UE5 Ragdoll 101: Knock a Character Down with a Physics Asset

When an enemy's HP reaches 0, instead of removing it on the spot, you want its knees to buckle and the body to fall to the floor. On a slope, you want it to roll with the incline. Building that motion with physics is a ragdoll .

While walking, animation builds the pose; when falling, the body's motion is left to gravity and collisions. This article uses the Third Person template's character to try fall on R → add a push → disappear after eight seconds .

What You'll Learn

• The Physics Asset's role in driving a body with physics
• How to inspect bodies and joints in the editor
• Switching between Character movement and Mesh physics
• How to push a falling body and where to look when it misbehaves

A ragdoll leaves body motion to physics

A walk animation changes the positions and rotations of hips, knees, feet, and so on in sequence to produce a walking figure. In a ragdoll, each part of the body falls under gravity, hits the floor, and pulls on what it is attached to. The falling pose comes out of that.

"Stopping the animation" alone does not make the body collapse. You need a physics body to hand the motion to. The Physics Asset we look at next provides it.

How it falls varies with the pose at that moment, the direction pushed, the floor's shape, and more. That differs from playing the same death animation every time. You get motion where a foot catches on stairs or the body rolls down a slope, adapted to the terrain.

It does not always fall into the pose you intend, though. A boss's scripted exit suits animation and terrain-driven collapse suits a ragdoll, so choose by the effect. There are ways to mix the two, but start from switching the whole body to physics.

A Physics Asset holds "body shapes" and "connections"

A character's Skeletal Mesh is a model whose shape changes with bone motion. A Bone is part of the framework deciding the position and rotation of the hips, arms, and so on.

Bones alone do not decide collision with the floor or weight. So a Physics Asset configures the shapes used in physics calculations and how they connect.

Element	What it decides	Example on a body
Body	The colliding shape and mass	A capsule around the torso, a sphere around the head
Constraint	How bodies separate and bend relative to each other	The arm not leaving the shoulder and bending within a set range

Rather than tracing the visible silhouette in detail, bodies wrap the body in simple shapes such as spheres, capsules, and boxes. Constraints act like joints, connecting separate parts so they move as one body.

The number of bones and the number of physics bodies are not necessarily the same. Whether you want per-finger detail or one body for the whole hand depends on the motion you need. For a first exercise, we use the Physics Asset that ships with the standard character.

Preparation: try it small on the standard character

What we need here is a character with bones and a Physics Asset. The white Cube used in earlier input exercises has no bones, so we start in a separate practice project . The blue figure in the diagrams illustrates the mechanism; we use the template's own model in practice.

1. Duplicate the Third Person character

1. Choose "Games → Third Person" for a new project and build it with Blueprint. Choose None where Variants are offered.
2. Play and confirm WASD movement and Space jumping.
3. Find BP_ThirdPersonCharacter in the Content Browser, duplicate it, and name it BP_RagdollPractice .
4. Open the GameMode in use from the level's "World Settings → GameMode". Change Default Pawn Class to BP_RagdollPractice.
5. Compile, save, and Play. The duplicated character moving the same way means you are ready.

Default Pawn Class is the kind of character spawned for the player. Rather than hand-placing another character in the level, it spawns from the same PlayerStart as the template. If the original character appears, also check the level's GameMode Override.

2. Open the Physics Asset from the Mesh

Select Mesh (CharacterMesh0) in BP_RagdollPractice's Components. That is the Skeletal Mesh Component handling the body's appearance.

Open the assigned model from the Skeletal Mesh Asset field in the Details panel. Search for Physics Asset in that model's Asset Details and open the configured asset. Entering from here avoids accidentally inspecting a similarly named model's Physics Asset.

In the Physics Asset Editor, look at the bodies wrapping the body and the joints connecting them. Select the body near the hips and note the corresponding bone name. On the standard mannequin, pelvis is the hip bone. We use that name for the push later.

Press Simulate in the toolbar and confirm the body moves under gravity. Stop before editing settings. Try the shipped settings first, and to adjust, duplicate the Physics Asset and assign it to Physics Asset Override on BP_RagdollPractice's Mesh before changing it. Override is the field for overriding the settings used by this Mesh individually.

If the body jitters violently at this stage, investigate the Physics Asset before the game Blueprint. The troubleshooting section below covers how to tell them apart.

Hands-On: collapse on the R key

Rather than combining with HP and attacks right away, first make R knock it down. We edit BP_RagdollPractice.

