# Sprint and Speed
> UPC Sprint makes the character walk by default and sprint on a button, held or tapped, for a stamina cost. Gameplay tags slow it, and a sprint, a slow and a speed upgrade combine.
Markdown version of https://rigbak.com/docs/universal-player-combat/sprint-and-speed, a page of the Universal Player Combat documentation. Link that page when citing it.
## Set it up (5 minutes)
1. **Add the sprint to the character**
The demo character `BP_UPC_Character` already has a **UPC Sprint** component; skip to step 3 there. In your own character Blueprint, **Add** one (UPC Character Base has none). The character walks at 250 cm/s and sprints at 600.
2. **Grant the sprint button**
The **UPC Sprint Ability** asks for a sprint when the button goes down (held, or tapped to latch); the component decides whether it happens. On a character built on UPC Character Base, add a row to its **Starting Ability Set** (such as the `AbilitySet_MyCharacter` from the [Targeting](https://rigbak.com/docs/universal-player-combat/targeting) quick start): **Ability** `UPCSprintAbility`, **Input Tag** `UPC.Input.Sprint`, **Input Action** `IA_UPC_Sprint` ([Input](https://rigbak.com/docs/universal-player-combat/input#abilities-that-answer-a-key)). A character with its own parent has no such slot: add the same set to **Ability Sets to Grant** on its Default Item's **Equippable** fragment ([Character Setup](https://rigbak.com/docs/universal-player-combat/character-setup#add-more-for-more-features)). The demo's `AbilitySet_UPC_Default` carries it already.
The key comes from a mapping context on the player: the demo controller's `IMC_UPC_Default` maps `IA_UPC_Sprint` to Left Shift. On a controller of your own, add a context that maps it, or put one on the combat style's [Input Mapping](https://rigbak.com/docs/universal-player-combat/combat-styles#tags-and-keys) fragment.
3. **Give the character stamina**
On the character's **UPC Vitals** component (**VitalsComponent** on UPC Character Base), press **+** on **Vitals** for a stamina row that refills ([Vitals](https://rigbak.com/docs/universal-player-combat/vitals)); skip this on a character that has one.
In **VitalsComponent**, under Vitals > Index [1], set:
| Property | Value |
| --- | --- |
| Vital Tag | UPC.Vital.Stamina |
| Max Value | 100.0 |
| Regen Rate Per Second | 15.0 (replaces 0.0) |
| Regen Delay Seconds | 1.5 (replaces 0.0) |
*100 stamina, refilling 15 a second from 1.5 seconds after it last changed.*
4. **Make sprinting cost stamina**
On the UPC Sprint component, set **Stamina Vital** to `UPC.Vital.Stamina`.
In **UPCSprint**, under Stamina, set:
| Property | Value |
| --- | --- |
| Stamina Vital | UPC.Vital.Stamina (replaces None) |
| Stamina Drain Per Second | 10 |
| Min Stamina to Start | 10 |
*Sprinting spends 10 points a second and needs at least 10 in the vital to start.*
5. **Press Play and hold Left Shift while moving**
The character speeds up and stamina drains. Out of stamina it walks; holding the button, it sprints again once 10 points come back.
---
## Tune the sprint
**Details panel: Sprint** (component, in BP_UPC_Character)
**Category: UPC > Sprint**
| Property | Value |
| --- | --- |
| Walk Speed | 250 |
| Sprint Speed | 600 |
| Speed Blend Seconds | 0.35 |
| Min Input Strength | 0.5 |
| Max Sprint Angle | 180 |
| Blocked Tags | UPC.State.Blocking, UPC.State.Encumbered, UPC.State.Overburdened |
| Stop Grace Seconds | 0.2 |
| Request Tag | UPC.State.SprintRequested (advanced) |
| Sprinting Tag | UPC.State.Sprinting (advanced) |
**Category: UPC > Sprint > Stamina**
| Property | Value |
| --- | --- |
| Stamina Vital | None |
| Stamina Drain Per Second | 10 |
| Min Stamina to Start | 10 |
*A new UPC Sprint before step 4: Stamina Vital is None, so sprinting costs nothing, as on the demo character. A component added by hand is named UPCSprint.*
| Setting | Does |
| --- | --- |
| **Walk Speed**, **Sprint Speed** | The two paces in cm/s. Walk Speed replaces the movement component's Max Walk Speed. |
| **Speed Blend Seconds** | How long the change between them takes; 0 changes at once. A combat style's Movement fragment sets it as **Sprint Blend Seconds**. |
| **Min Input Strength** | How far the player pushes the stick to sprint, 0 to 1; a key counts as fully pushed. |
| **Max Sprint Angle** | How far from the facing the movement may point and still sprint. 180 sprints every way; 75 walks a strafe. |
| **Blocked Tags** | Tags that hold the character at walking pace, such as `UPC.State.Blocking` for a raised guard. |
| **Stop Grace Seconds** | How long without movement input counts as stopped, ending a tapped sprint. |
| **Stamina Vital** | The vital a sprint spends. None makes sprinting free. |
| **Stamina Drain Per Second**, **Min Stamina to Start** | Points spent each second, and needed to start. A running sprint carries on until the vital is empty. |
**A tap** shorter than the ability's **Latch Tap Seconds** (0.25 s) keeps the sprint on after release, until the character stops or the button is pressed again; change it in a Blueprint child of `UPCSprintAbility` (0 ends every sprint on release).
