Rocks

A Rocks emitter throws bursts of debris. Each chunk is a duplicate of the Part, at a size of its own. The chunks fly out, fall, bounce, slide to rest flat on one face, and can sink into the ground before they vanish.

Exercise 13 makes a Rocks emitter for the first time.

What it makes possible:

• A ground slam. Burst Mode Ring, Direction Top, SpreadAngle 30, Launch Speed 50, 80, Sink Out on. Rubble flies out in a ring, settles, and sinks away.
• Dust under every chunk. On Hit with a dust emitter in its Emit row, Mode AtPosition, Hit Per Chunk on.
• Rubble that matches the floor. Inherit Floor on. Each chunk takes the material and colour of the part it lands on.
• An object that comes back together. Timescale -1. The chunks start at rest and fly back to where they were thrown from.
• Shards that float away. A negative Gravity such as -20, Sink Out off, a Transparency graph from 0 to 1.
• A trail on every chunk. A stock Trail with a Duration above 0, inside the Rocks RenderTemplate.

At a glance

Made from	A Part or a MeshPart, with Transform as Rocks
One particle is	One burst of chunks
Emit count starts at	1
Modes	Emit and Animate
Sections	Emission, Appearance, Spawn, Motion, Events, Advanced
Not present	Link, and a Rotation row. Each chunk starts turned at random.

An Emit count of 2 means two bursts, not two chunks. The number of chunks is its own row. A burst counts as one particle toward the particle counter and the Particle Cap, however many chunks it has.

A burst is a temporary group of parts. The chunks are not solid. Characters walk through them, and they push nothing.

Events and Advanced start collapsed.

Where a burst starts

A burst reads the place of the emitter Part once, at the moment it is fired. The chunks then fly through the world by themselves. Moving the emitter afterwards does not move a burst already in the air.

Case	The burst is thrown from
The emitter stands by itself	The emitter Part, where it is when the burst is fired.
The emitter is nested in another emitter	The parent particle, where it is at that moment.
The emitter is fired by another emitter’s event	The spot of the event.

Transform as Rocks

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

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 bursts are thrown from.
RenderTemplate	A hidden copy of the Part. Every chunk is a duplicate of it.
A SpecialMesh, Decal, Texture or SurfaceAppearance in the Part	It is kept in the RenderTemplate, so every chunk 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.
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.

Because the Emit count starts at 1, the Emit button throws one burst straight after the transform.

The Explorer shows three things inside the emitter: PartIcleProperties, RenderTemplate and EmitParent. EmitParent holds the Emit Into row.

CAUTION

Transform as Rocks switches off CanCollide on the Part itself.

Where the chunk look comes from

The look of a chunk comes from the RenderTemplate, which is the Part that was transformed.

The Part was	Every chunk is
A block	A block.
A MeshPart rock	That mesh.
A Part with a SpecialMesh, Decals, Textures or a SurfaceAppearance	The same, with all of them kept.

• The plugin includes no rock mesh of its own.
• The size of a chunk is the Size of the RenderTemplate, times the chunk’s Chunk Scale. The Part’s Size is not kept as a row.
• To change the look later, edit the RenderTemplate in Studio, or use the Appearance rows.
• With Inherit Floor on, a chunk takes its material and colour from the part it lands on.

Emission

Row	Kind	Starts at	Unit	What it does
Mode	List	Emit		Emit throws a new burst at every emit. Animate plays one burst at a time.
Loop	Switch	Off		Animate mode only. Repeats the cycle until switched off.
Enabled	Switch	Off		Emit mode only. Throws bursts at the Rate until switched off.
Rate	Number	2	Bursts per second	How many bursts are thrown each second while Enabled is on, or during a Duration. Hidden in Animate mode.
Lifetime	Two numbers	3	Seconds	How long one burst lasts. All its chunks share the one Lifetime.
Linger	Number	0	Seconds	After its Lifetime the whole burst stays frozen in its last frame for this long.
Timescale	Graph	1		The speed of the burst’s own clock.