1. Add the R key input

Create the Input Action IA_RagdollPractice with Value Type Digital (Bool) and empty Modifiers and Triggers.

Open the Input Mapping Context the template uses for movement (IMC_Default or similar), add IA_RagdollPractice to Mappings, and assign the R key. If you cannot find it, filter for Input Mapping Contexts in the Content Browser and check which registers IA_Move and IA_Jump. Keep the existing movement and camera assignments.

If the relationship between input actions and keys is unclear, the Enhanced Input introduction covers how these two asset types relate.

Place IA_RagdollPractice in the event graph, wire Started into Print String, and display "R received". Play, click the screen, and R producing the display means input is ready.

2. Name the falling logic

Create a Custom Event in the event graph and name it StartPracticeRagdoll . That is your own entry point for "start falling", not a standard UE node name.

Compile, right-click the graph, and search for StartPracticeRagdoll to place the calling node. Remove the Print String wired to IA_RagdollPractice's Started and connect this call instead. On the Custom Event's definition side, wire the white output into Do Once .

Do Once passes only the first time through. We use it so mashing R does not apply force repeatedly or extend the cleanup time. Start Closed is off and Reset is unconnected.

3. Stop the walking components

Separately from the body Mesh, a Character has Character Movement handling movement and a Capsule Component serving as movement collision.

Leaving those working normally while the body goes to physics makes only the visuals fall while the player's movement logic remains. So we stop normal movement first.

Drag Character Movement from Components into the graph and create Disable Movement from that reference. Wire the Do Once's Completed you placed earlier into this node's exec input. You do not need to add a Do Once per diagram.

Next create Set Collision Enabled from the Capsule Component with New Type set to No Collision. Wire it from Disable Movement's exec output. The Capsule stays in place but no longer collides with the falling body or surroundings.

4. Switch the Mesh to physics

Now drag the Mesh from Components into the graph and create these two nodes in order.

Node	Target	Setting
Set Collision Profile Name	Mesh	In Collision Profile Name = Ragdoll
Set Simulate Physics	Mesh	Simulate = on

The order is the Capsule's Set Collision Enabled → the Mesh's Set Collision Profile Name → the Mesh's Set Simulate Physics. We disable the Capsule's collision and drive the Mesh, so do not swap the Targets.

A Collision Profile is a name given to a set of collision settings. Ragdoll is the standard preset for physics-driven Skeletal Meshes. Custom settings are possible, but we use the standard values in this exercise.

Turning Set Simulate Physics on starts the bodies in the Mesh's Physics Asset moving under physics. Play here and press R to confirm the body collapses to the floor. Pressing WASD after falling and not returning to normal walking means this stage works.

5. Clean up after eight seconds

Create Set Life Span from Set Simulate Physics' exec output with Target=self and In Lifespan=8. Self is the whole BP_RagdollPractice Actor, not a body part.

Life Span is the remaining lifetime. It destroys the whole Actor eight seconds after this node is called. That is cleanup so fallen bodies do not linger and you can move to the next fight.

Play and press R to see the fallen body disappear after eight seconds. Since this exercise destroys your own character, stop Play and start over for the next check.

The camera is attached to the original Capsule, so it does not automatically follow the falling, moving Mesh. Try short-distance motion on flat ground first.

Push the falling body with Add Impulse

Gravity alone makes it fall, but to convey the momentum of a hit, add Add Impulse . An impulse gives momentary push and motion. It is not continuous force, so we call it once as it starts to fall.

1. Push along the body's forward, slightly upward

First build the input value.

Push value = my forward vector × 500 + (0, 0, 200)

A Vector bundles three numbers, X, Y, and Z. Get Actor Forward Vector (Target=self) gives a forward direction of length 1, multiplied by 500 as a Float, the numeric type handling decimals. Add the Vector (0, 0, 200) to that result.

Forward is the direction the character currently faces, not a fixed world +X. Z is vertical, so adding 200 also introduces upward motion.

Create Add Impulse from the Mesh reference and insert it between Set Simulate Physics and Set Life Span.

Input	Value / connection
Target	Mesh
Impulse	The Add result above
Bone Name	pelvis
Vel Change	On

Specify the bone name corresponding to the hip body you confirmed in the Physics Asset for Bone Name. Using another model means substituting its name. None does not mean "apply nowhere"; it specifies the root-side body.

