Exercise 19: Variations of one effect

Purpose. To turn one finished explosion into a second one that differs in colour, motion and timing, without rebuilding anything by hand.

A game seldom needs one explosion. It needs a fire version and an ice version, a small one and a large one, a quick one and a slow one. Each could be built again from the first step. It is quicker to duplicate the finished effect and change the duplicate with tools that act on many rows, or many emitters, at once.

Before starting

• The Explosion folder is in the workspace.
• Duplicate it in the Explorer with Ctrl+D, name the duplicate Explosion2, and move it a few studs aside. Everything below is done to Explosion2.

Procedure

Size and Time, from Exercise 10, are two of these tools. This exercise uses the other four.

Step	Control	Action	Result
1	Explosion2	Select	The HUD shows its emitters.
2	≡ ▸ Tools ▸ Hue	Press	A panel titled HueChanger opens, with three upright sliders marked H, S and V.
3	HueChanger ▸ H	Drag it a little, press Emit on the HUD to look, and repeat until the smoke and the flash are blue	Every colour graph in every emitter of the folder shifts together. The flipbook picture keeps its own colours.
4	HueChanger ▸ Apply, then HUD ▸ Emit	Press each	The colours are kept. The explosion plays with blue smoke and a blue flash.
5	The growing ball inside Explosion2	Select	The Properties panel shows it alone.
6	≡ ▸ Tools ▸ Randomize	Press	A panel titled Randomize opens. It lists the emitter’s rows by section, each with a box.
7	Randomize ▸ the box beside Motion	Click	Every row in Motion is ticked.
8	Randomize ▸ Roll, then HUD ▸ Emit	Press each, several times	Each Roll gives the ball new motion values. Each Emit shows them.
9	Randomize ▸ Apply	Press	The last roll is kept. The panel closes.
10	≡ ▸ Tools ▸ PropertyTools	Press	A panel opens with two tabs, Clipboard and Shifter.
11	Clipboard tab ▸ the name Motion in the list	Click	Every row in Motion is ticked and the category opens.
12	Clipboard tab ▸ Copy	Press, with the growing ball still selected	The ball’s Motion values are held.
13	The flipbook flame inside Explosion2	Select, then press Paste	The flame now moves as the ball does.
14	Explosion2	Select. Open the Shifter tab. Tick EmitDelay.	One row is ticked.
15	Shifter tab ▸ the value box, then +	Enter 0.1, then press +	Every emitter in the folder fires a tenth of a second later than before.
16	HUD ▸ Emit button	Press	The second explosion plays: bluer, with new motion, a beat behind the first.

NOTE

Hue, Randomize, Size and Time show their result on the emitters before anything is kept. Apply keeps it. Reset, or Cancel in Randomize, puts the old values back.

CAUTION

Press Apply in the Hue panel before closing it. A change that has not been applied is thrown away when the panel leaves the screen.

NOTE

Hue turns the colour graphs of an emitter and the states of a Blender. It does not turn the colours of a picture. To tint a flipbook, use the Color row of its layer, under Decals.

CAUTION

The Clipboard pastes only the rows that are ticked at the moment Paste is pressed. With nothing ticked, nothing is pasted.

What the steps did

Tool	What it changes	On what
Hue	Every colour graph and every Blender state: turned round the colour wheel (H), made more or less vivid (S), made lighter or darker (V). Not decal layers, and not the pictures themselves.	Everything selected, with the emitters nested inside.
Randomize	The ticked rows, each given a new value at random within sensible limits.	Everything selected. Emitters of the same kind all receive the same roll.
Clipboard	The ticked rows, set to the values copied from another emitter.	Everything selected that has a row of that name.
Shifter	The ticked rows, each multiplied, divided, raised or lowered by the number in the box.	Everything selected that has a row of that name.
Size	Everything measured in studs.	Everything selected.
Time	Everything measured in seconds.	Everything selected.

Each Apply, Paste and Shifter operation is one step in Studio’s undo history.

The four Shifter buttons are marked x, /, + and -. On a row with two numbers, both are changed. On a graph, every keypoint is changed.

The Clipboard carries values between emitters of different kinds where the row has the same name and the same form. A value that does not fit the row it is pasted on is left out without a message.

If the result differs

Symptom	Cause	Action
The Hue sliders change nothing	Nothing with a colour is selected, or the colours are white, grey or black, which have no hue to turn.	Select Explosion2. Use S and V on greys.
Paste does nothing	No row is ticked, or nothing has been copied.	Tick the rows and press Paste again.
The Randomize panel reads No transformed items selected	The selection holds no emitter.	Select an emitter.
Randomize gave two emitters the same values	They are of the same kind and were selected together.	Select and roll them one at a time.
The Hue and PropertyTools panels fold away under the HUD	Nothing the plugin can edit is selected.	Select an emitter. The panels return.

Variations

Change	Result
Randomize ▸ the palette list on a colour row, set to Cool	Rolls keep to blues and greens.
Randomize ▸ Randomize Keypoint/ColorSequence Count on	Graphs and gradients are rolled with several points, not two.
Shifter ▸ tick Rate, enter 0.5, press x	Every stream in the folder makes half as many particles: a cheaper version.
Clipboard ▸ tick OnHit under Events, Copy from one emitter, Paste on others	The whole event, with its picked emitter, is carried over.
V dragged down, Apply	A darker version for a night scene.

Log

New in this exercise	Hue. Randomize. Clipboard. Shifter.
Done before	A Folder selected as one (Exercises 10 and 17). The Tools menu (Exercises 10 and 17). Apply and Reset on a tool (Exercise 10). The Emit button.
Carried forward	Keep both explosions.