Exercise 13: A ground slam that throws rubble

Purpose. To throw chunks of rubble outward from a point, have them land and settle on the floor, and puff dust where each one lands.

Sparks pass through the floor. Rubble must not: it has to arc, hit the ground, bounce once or twice, and lie still. The Rocks emitter does that. It is made with Transform as, like the Camera Shake of Exercise 11 and the Lightning of Exercise 12.

Before starting

• The workspace has a floor that parts can collide with.
• One new Part named Rubble sits a little above the floor, with Size 2, 2, 2, Material Slate and a grey colour. Every chunk will be a duplicate of this Part.
• The Sparks emitter from Exercise 12 is in the workspace. It will serve as the dust.

Procedure

Steps 1, 2, 7 and 8 repeat earlier exercises.

Step	Control	Action	Result
1	Rubble	Select. Press ▾ beside Transform, then Transform as Rocks.	Rubble turns invisible. The Emit box reads 1.
2	HUD ▸ Emit button	Press	Between six and ten chunks of different sizes hop about 2 studs into the air, fall, and come to rest on the floor. Near the end of their three seconds they sink into the floor and are gone.
3	Properties ▸ Motion ▸ Launch Speed	Enter 50, 80	No change yet.
4	Properties ▸ Spawn ▸ Burst Mode	Set to Ring	No change yet.
5	Properties ▸ Motion ▸ SpreadAngle	Enter 30	No change yet.
6	HUD ▸ Emit button	Press	The chunks leave in a ring, evenly spaced around Rubble, thrown outward and 30 degrees upward. Each rises between about 1.5 and 4 studs, lands some way off, bounces, slides, and lies flat on one face.
7	Properties ▸ Events ▸ On Hit	Expand Events. Switch On Hit on.	The rows of the On Hit block appear.
8	On Hit ▸ Emit ▸ …	Press. Click Sparks. Press Set.	The Emit row shows the path to Sparks.
9	HUD ▸ Emit button	Press	One burst of sparks goes off, at the spot where the first chunk lands.
10	Properties ▸ Motion ▸ Hit Per Chunk	Switch on	No change yet.
11	HUD ▸ Emit button	Press	Every chunk throws its own burst of sparks where it first lands.

NOTE

The chunks are not physics objects. The plugin works out where each chunk will land at the moment the burst is fired, then plays the flight back. A chunk does not notice anything that moves afterwards, and chunks do not collide with one another or with characters.

CAUTION

Launch Speed is a graph row, but only its first value is used. Each chunk is thrown once, at that speed. Type two numbers to give each chunk a speed of its own.

CAUTION

Transform as Rocks switches off CanCollide on the Rubble Part itself.

What the steps did

A Rocks emitter throws a burst of chunks. One particle is one whole burst, so an Emit count of 2 means two bursts. Each chunk is a duplicate of the Part, at a size of its own.

Row	Starts at	What it sets
Spawn ▸ Chunks	6, 10	How many chunks are in a burst. At most 32.
Spawn ▸ Chunk Scale	0.5, 1.5	The size of each chunk, as a multiple of the Part’s size. A 2 stud Part gives chunks from 1 to 3 studs.
Spawn ▸ Burst Mode	Directional	Directional throws every chunk the same way, spread by SpreadAngle. Ring spaces the chunks evenly in a circle and throws them outward.
Motion ▸ Launch Speed	30	How hard each chunk is thrown, in studs per second.
Motion ▸ Gravity	196.2	The downward pull, in studs per second per second. This is Roblox’s own gravity.
Motion ▸ Bounciness	0.3, 0.5	The share of its speed a chunk keeps at each bounce, from 0 to 1.
Motion ▸ Sink Out	On	Chunks at rest sink into the surface under them at the end of the burst’s life.
Motion ▸ Hit Per Chunk	Off	Off, On Hit fires once per burst, at the first landing. On, it fires once for every chunk.

Gravity here is strong, so a throw goes less far than the number suggests. Thrown straight up at 30 studs per second, a chunk rises about 2.3 studs. At 80 it rises about 16.

In Ring mode, the first number of SpreadAngle is the angle of the throw above the flat: 0 is flat outward, 90 is straight along Direction.

The event at steps 7 and 8 is the same On Hit as in Exercise 12, picked the same way. For Rocks it fires when a chunk first touches a surface.

If the result differs

Symptom	Cause	Action
The chunks fall through the floor	The floor has CanCollide off.	Switch CanCollide on for the floor.
The chunks barely leave the ground	Launch Speed is still 30.	Repeat step 3.
The chunks vanish without sinking	Sink Out is off.	Switch it on, or fade them with a Transparency graph.
No sparks at all	The chunks did not touch anything, or the On Hit block has no emitter picked.	Repeat step 8.
The chunks lie about but no rubble remains afterwards	Sink Out removes it.	Switch Sink Out off and raise Lifetime or Linger.

Variations

Change	Result
Motion ▸ Inherit Floor on	Each chunk takes the material and colour of the part it lands on, so the rubble matches the floor.
Transform a MeshPart rock in place of the block	Every chunk is that mesh, at a size of its own.
Motion ▸ Gravity 60	A slow, floating throw.
Emission ▸ Timescale -1	The burst plays backwards. The chunks start at rest and fly back together.
Motion ▸ Tumble 0	The chunks fly without spinning.
Burst Mode Directional, Direction Front, SpreadAngle 15	Debris sprayed one way, as from a wall struck from behind.

Log

New in this exercise	Transform as Rocks. Burst Mode. Launch Speed. Hit Per Chunk.
Done before	Transform as (Exercises 11 and 12). SpreadAngle (Exercises 2, 4, 9 and 10). The On Hit event and its picker (Exercise 12). The Emit button (seven times).
Carried forward	Nothing.