expand	The Advanced rows show.
6	Advanced ▸ Pool	Switch on	The figure falls. The flame looks the same.
7	Advanced ▸ Anim. Steps	Enter 300	The figure rises. The flame looks no different.
8	Advanced ▸ Anim. Steps	Enter 10	The figure returns to what it read at 100. It does not go lower for fewer steps. Each flame now moves in visible jumps. This is too low.
9	Advanced ▸ Anim. Steps	Enter 100	The motion is smooth again. This was the starting value, and the figure does not change.
10	Emission ▸ Rate	Enter 20	Half as many flames, and the figure falls. Judge by eye whether the stream is still thick enough.
11	Emission ▸ Enabled	Switch off	The label reads the cost of one burst again.

NOTE

The figure is an estimate worked out from the settings. It is not a measurement of the frame rate. Use it to compare two versions of an effect, and to find the layer that matters.

NOTE

An emitter that would do nothing costs nothing. With Enabled off, Emit 0 and Duration 0, the label reads --.

What the steps did

The Optimization indicator gives a figure from 0 to 100 for whatever is selected. It changes as you type, so the effect of every edit on the cost is seen at once.

The particle counter reads the number of particles alive at that moment. For a stream, that number settles at Rate multiplied by Lifetime: 40 a second, each lasting 2 seconds, gives 80.

Pool changes how particles are made. Off, each particle is a fresh duplicate, removed when it ends. On, a finished particle is hidden and used again for the next one. For a stream with a high Rate this is cheaper. For a single burst it makes little difference.

Anim. Steps is how many times a particle’s graphs and motion are worked out over its life. The number of updates each second is Anim. Steps divided by Lifetime. At 100 steps, a particle that lives 1 second is updated on every frame. A particle that lives 5 seconds is updated 20 times a second, which shows as stepping. Raise the steps for long-lived particles, and lower them for short-lived ones.

What raises the figure:

Cause	To lower it
More particles alive at once	Lower Rate, Emit count or Lifetime. A shorter Linger.
A stream with Pool off	Switch Pool on.
Anim. Steps above 100, more so with Drag, or with Dir. Mode Local	Bring Anim. Steps back toward 100. Below 100 the figure does not fall further, though less work is done.
A flipbook, more so with many frames	A shorter flipbook, or one picture.
Particles that are partly transparent	Nothing, if the look needs it. Fewer of them.
Shadows cast by the particle or by a nested light	Switch shadows off on the template.
Nested emitters	Their cost is multiplied by the number of parent particles. Lower the parent’s count first.
Heavy kinds: Models with many parts, Lights, long Trails, bolts with many segments and forks, bursts with many chunks, ropes with many segments	Fewer parts, segments, forks or chunks.

If the result differs

Symptom	Cause	Action
No label at the bottom left	The indicator is off. It is off at the start of every session.	Repeat step 1.
The label reads --	The selected emitters would do nothing as they stand.	Switch Enabled on, or enter an Emit count.
New particles stop appearing, and Output mentions the particle cap	The number alive has reached the Particle Cap.	Lower Rate or Lifetime, or raise Particle Cap in Settings.
Changing Pool or Anim. Steps does nothing to particles in flight	They keep the settings they were made with.	Wait one Lifetime.

Variations

Change	Result
Select the whole Explosion folder	The figure for the entire effect.
Shifter ▸ tick Rate, enter 0.5, press x	Every stream in the folder makes half as many particles, in one move.
≡ ▸ Settings ▸ Particle Cap 300	A hard ceiling while you work. Layers that hit it show which are greedy.

Log

New in this exercise	The Optimization indicator. The particle counter. Pool. Anim. Steps.
Done before	Rate and Lifetime (Exercise 2). Enabled (Exercise 1). Expanding a section (Exercises 5 and 7). The Tools menu (Exercises 10, 17 and 19). The Particle Cap (Exercise 2).
Carried forward	Nothing. This is the last exercise.