Turning Vel Change on passes the value as a velocity change independent of mass. Here it applies 500 cm/s forward and 200 cm/s upward to the hip body. The whole body's motion is also influenced by bodies and joints attached to the hips and by floor collisions.

2. Compare push strengths

Play, stand still somewhere flat and open, and press R. See whether the body is pushed forward as it falls. Then lower the forward 500 to 200 and compare how far it is pushed.

Even the same value falls differently with pose and contact. It is not a setting where "this value always lands it face up". Confirm the difference in momentum first, then find a value matching your attack.

Hook it into what happens when HP reaches 0

Once R knocks it down, you can change what triggers StartPracticeRagdoll to HP reaching 0.

The health and damage article built BP_Damageable, a box with HP. That box is a Static Mesh, so it will not become a limbed ragdoll as is. Give the character health logic and change its final action.

On the Character side, the flow becomes subtract Damage → check whether HP is 0 → call StartPracticeRagdoll. Remove the Destroy Actor at the moment HP reaches 0 and destroy after the falling effect instead. Here, Set Life Span removes it after eight seconds.

The push direction at this point is the character's own forward. To make an enemy fall "in the direction it was shot from", pass that direction from the attacker. For a Line Trace, End minus Start normalized to length 1 is a candidate; for a real projectile, the direction it was traveling.

A Hit Result's Normal is the direction the hit surface faces. It is not necessarily the projectile's direction of travel, so do not use it directly as the attack direction.

Checks for jittering and falling through the floor

When something goes wrong, separate whether it happens in the Physics Asset Editor alone or only in game . That lets you investigate the asset deciding how it falls separately from the logic switching things during play.

Symptom	Where to look first
Pressing R does nothing	Whether the input-check Print String appears, and the call from Started
It stands there unmoving	Whether Set Simulate Physics' Target is the Mesh, whether a Physics Asset and bodies exist
The body falls through the floor	Whether the Mesh's physics collision is enabled and the floor has collision that Blocks it
The body jitters violently	Overlap between colliding bodies, joints, collision with the Capsule
It falls but is not pushed	Whether Add Impulse is called after physics is on, the hip bone name and body
The body does not disappear	Whether Set Life Span's Target is self, whether the value is 8, whether the exec line reaches it

Overlapping bodies with collision enabled between them try to push each other apart. Joints, meanwhile, try to hold the body together, which causes violent jitter. Check the problem body's size and position and collision between adjacent bodies in the Physics Asset Editor.

Simulating with gravity off (No Gravity) also helps isolate things. If motion is disturbed before it even falls to the floor, investigate body and joint settings first. Conversely, if it is fine in the editor and disturbed only in game, check overlaps with the Capsule and nearby objects.

For slight jitter, tuning Damping , which gradually reduces motion, can help. Do not raise values so far that they hide the cause, though. Settle collision and joints first, then tune how it comes to rest.

Bonus: moving part of the body, and getting up

"Below" is a range following bone connections

Set All Bodies Below Simulate Physics switches bodies from a specified bone onward to physics. Below here means the child side in the bone hierarchy, not what is lower on screen .

With shoulder → upper arm → forearm → hand connected, starting from the upper arm targets the arm side. Include Self decides whether the starting bone itself is included.

That alone does not complete a mechanism for "an arm going limp naturally while walking", though. Beyond which bodies and joints move, you also design how the animated pose and the physics result mix. It is a subject for after you understand the full-body example.

Getting up means aligning the body and the movement reference

Even when the fallen Mesh rolls, the Capsule that was the movement reference stays where it was. Turning physics off and restoring walking alone offsets the body from the movement position or snaps the pose.

Recovery means handling the Capsule's repositioning, the Mesh's position and pose, collision, movement, and a get-up animation together. Building it as a separate stage from this "fall and disappear" logic makes it easier to confirm.

When leaving fallen bodies in place, decide how many and for how long. Physics sleep rests calculation for settled bodies, but collisions can wake them. Distinguish it from an operation that pins them permanently.

Summary

A Physics Asset has bodies representing parts of the body and joints connecting them. Becoming a ragdoll makes that body move under gravity and collisions, producing the falling pose.

Start by inspecting the shipped Physics Asset and knocking it down with R. Confirming falling, being pushed, and disappearing over time in order also helps you tell how far things got when you integrate it into what happens at 0 HP.

Reference: Third Person template, Skeletal Mesh physics switching, Testing Physics Assets, Troubleshooting Physics Asset errors, Add Impulse, Collision settings.