Lightning

A Lightning emitter makes bolts: jagged lines of thin segments from a start point to an end point. A bolt reshapes itself many times a second. It can branch into forks, be drawn from one end to the other, taper, and leave a disk where it lands.

Exercise 12 makes a Lightning emitter for the first time.

What it makes possible:

An arc between two props. Mode Animate, Loop on, Target Mode Point, Target set to the other prop. One bolt stays and tracks both ends.
A strike from the sky. An emitter high up, Direction Bottom, Growth Speed 300, 800, a Taper graph from 1 to 0.2, Lifetime 0.3, Fork Chance 0.6, Fork Depth 2. Each bolt races down at a speed of its own.
A scorch that drags across the floor. Target Mode Seek, Retarget on, Retarget Speed 40, Impact Disk on with a scorch image, On Hit firing sparks with Mode AtPosition.
A crown of bolts. Rotation Y 0, 360 with its Even dot on, Dir. Mode Local, Direction Front, Emit 8.
A ball that bristles with bolts. Use shape on, Shape Sphere, Hollow 1, Bolt Direction Radial, Emit 12, a short Length.
A slow tendril of plasma. Shape Mode Scroll, Waves 2, Scroll Speed 0.5, Sag 0.2, Sag Shape 0.5, a Gradient from white to blue, Material Neon.
A bolt that lights the room. A Light emitter with Emit 1 inside the Lightning RenderTemplate.

At a glance


Made from	A Part or a MeshPart, with Transform as Lightning
One particle is	One bolt with its forks
Emit count starts at	1
Modes	Emit and Animate
Sections	Emission, Appearance, Spawn, Motion, Bolt, Impact, Events, Advanced
Not present	Link. The bolt follows the emitter Part itself.

An Emit count of 3 means three bolts, not three segments. A bolt counts as one particle toward the particle counter and the Particle Cap, however many segments it has.

A bolt is a temporary group of parts. It is not solid. Characters walk through it, and it pushes nothing.

Spawn, Motion, Impact, Events and Advanced start collapsed.

Where a bolt starts and ends

A bolt starts at the emitter Part, moved by the rows of the Spawn section. Its end is chosen by Bolt ▸ Target Mode.

The bolt reads the emitter Part’s own position and rotation at every reshape. Move the Part, or weld it to something that moves, and the start of the bolt goes with it.

Case	The bolt starts
The emitter stands by itself	At the emitter Part, and follows it.
The emitter is nested in another emitter	At the parent particle, and rides it.
The emitter is fired by another emitter’s event	At the spot of the event, and stays there.
The emitter Part is removed while a bolt is alive	At the last place the Part had.

Transform as Lightning

Select a Part. Press ▾ beside Transform, then Transform as Lightning.

Any Part or MeshPart that is not yet an emitter can be used. It may hold a SpecialMesh, Decals, Textures or a SurfaceAppearance.

Thing	After the transform
The Part	It turns fully transparent. It marks where bolts start.
`RenderTemplate`	A hidden copy of the Part. Every segment of every bolt is a duplicate of it.
A SpecialMesh, Decal, Texture or SurfaceAppearance in the Part	It is kept in the `RenderTemplate`, so every segment shows it.
A SpecialMesh, Decal or Texture on the Part itself	It is removed from the Part.
An Attachment or an emitter already transformed, inside the Part	It is kept in the `RenderTemplate`.
Any other child of the Part	It is not kept in the `RenderTemplate`.
Thickness row	It takes the smaller of the Part’s X and Y size, and at least 0.05 studs.
Color and Transparency rows	They take the Part’s colour and transparency.
Material	It stays on the `RenderTemplate`. The Material row edits it.
HUD ▸ Emit box	It reads 1.

The Part’s Size is not kept as a row. The length of a segment comes from the bolt. Its width comes from Thickness.

Because the Emit count starts at 1, the Emit button makes one bolt straight after the transform.

The Explorer shows five things inside the emitter: PartIcleProperties, RenderTemplate, EmitParent, ShapePart and Target. The last three hold the Emit Into, Shape Part and Target rows. See EmitParent, Link, AccelTarget, ShapePart.

A stock ParticleEmitter in the Part is not carried over. Put it into the RenderTemplate after the transform.

To change the look later, edit the RenderTemplate in Studio, or use the Appearance rows.