The Emit, Delay and Duration boxes on the HUD fire a Rocks emitter as they fire any other. After the Delay, the Emit count of bursts is thrown at once. Each burst picks its own number of chunks. 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 burst at every emit. Several can be alive at once.	One burst for the emitter.
Fired again while a burst is alive	Another burst is added.	The press is ignored until the burst ends.
End of a cycle without Loop	The burst is removed after its Linger.	The burst holds its last frame for the Linger, then is removed.
Loop on	Not used.	Each cycle throws a new burst from the place the emitter has at that moment.
Emit count	Used.	Not used.
Pool	Used if on.	Not used.

With Loop on, every cycle is a new burst. The chunks are picked afresh, and their paths are worked out again. An edit made while a loop runs shows at the start of the next cycle.

Timescale and exact rewind

Timescale	What you see
Above or below 1	The whole flight plays faster or slower.
0	The chunks hang in the air.
Below 0	The flight plays exactly backwards. The chunks fly back to the point they were thrown from.

A burst rewinds exactly: it is the same flight, played backwards. Timescale -1 starts the chunks at rest and flies them back together.

Sink Out follows the same clock. Timescale 0 pauses the sinking. A Timescale below 0 raises sunken chunks back out of the ground.

Appearance

Row	Kind	Starts at	Unit	What it does
Material	List	The Part’s material		The material of every chunk. A change shows from the next burst.
Color	Colour	The Part’s colour		The colour of all the chunks over the burst’s life.
Brightness	Graph	1		Multiplies the colour, over the burst’s life. It is not a light.
Transparency	Graph	The Part’s transparency	0 to 1	Fades all the chunks over the burst’s life.
Scale	Graph	1		Multiplies the size of every chunk over the burst’s life.

Material writes straight to the RenderTemplate. The row shows the material the RenderTemplate has now.

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

Brightness multiplies each part of the colour, and no part can go above full. On a white chunk a value above 1 changes nothing. A value below 1 darkens the chunk.

Scale acts on top of each chunk’s own Chunk Scale. The graph cannot go below 0, and a value below 0.01 counts as 0.01.

Spawn

Row	Kind	Starts at	Unit	What it does
Burst Mode	List	Directional		The pattern of the throw: Directional or Ring.
Chunks	Two numbers	6, 10	Count	How many chunks are in a burst. Each burst picks a whole number between the two.
Chunk Scale	Two numbers	0.5, 1.5	Multiple of the RenderTemplate Size	The size of each chunk. Each chunk picks one value and is scaled evenly by it.
Pos. Mode	List	Local		The axes the Position offset is measured along: the emitter’s, or the world’s with Global.
Position	Two numbers for each of X, Y, Z	0	Studs	Where each chunk starts, measured from the place the burst is thrown from. Each chunk picks its own offset.

The Position row and its Even dots are described on Spawn. A Rocks emitter has no Rotation row and no Cycle rows.

Burst Mode

Burst Mode	Result
Directional	Every chunk goes along Motion ▸ Direction. Each is tilted at random within the SpreadAngle.
Ring	The chunks are spaced evenly around the Direction axis and fly outward. The first number of SpreadAngle tilts them toward Direction.

With Direction Top:

Burst Mode	SpreadAngle	Result
Directional	25, 25	A cone of chunks thrown upward. The rows start this way.
Ring	0	A ring thrown flat outward.
Ring	25	A ring thrown outward and 25 degrees upward, as from a ground slam.
Ring	90	Every chunk thrown straight along Direction.

In Ring mode the second number of SpreadAngle is not used.

Chunks and Chunk Scale

• Chunks is at least 1 and at most 32.
• A burst is built for the larger number of the Chunks row. A wide range costs as much as its larger number.
• Chunk Scale 0.5, 1.5 on a RenderTemplate of 2 by 2 by 2 studs gives chunks between 1 and 3 studs across.

The Even dot on Position

With an Even dot on, the chunks of a burst are spaced in equal steps across the range. The spacing is centred, and the two ends of the range are not used.

Position X -4, 4 with its Even dot on and 4 chunks puts the chunks at -3, -1, 1 and 3 studs.

A Part emitter spaces an Even axis differently.