**Run without a button** by adding `UPC.State.SprintRequested`, such as from a combat style's **Gameplay Tags** fragment.
---
## React to sprinting
The character carries `UPC.State.Sprinting` at sprint pace, for a camera state ([Camera](https://rigbak.com/docs/universal-player-combat/camera#change-the-camera-while-a-tag-is-on)) or a sprint attack's transition. **On Sprint Changed** fires as a sprint starts or stops, and **Is Sprinting** reads it.
---
## Slow the character by tag: UPC Speed Modifier
Add a **UPC Speed Modifier** component and fill **Speed Scale by Tag** with a tag and its multiplier: 0.2 leaves a fifth of the speed, 0 holds the character still. Tags multiply (0.5 beside 0.2 leaves a tenth), and a parent tag covers its children. A **UPC State Tag Window** holding the tag, such as `UPC.State.Staggered` across a stumble montage, times the slow to the animation ([Animation Integration](https://rigbak.com/docs/universal-player-combat/animation-integration#hold-a-tag-for-part-of-an-animation)).
**Details panel: UPCSpeedModifier** (component, in BP_UPC_Character)
**Category: UPC > Movement**
| Property | Value |
| --- | --- |
| Speed Scale by Tag | 6 Map elements |
| Speed Scale by Tag > key UPC.State.Staggered | 0.2 |
| Speed Scale by Tag > key UPC.State.Blocking | 0.4 |
| Speed Scale by Tag > key UPC.State.Swift | 1.05 |
| Speed Scale by Tag > key UPC.State.Encumbered | 0.85 |
| Speed Scale by Tag > key UPC.State.HeavilyEncumbered | 0.0 |
| Speed Scale by Tag > key UPC.State.Overburdened | 0.0 |
*The demo character slows to a fifth of its speed while staggered and to 40 percent while its guard is up. Carrying 70 percent of the weight limit slows it to 85 percent; carrying the limit or more holds it still. A value above 1 speeds it up: UPC.State.Swift adds 5 percent.*
| Node | Does |
| --- | --- |
| **Set Speed Scale for Tag**, **Remove Speed Scale for Tag** | Change what a tag means during play. |
| **Add Speed Modifier**, **Remove Speed Modifier**, **Has Speed Modifier**, **Clear Speed Modifiers** | Hold a multiplier under an id of your own, for a slow no tag stands for; no ability system needed. |
| **Get Current Speed Scale**, **On Speed Scale Changed** | The combined multiplier, 1 when nothing applies, and an event as it changes. |
---
## How speed changes stack
A sprint, a slow and a move that roots the character all change one walk speed through the character's **UPC Movement Modifiers**, added when something first changes movement:
Starts from. Ends at the walk speed in force.
1. **The character's own walk speed** (Max Walk Speed on the movement component, or Set Base Value): What every change works from while nothing replaces it.
2. **The highest-priority override replaces it** (UPC Sprint at pace priority 0; a Blueprint override at 100 by default): A character carrying a UPC Sprint has its pace here: Walk Speed or Sprint Speed, easing between them.
3. **Every scale multiplies the result** (UPC Speed Modifier, a node's Locomotion Modifier hook, a Blueprint's Scale Value): A slowing tag at 0.5 during a sprint at 600 gives 300.
**To change the speed from a Blueprint:**
- **A permanent upgrade** with a UPC Sprint: set the Sprint component's **Walk Speed** and **Sprint Speed**, such as 275 and 660 for +10 percent. The Sprint component holds the walk speed, so a Set Base Value would not show.
- **A permanent upgrade** without one: **Get Movement Modifiers**, then **Set Base Value** on **Max Walk Speed**.
- **A change of your own for a while:** **Get Movement Modifiers**, then **Scale Value** (Source: Self, Value: Max Walk Speed, Scale: 0.5) or **Override Value**. Later call **Remove Modifiers** with the same Source.
A Max Walk Speed written straight onto the movement component lasts only until the next change.
---
## Debug it
`Log LogUPCCharacter Verbose` raises the sprint's log.