Emission

Row	Kind	Starts at	Unit	What it does
Mode	List	`Emit`		`Emit` makes a new bolt at every emit. `Animate` plays one bolt in place.
Loop	Switch	Off		Animate mode only. Repeats the cycle until switched off.
Enabled	Switch	Off		Emit mode only. Makes bolts at the Rate until switched off.
Rate	Number	10	Bolts per second	How many bolts are made each second while Enabled is on, or during a Duration. Hidden in Animate mode.
Lifetime	Two numbers	1	Seconds	How long one bolt lasts. Each bolt picks a value between the two.
Linger	Number	0	Seconds	After its Lifetime the whole bolt stays frozen in its last frame for this long.
Timescale	Graph	1		The speed of the bolt’s own clock.

The Emit, Delay and Duration boxes on the HUD fire a Lightning emitter as they fire any other. After the Delay, the Emit count of bolts is made at once. With a Duration above 0, the emitter then runs at its Rate for that long. The rows are described in full on Emission and the HUD.

Emit mode and Animate mode

	Emit mode	Animate mode
What exists	A new bolt at every emit. Several can be alive at once.	One bolt for the emitter.
Fired again while a bolt is alive	Another bolt is added.	The press is ignored until the bolt ends.
End of a cycle without Loop	The bolt is removed after its Linger.	The bolt holds its last frame for the Linger, then is removed.
Loop on	Not used.	The same bolt lives on from cycle to cycle.
Emit count	Used.	Not used.
Even dots	Used.	Not used. The axis picks at random.
Pool	Used if on.	Not used.

With Loop on, four things happen at the start of each cycle:

Every row is read again, and every two-number row picks a new value.
Growth Speed starts from the beginning.
A Seek bolt drops its strike point and searches again.
The bolt reshapes once, and the Impact disk is made again.

An edit made while a loop runs shows at the start of the next cycle.

Timescale on a bolt

Timescale	What you see
Above or below `1`	Reshapes, the Scroll wave, Growth Speed and the Motion rows all run faster or slower.
`0`	The bolt freezes. It does not reshape and does not grow.
Below `0`	Growth Speed runs backwards and the drawn part of the bolt shortens. The Motion rows unwind. The bolt keeps flickering.

Appearance

Row	Kind	Starts at	Unit	What it does
Material	List	The Part’s material		The material of every segment. A change shows from the next bolt.
Color	Colour	The Part’s colour		The colour of the bolt over its life.
Gradient	Colour	White		The colour along the bolt, from the source to the tip. Plain white switches it off.
Brightness	Graph	1		Multiplies the colour, over the bolt’s life. It is not a light.
Transparency	Graph	The Part’s transparency	0 to 1	Fades the bolt over its life.
Thickness	Graph	The smaller of the Part’s X and Y size	Studs	The width of the bolt over its life.
Taper	Graph	1		The width along the bolt, as a multiple of Thickness.

Material writes straight to the RenderTemplate. The row shows the material the RenderTemplate has now. Neon is what makes a bolt glow.

Color and Gradient are both drawn as gradients, and they read differently. On Color, the left end is the birth of the bolt and the right end is the end of its life. On Gradient, the left end is the source of the bolt and the right end is its tip. The two are multiplied together. A fork takes the Gradient colour of the place where it leaves the bolt.

Color also tints a Decal or a Texture on the segments, and Transparency fades it.

Brightness multiplies each part of the colour, and no part can go above full. On a white bolt a value above 1 changes nothing. A value below 1 darkens the bolt. For a bolt that lights the scene, see Nesting.

Thickness is measured in studs. A segment is as wide as it is tall. A bolt is never thinner than 0.05 studs.

Taper is a graph along the bolt, not over its life. The left end of the graph is the source and the right end is the tip.

Taper graph	Result
Flat at 1	No taper. The row starts this way.
From 1 to 0	The bolt thins to a point at its tip.
From 0 to 1 and back to 0	The bolt is sharp at both ends.

A value below 0 counts as 0. The limit of 0.05 studs still applies. A fork starts at the width of its branch point and ends at the tip value.

Forks are thinner than the main bolt. No row sets this.

Spawn

These rows move and turn the start of the bolt. Position, Rotation, the Even dots, the Cycle rows, Rot Order and axis linking work as on a Part emitter. They are described on Spawn.

