# Unreal Engine: Animation and Montages

*2025-08-06*

> Notes taken from the tenth week of Game Programming Foundations


[Last week was UI]({{< relref "/posts/2025/unreal-engine-09-user-interface" >}}); this week, **animation** – and it's a big one: input controls, skeletal meshes, animation graphs, jumping, blend spaces, montages, sockets, notifies, aim offsets, and finally shooting.

This was the first week when everything from the series so far converges into something that actually resembles a game.

Heads up for anyone following the links: this week a **new repository** was started for the second project, since the course moved on from the first:

[sawnoff-studios/character-animation-demo](https://github.com/sawnoff-studios/character-animation-demo)

Here are my notes from this week's content.

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## Input Controls

- By default, mouse controls map to the **X axis** for horizontal look

## Adding a Skeletal Mesh

- Create an **Animations** subfolder for organisation
- Add **Animation Sequences** to it, and set the target skeletal mesh on import

## Animation Blueprint / Graph

- The **State Machine** handles transitions between animations
- Drag and drop animations into it from the **Asset Browser** (lower right)
- On the character Blueprint, set the **Anim Class** (Details panel, right side) to wire up the animation blueprint

## Jumping (Additive Animations)

- `Apply Additive` → plug the additive sequence into the Additive property → control weight via **Set Alpha**
- Create a **jump recovery** Animation Sequence (trim down the Jump Down animation)
- On the animation itself: set **Additive Anim Type** to Local Space, **Base Pose Type** to selected animation frame, **Base Pose Animation** to the jump recovery sequence

## Blend Spaces

- Create a **Blend Space (BS)**, then drag and drop animations onto the grid at the bottom
- In the preview: **Ctrl** moves the sample point along X so you can preview blend speeds
- Back in the state machine: new state → add the blend space → **Get Movement Speed** feeds it
- The **Animation Preview Editor** (lower right) also lets you change movement speed to preview
- Axis settings for direction blends, in degrees:
  - **0** – straight ahead
  - **±90** - right/left
  - **180** – see flag below
- If adjacent axis values are similar, **Wrap Input** avoids a seam at the boundary

## Animation Montages

- Create an **Animation Montage (AM)**
- The **Anim Slot Manager** (lower right) is where slots are added; edit a slot by hovering over the timeline at the bottom, then drag animations onto it
- From the cached pose output pin, use **Layered blend per bone**:
  - Blends two poses with the specified bones
  - **Mesh Space Rotation Blend** blends rotations in mesh space rather than local
  - **Layer Setup → Branch Filters** (right side) select which bones are affected
  - Higher **Blend Depth** → more of the combined animation is used
- New input action (`IA_Attack`) bound to Left Mouse Button → Pressed
- Guarding the attack: only call `PlayAnimMontage()` if `GetCurrentMontage() == nullptr`

## Skeletal Mesh Sockets

Attachment points on a skeletal mesh – used for weapon attachments, clothing, effect placement, held items, sensors, cameras, etc.

- Add a `UStaticMeshComponent` property for the weapon/held object
- Mesh scaled wrong on import? Fix in **Import Settings → Import Uniform Scale**, then **Reimport Base Mesh**
- Set the static mesh collision to **No Collision**
- To create a socket: open the **Skeleton**, choose an Animation Preview on the right, select the bone (e.g. hand) → right-click → **Add Socket**, then right-click → add a preview asset
- Override **OnConstruction** to attach the static meshes to the sockets

## Animation Notifies

- For timing things against the animation (e.g. dealing damage at the moment a swing connects):
  - Sound goes in a **Sounds** folder
  - On the Animation Montage: right-click the timeline → **Add Notify** (or a **Notify State** for a duration)
- On `BP_Enemy`: static mesh, animations, animation blueprint; add `bIsUnderAttack` and `Health` variables
- Damage from the attacker: **SphereTraceMulti()** and **ApplyDamage()**
- The receiver uses the overlap method rather than a line trace: a `UFUNCTION()` raises an `OnOverlapBegin` event; via `MeshComp->GetOwner()`, call the active attack

## Aim Offsets

- Import aiming animations for various directions, convert them to additive en masse:
  - Select all → **Asset Actions → Edit Selection in Property Matrix**
  - Additive Settings: **Additive Anim Type = Mesh Space**, **Base Pose Type = Selected animation frame**, Base Pose Animation = the aiming idle original
  - Save all at once
- Create the **Aim Offset (AO_Aim)**: Horizontal Axis = Yaw (−90 to 90), Vertical Axis = Pitch (−90 to 90), then add animations like a blend space
- New Input Action (`IA_Aim`) on right-mouse button
- `BaseCharacter::Aim()` / `BaseCharacter::IsAttacking()`; `PlayerController::ToggleAim()` calls `ControlledCharacter->Aim()` and supplies pitch/yaw
- Feed `DeltaTime` into `UpdateAnimationProperties()` in the animation blueprint
- In the Animation Graph:
  - New **cached pose** from the Layered blend per bone (Full Body)
  - **Apply Aim Offset** on the full body:
    - **Blend Pose by Boolean**, `Is Aiming` as the active value
    - `AO_Aim` as the True pose (Yaw/Pitch variables fed in)
    - Cached pose (Full Body) as the False pose

## Shooting

- Override the `Attack` function in MainCharacter
- If the character is aiming: get camera location and rotation, determine the trace's start and end, and use **LineTraceSingleByChannel()**
- Note: longer trace distances take longer to evaluate

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## Notes on things that stood out

This week joined everything up. Line traces ([collision week]({{< relref "/posts/2025/unreal-engine-07-collision-detection" >}})), input actions ([Enhanced Input week]({{< relref "/posts/2025/unreal-engine-02-controllers-and-game-modes/" >}})), materials and timelines (weeks [one]({{< relref "/posts/2025/unreal-engine-01-introduction-to-unreal/" >}}) and [six]({{< relref "/posts/2025/unreal-engine-06-communication/" >}})) all resurface inside an animation-driven combat loop.

The big architectural lesson was the notify/socket pairing – the *animation* decides *when* damage happens, the *skeleton* decides *where* the weapon sits – neither belongs in gameplay code.