How a sprint is decided (Advanced)
The ability holds `UPC.State.SprintRequested` while the button is down. The **UPC Sprint** component checks every frame whether the character may sprint:
Checked first. Checked last.
1. **Something asks for a sprint** (UPC.State.SprintRequested on the character): The UPC Sprint Ability holds it while its button is down, or after a quick tap until the character stops. Anything else that adds the tag asks the same way.
2. **The character is on the ground** (In the air the pace it left the ground with holds): A jump or a fall neither starts nor ends a sprint.
3. **The stick is pushed far enough, the right way** (Min Input Strength, Max Sprint Angle): Half way by default; a key counts as fully pushed. Every direction sprints until Max Sprint Angle is lowered.
4. **Nothing holds it at walking pace** (Blocked Tags): Any one of the tags on the character keeps it walking, such as a raised guard.
5. **There is stamina to spend** (Stamina Vital, Min Stamina to Start): Starting takes Min Stamina to Start; a running sprint goes on until the vital is empty. No Stamina Vital makes sprinting free.
Every check passing eases the character up to Sprint Speed over Speed Blend Seconds; one failing eases it back to Walk Speed. The character carries UPC.State.Sprinting while it runs at sprint pace.
- The sprint's pace is a walk speed override at the lowest priority, and slows are scales, so the pace keeps easing under an attack that roots the character and resumes where the ease has got to when the attack ends.
- The UPC Input Mapping component sends the second press into the running sprint. Input that starts the ability again instead gets a warning, and the sprint goes on.
- **Is Sprint Requested** is true while something asks for a sprint, allowed or not; **Get Current Speed** gives the pace as it eases. **Request Tag** and **Sprinting Tag**, under the component's advanced arrow, rename the two tags.
Speed Modifier in detail (Advanced)
- An entry below 0 is ignored, so a slow cannot turn into a boost by multiplying with another. **Set Speed Scale for Tag** starts watching a new tag, and **Add Speed Modifier** with an id already held replaces its scale.
- A Blueprint child of the component can override **Combine Speed Scales** to stack another way, such as the harshest only, and **Apply Speed Scale** to scale acceleration or turn rate too.
- **Bind to Owner Ability System** watches the tags again for a pawn that builds or swaps its ability system after the component starts.
The demo
- The demo player's **Sprint** lists `UPC.State.Blocking`, `UPC.State.Encumbered` and `UPC.State.Overburdened` in **Blocked Tags**; its stamina row holds 100 and refills 10 a second after 3 seconds.
- The Freeflow style puts `UPC.State.SprintRequested` on in its Gameplay Tags fragment, so the character runs whenever the stick is pushed past half.
Sprint and speed in multiplayer (Multiplayer)
- The server and the player's machine run the same sprint rules from the same input and tags; a start or stop lands a fraction of a round trip apart, which smoothing absorbs. Only the player's machine ends a tapped sprint.
- Other machines count the character as sprinting while it moves faster than Walk Speed. `UPC.State.Sprinting` sits only on the server and the player's own machine.
- The stamina drain runs on the server.
- Walk speed does not replicate; each machine works it out from the tags it sees, and the Movement Modifiers replicate nothing. Add a Speed Modifier's tag through a gameplay effect or **Add Replicated Loose Gameplay Tag**, or the server and the player disagree about the speed.
C++
- `UUPCSprintComponent::CanSprint` is a `BlueprintNativeEvent`; `HasStopped()` and the native `OnStopped` report the stop a tapped sprint waits for.
- `UUPCSprintAbility` carries `UPC.Ability.ForwardInputWhileActive` in its asset tags, which sends the second press into the running instance.
- `UUPCMovementModifierComponent::FindOrAdd(AActor*)` is Get Movement Modifiers; `OverrideValue`, `ScaleValue`, `OverrideFlag`, `RemoveModifiers(Source)` and `SetBaseValue` work per source. The sprint overrides at `UPCMovementPriority::Pace` (0), a style at `UPCMovementPriority::Style` (100), the approach's facing hold at `UUPCMovementModifierComponent::FacingPriority` (1000).
- `UUPCSpeedModifierComponent::CombineSpeedScales_Implementation` and `ApplySpeedScale_Implementation` are the override points.
Troubleshooting (Advanced)
| Warning or symptom | Fix |
| --- | --- |
| ...does nothing: the owner has no Character Movement component | Put the component on a character. |
| ...heard the press meant to end a latched sprint as a new start | Send the Sprint input through the UPC Input Mapping component, or with **Forward Input Event to Granted Ability** while the sprint runs. |
| The button does nothing | Grant the ability on the input, add a UPC Sprint, or check Blocked Tags. |
| The character sprints only sometimes | Check Min Input Strength and Max Sprint Angle. |
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