Row	Kind	Starts at	Unit	What it does
Dir. Mode	List	`RigidLocal`		How Bolt ▸ Direction is read in `Directional` mode.
Rot Order	List	`Global`		The order in which the three Rotation angles are combined.
Rotation	Two numbers for each of X, Y, Z	0	Degrees	A rotation picked for each bolt.
Rot. Cycle	Two numbers	0	Bolts	The length of one even sweep of Rotation. Shown while a Rotation Even dot is on.
Pos. Mode	List	`Local`		The axes the Position offset is measured along.
Position	Two numbers for each of X, Y, Z	0	Studs	Moves the start of each bolt.
Pos. Cycle	Two numbers	0	Bolts	The length of one even sweep of Position. Shown while a Position Even dot is on.
Use shape	Switch	Off		Scatters the starts of bolts inside a shape. Shows the five rows below.
Shape	List	`Box`		The shape: `Box`, `Sphere`, `Cylinder` or `Disc`. It takes its measurements from the shape part’s Size.
Bolt Direction	List	`Emitter`		Whether the shape also sets the direction of the bolt.
Radial Dir	List	`Outward`		With Bolt Direction `Radial`: `Outward`, `Inward` or `InAndOut`.
Hollow	Number	0	0 to 1	At 0 the whole shape is used. At 1 only its outer surface or rim is used.
Shape Part	Instance, picked with `*`	The emitter itself		Another part whose Size and position give the shape.

Dir. Mode

Option	Bolt ▸ Direction runs along
`RigidLocal`	The emitter’s own axes. The Rotation row does not turn the bolt.
`Local`	The emitter’s axes, turned by the Rotation picked for that bolt. This is the mode for crowns and fans.
`Global`	The axes of the world. Rotating the emitter does not turn the bolt.

Rotation and Position

Rotation always turns the axes of a Local Position offset and of a Local Displacement. It turns the direction of the bolt only when Dir. Mode is Local.

Pos. Mode Local measures the offset along the emitter’s axes, after the Rotation. Global measures it along the axes of the world.

Position is applied again at every reshape, against the place the emitter has at that moment. A pattern of bolts therefore rides a moving emitter.

In a burst, each bolt takes its own step of an Even axis. Rotation Y 0, 360 with its Even dot on and Emit 8 gives eight bolts at equal angles.

Use shape

Bolt Direction	Result
`Emitter`	The shape only scatters where bolts start. Each bolt still goes along Direction, tilted by SpreadAngle.
`Radial`	Each bolt goes along the outward direction of the shape at its start point.

Radial applies in Target Mode Directional only.
Radial Dir matters only with Bolt Direction Radial. Inward reverses the direction. InAndOut reverses it for a random half of the bolts. The row shows in either case.
Hollow has no effect on a Box.
Shape Part accepts a Part or a MeshPart. The shape then takes that part’s Size and follows its position.
There is no Look at initially row on a Lightning emitter.

Motion

These rows move the start of the bolt over its life. They do not throw the bolt like a projectile. The graphs and boxes of Speed, Acceleration, Drag, Displacement and Turbulence work as on a Part emitter. They are described on Motion.

Row	Kind	Starts at	Unit	What it does
Speed	Graph	0	Studs per second	Slides the start along the bolt’s own direction.
Acceleration	Three numbers, `x, y, z`	`0, 0, 0`	Studs per second per second	A drift of the start that grows steadily, along the axes of the world.
Drag	Number	0		Slows the Speed as the bolt ages.
Displacement Mode	List	`Global`		The axes used by Displacement, Turbulence and Bolt ▸ Sag.
Displacement	Graph for each of X, Y, Z	0	Studs	An offset of the start over the bolt’s life.
Turbulence	Graph	0	Studs	A smooth random wander of the start. The value is how far it wanders.
Turb. Frequency	Number	1		How fast the wander changes.

The bolt’s own direction depends on Target Mode. In Directional it is the launch direction. In Point and Seek it points toward the end of the bolt.

Displacement Mode	Axes
`Global`	The axes of the world.
`Local`	The emitter’s axes, turned by the Rotation picked for that bolt.
`RigidLocal`	The emitter’s axes.

What moves with the start depends on Target Mode:

Target Mode	Result of moving the start
`Directional`	The end is a set Length from the start, so the whole bolt travels.
`Point`	The end stays on the Target. The bolt stretches or shortens.
`Seek`	The strike point stays where it was found, unless Retarget is on.