Motion

Row	Kind	Starts at	Unit	What it does
Direction	List	Top		The axis of the throw, as a face of the emitter: Top, Bottom, Front, Back, Left or Right.
SpreadAngle	Two numbers, x, y	25, 25	Degrees	In Directional, the random tilt of each chunk. In Ring, x is the angle of the throw above the flat.
Launch Speed	Graph	30	Studs per second	How hard each chunk is thrown.
Gravity	Two numbers	196.2	Studs per second per second	The downward pull. Each chunk picks its own value.
Bounciness	Two numbers	0.3, 0.5	0 to 1	The share of its speed a chunk keeps when it bounces. At 0 it does not bounce.
Friction	Two numbers	0.3	0 to 1	How much sideways speed is lost at each bounce, and how quickly a chunk slides to a stop.
Tumble	Two numbers	90, 360	Degrees per second	The spin of a chunk in flight, around a random axis and in a random direction.
Sink Out	Switch	On		Chunks at rest sink into the ground at the end of the burst’s life.
Inherit Floor	Switch	Off		A chunk takes the Material and Color of the part it first lands on.
Hit Per Chunk	Switch	Off		Off, On Hit fires once for the burst. On, it fires once for every chunk.

Gravity, Bounciness, Friction and Tumble are picked for each chunk. Every chunk of a burst gets a value of its own.

The hint in the empty SpreadAngle box reads x, y (Ring: x = elevation).

Launch Speed and Gravity

CAUTION

Launch Speed is a graph row, but only its first value is used. Each chunk is thrown once, at that speed. The rest of the graph has no effect. Enter two numbers, such as 50, 80, to give each chunk a speed of its own.

Gravity starts at 196.2, which is Roblox’s own gravity. It is strong, so a throw goes less far than the number suggests. Thrown straight up, a chunk rises by its speed squared, divided by twice the Gravity.

Launch Speed	Gravity	Rise, thrown straight up	Time until it is back at the height of the throw
30	196.2	About 2.3 studs	About 0.3 seconds
50	196.2	About 6.4 studs	About 0.5 seconds
80	196.2	About 16 studs	About 0.8 seconds
30	60	7.5 studs	1 second

With the starting values, a burst is a small hop.

In Ring mode only part of the speed goes upward. At SpreadAngle 30 a chunk thrown at 50 studs per second rises about 1.6 studs. At 80 it rises about 4 studs.

• Gravity always pulls along the world’s down. It does not follow the rotation of the emitter.
• A negative Gravity makes chunks fall upward.
• Bounciness and Friction are held between 0 and 1.

Flight, landing and rest

NOTE

The chunks are not physics objects. The plugin works out where each chunk will land when the burst is fired, then plays the flight back. Nothing depends on the game’s physics. A burst looks the same in Studio and in a running game, and it does not jitter.

Each chunk goes through these stages:

1. It flies an arc under Gravity, tumbling.
2. When the arc meets a surface, the chunk bounces if it still moves fast enough after Bounciness is applied. Friction takes away some of its sideways speed. Its spin changes to a roll in the direction of travel.
3. When it no longer bounces, it slides a short way along the surface and slows. More Friction stops it sooner. As it slides it turns to lie flat on one of its faces, and it prefers a broad face.
4. It rests exactly on the surface. It does not move again until the burst ends.

A chunk that finds no ground keeps falling until the Lifetime ends.

What a chunk collides with

A chunk lands on	A chunk passes through
A part with CanCollide on	A part with CanCollide off
Terrain	Water
	The emitter Part, its RenderTemplate, and the plugin’s own particles
	The Emit Into instance and everything inside it
	Whatever the Hit Filter leaves out
	Other chunks, and characters

• Chunks do not collide with one another. They can overlap where they land.
• The level is read once, when the burst is fired. A door, a platform or a character that moves afterwards is not noticed.
• A chunk keeps the path and the resting place it was given. If the thing under it moves away, the chunk stays hanging there.

Sink Out

With Sink Out on, chunks at rest sink during the last part of the burst’s life.

• Each chunk moves into the surface it rests on. On a slope it sinks into the slope, not straight down.
• The sinking starts slowly and speeds up.
• A chunk sinks deep enough to be fully out of sight.
• A chunk still in flight at that time does not sink.
• With Sink Out on, a Linger shows nothing. The chunks are already under the ground.

With Sink Out off, the chunks stay where they rest and vanish all at once at the end of the Lifetime. Fade them with a Transparency graph for a softer end.

To leave rubble lying, switch Sink Out off and raise Lifetime or Linger.