Bolt

A two-number row gives each bolt a value of its own. The bolt picks it when it is made, and again at each cycle of an Animate loop.

Row	Kind	Starts at	Unit	What it does
Target Mode	List	`Directional`		How the end of the bolt is chosen: `Directional`, `Point` or `Seek`.
Target	Instance, picked with `*`	None		The end of the bolt in `Point` mode.
Seek Radius	Two numbers	30	Studs	How far a `Seek` bolt looks for a surface. A value below 1 counts as 1.
Retarget	Switch	Off		Off, a `Seek` bolt keeps one strike point. On, it searches again at every reshape.
Seek Bias	Number	0	0 to 1	At 0 every surface found is equally likely. At 1 the nearest one found almost always wins.
Retarget Speed	Number	0	Studs per second	At 0 the strike point jumps. Above 0 it slides to each new point at this speed.
Direction	List	`Top`		The face of the emitter the bolt leaves from. `Top` is the Part’s up axis.
SpreadAngle	Two numbers, `x, y`	`0, 0`	Degrees	Tilts each bolt by a random angle, up to x on one axis and up to y on the other.
Length	Two numbers	20	Studs	The straight distance from the start to the end. A value below 0.1 counts as 0.1.
Growth Speed	Two numbers	0	Studs per second	At 0 the whole bolt appears at once. At any other value the bolt is drawn along its length at this speed.
Shape Mode	List	`Jitter`		How the bolt moves: `Jitter`, `Scroll` or `JitterScroll`.
Segments	Two numbers	12	Count	The straight pieces in the main bolt, from 2 to 64.
Amplitude	Two numbers	0.15	Share of the bolt’s length	How far the bolt strays from a straight line.
Amp. Decay	Two numbers	0.5	0 to 1	How much smaller the fine zigzags are than the large ones.
Jitter Rate	Two numbers	15	Reshapes per second	How often the bolt reshapes. At 0 the shape is made once and kept.
Scroll Speed	Two numbers	1	Waves per second	How fast the wave travels along the bolt. A negative number reverses the travel.
Waves	Two numbers	3	Count	How many waves fit along the bolt. A value below 0.25 counts as 0.25.
Sag	Two numbers	0	Share of the bolt’s length	The droop of the whole bolt at its middle. A negative number arches it upward.
Sag Shape	Two numbers	1		The outline of the droop.
Fork Chance	Two numbers	0	0 to 1	The chance that each possible fork shows at each reshape. At 0 there are no forks.
Fork Depth	Two numbers	0	0 to 2	0 gives no forks. 1 gives forks off the main bolt. 2 adds forks off those forks.
Fork Length	Two numbers	0.4	Share of the bolt’s length	The length of a fork.

A two-number row also takes one number, which serves for both. A row keeps the number as typed. The limits in the table are applied when a bolt is made.

The rows shown depend on Target Mode and Shape Mode:

Rows	Shown when
Target	Target Mode is `Point`
Seek Radius, Retarget, Seek Bias, Retarget Speed	Target Mode is `Seek`
Direction, SpreadAngle, Length	Target Mode is `Directional`
Growth Speed	Target Mode is `Directional` or `Seek`
Scroll Speed, Waves	Shape Mode is `Scroll` or `JitterScroll`
Every other row	Always

When the selected Lightning emitters differ in mode, every row shows.

Target Mode

Directional. The bolt leaves the start along Direction, tilted by SpreadAngle. It ends Length studs away. Spawn ▸ Dir. Mode decides which axes Direction is read on. With Use shape on and Bolt Direction Radial, the direction comes from the shape.

Point. The bolt runs from the start to the Target. The Target row accepts a Part, a MeshPart, an Attachment, a Model, a Bone or the Camera. The picking box has a Clear button.

The end of the bolt is the centre of a Part, the place of an Attachment, or the pivot of a Model. On a Bone it is the animated place.
The Target is read again at every reshape. A moving Target is followed, in steps at the Jitter Rate.
If the Target is removed while a bolt is alive, the end stays at its last place.

Seek. Each bolt looks around its start for surfaces within Seek Radius, and strikes one of them.

Seek finds surfaces: floors, walls, and any part with collisions on. It does not home in on players, enemies or a chosen object.
Seek samples the surroundings. Large, near surfaces are found far more often than small or distant ones.
To prefer near surfaces, raise Seek Bias. To strike one chosen thing, use Point.
With no surface found, the bolt arcs into open air. It goes in a random direction, for half the Seek Radius.

What counts as a surface:

Counts	Does not count
A part with CanCollide on	A part with CanCollide off
Terrain	Water
	The emitter, its `RenderTemplate`, and the plugin’s own particles
	The Emit Into instance and everything inside it
	Whatever the Hit Filter leaves out

Retarget and Retarget Speed decide how the strike point behaves over the bolt’s life:

Retarget	Retarget Speed	The strike point
Off	Any	Is chosen once. The bolt still reshapes around it.
On	0	Is searched for again at every reshape. It flickers between surfaces at the Jitter Rate.
On	Above 0	Slides to each new point at that speed. The next search waits until the slide has arrived.

With a Retarget Speed above 0, the bolt drags its end across surfaces from one point to the next. The first strike of a bolt always appears in place, with no slide.

Growth Speed

Growth Speed draws the bolt along its length, at a speed in studs per second.

Growth Speed	Result
`0`	The whole bolt appears at once.
Above 0	The bolt is drawn from the source toward the tip.
Below 0	The far end appears first, and the bolt fills in back toward the source.
Two numbers, such as `300, 800`	Each bolt picks a speed of its own.
Two numbers on either side of 0, such as `-200, 200`	Some bolts are drawn from the source and some from the far end.

The distance is measured along the zigzag, which is a little longer than the straight Length.
With Length 20 and Growth Speed 100, the bolt is fully drawn after a little over 0.2 seconds.
With Length 20, Growth Speed 20 and Lifetime 1, the bolt ends before it is fully drawn.
A fork appears when the growth reaches its branch point. It then grows at the same speed.
Below 0, the far end is the farthest tip of the bolt, forks included.
The growth follows the bolt’s own clock. A Timescale of 2 doubles it. A Timescale below 0 runs it backwards.
A bolt does not shrink back by itself at the end of its life.

Shape Mode

Shape Mode	What you see	What the Jitter Rate does
`Jitter`	A random zigzag that snaps to a new random zigzag at each reshape.	Reshapes the whole bolt.
`Scroll`	A smooth wave that travels along the bolt every frame. The two ends stay fixed.	Makes new forks only, and reads the end points again.
`JitterScroll`	A random zigzag with the travelling wave laid on top.	Reshapes the zigzag and the forks.

In the two Scroll modes:

The size of the wave is Amplitude times the length of the bolt.
A second, finer wave rides on the first. Amp. Decay sets its size.
Waves sets how many waves fit along the bolt. Scroll Speed sets how fast they travel.
A negative Amplitude mirrors the wave to the other side.
Forks stay attached to the moving bolt, and each waves by itself.

Amplitude, Amp. Decay and Sag

Amplitude is a share of the bolt’s length. At 0.15 on a bolt of 20 studs, the middle strays up to 3 studs sideways. At 0 the bolt is straight.

Amp. Decay compares each finer level of zigzag with the level above it.

Amp. Decay	Result
`0.5`	Each finer level is half as large as the one before.
Near 1	The bolt is jagged at every scale.
Near 0	One large bend, and smooth otherwise.

Sag is a share of the bolt’s length. At 0.2 on a bolt of 20 studs, the middle hangs 4 studs lower. Down is set by Motion ▸ Displacement Mode. With Global it is the world’s down. Forks do not sag.

Sag Shape sets the outline of the droop:

Sag Shape	Outline
`1`	A parabola.
Above 1	More pointed.
`0.5`	A true arc of a circle. With a large Sag it bulges past a half circle into a horseshoe.
`0`	A square trough.
Between these	A blend of the two nearest.

Jitter Rate and the reshape

A reshape is the only moment a bolt reads the world again. At a reshape the bolt reads the place of the emitter and of the Target. It applies the Spawn and Motion offsets. A Seek bolt with Retarget on searches again.

The plugin builds the zigzag again from the rows at each reshape. With Jitter Rate at 15 that is 15 times a second.

An Animate bolt with Loop on reshapes once at the start of each cycle, even at Jitter Rate 0.
A low Jitter Rate makes a bolt on a moving object lag behind it in steps. Keep the Jitter Rate at or above the number of steps a second the tracking needs.
Forks are decided again at each reshape, so they come and go at the Jitter Rate. At Jitter Rate 0 the forks made with the bolt stay.
In a very heavy scene, a bolt may reshape one frame late.