Inherit Floor

With Inherit Floor on, each chunk takes the Material and Color of the part it lands on. It does so at its own first landing. A burst thrown onto a brick floor becomes brick rubble.

Events

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

On Hit and Hit Per Chunk

For Rocks, On Hit fires when a chunk first touches a surface.

Hit Per Chunk	On Hit fires
Off	Once for the burst, when the first chunk to land makes its first contact.
On	Once for each chunk, at that chunk’s own first contact.

• Later bounces do not fire On Hit.
• A burst whose chunks never touch anything does not fire it.
• A target with Mode AtPosition appears at the point of contact.
• An event script receives the instance that was touched, the position, and the direction the surface faces. See The event script and its payload.

CAUTION

On a Rocks emitter the On Hit block shows the rows Collide, Bounce%, Friction, Spin and HitTick. They have no effect here. The bounce of a chunk is set by Motion ▸ Bounciness and Motion ▸ Friction.

On Emit, On Death and On Destruction

With Mode AtPosition, a target fired by one of these three events appears at the place the burst was thrown from. It does not appear at the chunks.

In an event script, payload.SetColor and payload.SetTransparency act on every chunk of the burst.

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 the chunks land on, and it applies while On Hit is off.

A Rocks emitter as the target of an event

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

• The burst is thrown from the spot of the event.
• Mode AtPosition uses that spot with the Rocks emitter’s own rotation.
• Mode AtCFrame uses that spot, turned the way the event’s particle was turned.
• The Position row still applies 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 chunks of a burst are placed in the Explorer.
Preload Texture	Switch	Off	Keeps every texture the emitter uses loaded, so the first burst does not show blank textures.
Pool	Switch	On	Reuses finished bursts in place of making new ones.

Anim. Steps acts on Color, Brightness, Transparency and Scale. The flight of the chunks does not use it. The flight is played every frame. A value of 0 or less counts as 100.

Emit Into does not change where a burst appears.

CAUTION

The chunks ignore the Emit Into instance and everything inside it. If Emit Into holds the level, the chunks fall through the level.

Nesting

Nesting is described in full on Nesting.

What is put where	Result
A transformed emitter inside the Rocks RenderTemplate	It fires once for each burst, at the place the burst was thrown from. It is not placed on each chunk.
A stock ParticleEmitter, Trail or Beam inside the RenderTemplate	Every chunk has one of its own, because every chunk is a duplicate of the RenderTemplate.
A Rocks emitter inside the RenderTemplate of a Part, Attachment or Model emitter	The burst is thrown from the parent particle.

• The nested emitter’s own Emit, Delay and Duration decide what it does for each burst.
• With Mode Animate and Loop on, nested emitters fire again at every cycle.
• A stock ParticleEmitter in the Part is not carried over by the transform. Put it into the RenderTemplate afterwards.
• A stock Trail or Beam in the RenderTemplate runs only with a Duration above 0. This is the way to a dust trail on every chunk. See Editing stock ParticleEmitters, Trails and Beams.

With the tools

Tool	Effect on a Rocks emitter
Size	Multiplies the Launch Speed graph, Position, Chunk Scale and Gravity.
Time	Multiplies Rate, Tumble and the Launch Speed graph. Divides Lifetime. Multiplies Gravity by the square of the factor.

Size multiplies Gravity together with Launch Speed, so the arcs keep their shape at the new size. It does not change Chunks, Bounciness, Friction, Tumble, SpreadAngle, the Scale graph, or the Size of the RenderTemplate.

Time does not change Bounciness, Friction or Linger. 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 Rocks emitter.

Limits

• A burst has at most 32 chunks.
• Rocks are meant for open ground.
• Chunks do not collide with one another or with characters, and they are not solid.
• The level is read once, when the burst is fired. A chunk does not notice anything that moves afterwards.
• A thin or small obstacle near a chunk’s path can be missed.
• Gravity always acts along the world’s up and down.
• Launch Speed uses only the first value of its graph.
• There is no Link. A burst is thrown from where the emitter is, and does not follow it.
• An edit acts on bursts thrown after it. An Animate loop takes the edit at its next cycle.
• The work for a burst is done when the burst is fired. More chunks and bouncier chunks need more work.
• Once its chunks are at rest, a burst costs almost nothing until it sinks or ends.
• A high Rate with many chunks is the costly combination.