Forks and the part limit

A bolt has at most 64 parts. The main bolt and its forks share them. A bolt has at most 6 forks.

Fork Depth	Forks at one time
`0`	None.
`1`	At most 3, all off the main bolt.
`2`	At most 6. Up to three leave the main bolt, and up to three leave a fork.

A value of 3 or more behaves as 2. A value with a fraction is rounded.
A fork off a fork shows only when a fork off the main bolt showed in the same reshape.
Each fork has about half as many pieces as the main bolt. With Segments 12, a fork has 6 pieces, and 6 forks bring the bolt to 48 parts.
Segments 64 leaves no room for forks.
Fork Length is applied once for each level. At 0.4 on a bolt of 20 studs, forks are 8 studs long. Forks off those forks are 3.2 studs long.
A fork is never shorter than 1 stud. Its zigzag shrinks by the same share as its length.
Each fork leaves at a random point of the main bolt, or at the middle of the fork it grows from. It leaves at a moderate angle. No row sets the angle.
Forks do not strike anything. They never fire On Hit.

Impact

The Impact section adds a thin, flat disk at the place the bolt lands.

Row	Kind	Starts at	Unit	What it does
Impact Disk	Switch	Off		Adds the disk. The rows below show only while it is on.
Disk Mode	List	`Follow`		`Follow` ties the disk to the bolt’s Thickness and Transparency. `Manual` uses the disk’s own graphs.
Disk Size	Graph	2	Studs	The width of the disk across, over the bolt’s life. Never smaller than 0.05 studs.
Disk Transp.	Graph	0	0 to 1	The transparency of the disk. `Manual` only. The row is hidden in `Follow`.
Disk Bright.	Graph	1		Multiplies the disk’s colour, as Brightness does. `Manual` only. The row is hidden in `Follow`.
Disk Texture	Text	Empty		An image shown on the outward face of the disk.
Disk Offset	Number	0.05	Studs	How far the disk is lifted off the surface, so the two do not flicker.

Where the disk shows

The disk exists only while the bolt lands on a surface. A bolt that ends in the air shows no disk.

Target Mode	The disk sits at
`Seek`	The strike point.
`Point` and `Directional`	The first surface on the straight line from the start of the bolt to its end.

The surface rules are those of Seek, in the table under Target Mode.
A Point Target with CanCollide off gives no disk. Neither does an Attachment in open air.
The disk does not shorten the bolt. In Directional mode a wall halfway along gets the disk, and the bolt carries on through the wall.
The disk lies flat on the surface.
The disk moves when the bolt reshapes.
The disk is removed with the bolt. In Emit mode that is after the Linger.

How the disk looks

The colour of the disk always follows the tip of the bolt. It is the Color row, times the Brightness, times the right end of the Gradient. There is no separate disk colour.
The material of the disk is the material of the RenderTemplate.
Taper does not change the disk.

In Follow mode, Disk Size is the size at full opacity and at the Thickness the bolt started with. The disk grows and shrinks with Thickness, and shrinks as the bolt fades.

Disk Size	Thickness now, against Thickness at the start	Transparency	Width of the disk
2	The same	0	2 studs
2	The same	0.5	1 stud
2	Half	0	1 stud

Disk Texture

The hint in the empty box reads rbxassetid://... or none. With an image set, only the image shows, and the body of the disk is hidden. Enter none to clear the row.

Events

A Lightning emitter has the four event blocks and a Hit Filter row. Events are described in full on Events.

Event	On a Lightning emitter
On Emit	Present.
On Death	Present.
On Destruction	Present.
On Hit	Present only while Target Mode is `Seek`.

On Hit

On Hit fires when a Seek bolt finds a strike point on a surface.

Case	On Hit fires
Retarget off	Once, when the bolt is made.
Retarget on, Retarget Speed 0	When the bolt is made, and again at each new strike point.
Retarget on, Retarget Speed above 0	When the bolt is made, and each time the slide arrives at a new point.
No surface found	Not at all.

An event script receives the instance that was struck, the position, and the direction the surface faces. See The event script and its payload.

Where On Emit and On Death place a target

With Mode AtPosition, a target fired by On Emit, On Death or On Destruction appears at the start of the bolt. It does not appear at the tip.

To act at the tip, use Seek with On Hit, or use the Impact disk.

In an event script, payload.SetColor and payload.SetTransparency act on every segment of the bolt.

Hit Filter

The Hit Filter row is at the top of the Events section. It belongs to the emitter, not to On Hit. It limits what Seek and the Impact disk count as a surface, and it applies while On Hit is off.

A Lightning emitter as the target of an event

Another emitter’s event can fire a Lightning emitter. Pick it in the event’s Emit row. Its Emit count of 1 means it fires with no more setup.

The start of the bolt is fixed at the spot of the event for the bolt’s whole life. It does not follow anything.
Mode AtPosition uses that spot with the Lightning emitter’s own rotation.
Mode AtCFrame uses that spot, turned the way the event’s particle was turned.
The Position, Rotation and Use shape rows still apply on top.

Advanced

Row	Kind	Starts at	What it does
Anim. Steps	Number	100	How many times the appearance graphs are read over one Lifetime.
Emit Into	Instance, picked with `*`	None	Where the parts of a bolt are placed in the Explorer.
Preload Texture	Switch	Off	Keeps every texture the emitter uses loaded, so the first bolt does not show blank textures.
Pool	Switch	Off	Reuses finished bolts in place of making new ones. For emitters with a high Rate.

Anim. Steps acts on Color, Brightness, Transparency, Thickness and the disk graphs. The shape of the bolt does not use it. The bolt reshapes at its Jitter Rate, on a clock of its own. A value of 0 or less counts as 100.

Emit Into does not change where a bolt appears.

Nesting

Nesting is described in full on Nesting.

What is put where	Result
A transformed emitter inside the Lightning `RenderTemplate`	It fires once for each bolt, at the start of the bolt. It does not fire once for each segment.
A Light emitter inside the Lightning `RenderTemplate`	Every segment of the bolt carries the light, so the whole bolt glows.
A stock ParticleEmitter, Trail or Beam inside the `RenderTemplate`	Every segment has one of its own, because every segment is a duplicate of the `RenderTemplate`.
A Lightning emitter inside the `RenderTemplate` of a Part, Attachment or Model emitter	The bolt starts at the parent particle and rides it.

The nested emitter’s own Emit, Delay and Duration decide what it does for each bolt.
With Mode Animate and Loop on, nested emitters fire again at every cycle.
All the lights on a bolt follow the Light emitter’s graphs and are removed with it.
A stock Trail or Beam in the RenderTemplate runs only with a Duration above 0. See Editing stock ParticleEmitters, Trails and Beams.

With the tools

Tool	Effect on a Lightning emitter
Size	Multiplies the Thickness, Speed, Displacement, Turbulence and Disk Size graphs. Multiplies Acceleration, Length, Position, Seek Radius, Growth Speed, Retarget Speed and Disk Offset.
Time	Multiplies Rate, Drag, Turb. Frequency, Retarget Speed, Jitter Rate, Scroll Speed, Growth Speed and the Speed graph. Divides Lifetime. Multiplies Acceleration by the square of the factor.

Size does not change Amplitude, Sag or Fork Length. They are shares of the bolt’s length, so they follow Length. It does not change Taper, Segments or SpreadAngle.

Time does not change Linger or Anim. Steps. It divides the Delay and Duration on the HUD, as for every emitter.

The tools are described on Size and Time.

Motion Preview does not draw a Lightning emitter.

Limits

A bolt has at most 64 parts and 6 forks. Segments runs from 2 to 64.
A bolt passes through everything. Only Seek and the Impact disk look at the world.
Seek does not aim at characters or chosen objects. It finds surfaces.
Jitter Rate 0 stops the bolt from following anything.
On Emit and On Death place a target at the start of the bolt, not at its tip.
Sag does not show on a bolt that runs along the sag direction. A vertical bolt with Displacement Mode Global is one case.
There is no Link. The bolt follows the emitter Part itself.
An edit acts on bolts made after it. A bolt that is alive keeps the values it picked. An Animate loop takes the edit at its next cycle.
A bolt has no light of its own. Brightness only scales its colour.

What makes a Lightning emitter cost more:

Setting	Why
Segments and forks	More parts are moved at every reshape.
Jitter Rate	More reshapes each second.
Shape Mode `Scroll` or `JitterScroll`	The bolt is redrawn every frame.
Rate times Lifetime	More bolts alive at once.
Retarget in `Seek` mode	A new search at every reshape, for every bolt.
A nested Light	One light for every segment.