Impact Knock Back

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Impact Knock Back plays a full-body response when an impact explicitly requests it, most often after a melee counterattack. Use it when the receiving character should briefly give up control to an authored reaction animation; ordinary damage reactions are handled separately by Damage Visualization.

Character Knock Back starts this ability, but it does not deal damage or apply a physical force by itself. Keep the item’s damage actions and add Add Force separately when the hit should also move the target beyond the response clip’s root motion.

Before you begin

  • The receiving character needs Ultimate Character Locomotion, an Animator configured for the UCC parameters, and an animation transition for Ability Index 13 plus the chosen response ID in AbilityIntData.
  • The attacking item needs a working Melee Action with collision detection. Complete a normal hit before adding the response.
  • Decide which Impact Knock Back ID selects each response clip. The value comes from the impact action, not from a field on the ability.
  • The GameObject reported as the impact target must be the character or one of its children so Character Knock Back can find the parent Ultimate Character Locomotion component.

Add the ability to the receiving character

  1. Select the receiving character GameObject.
  2. In Ultimate Character Locomotion, expand Abilities, select the plus button, and add Impact Knock Back.
  3. Move the ability near the top of the list, above every lower-priority action it must interrupt. Impact Knock Back is nonconcurrent and cannot replace an active nonconcurrent ability above it.
  4. Keep Enabled selected and leave Start Type and Stop Type set to Manual. The impact action starts the ability, and Stop Event ends it.
  5. Keep Ability Index Parameter at 13 when using the shipped Animator Controller.
  6. Keep Use Root Motion Position set to True when the response clip contains the intended displacement. The Version 3 default does not override root-motion rotation.
  7. Configure Stop Event. The default disables Wait For Animation Event and uses a Duration of 0.2 seconds.

Do not add an input name. A player button is not part of this workflow.

Add Character Knock Back to the melee item

  1. Select the melee item GameObject and its Melee Action.
  2. Expand Impact Module Group and select the enabled Generic Melee Impact Module that already handles the intended hit. If the item does not have one, use the plus button to add it.
  3. Use Substate Index or Attack ID when only a particular attack should cause the response. Their default value of -1 accepts every substate or attack ID.
  4. Confirm the module’s Conditions describe a hit that should reach Impact Actions rather than Fail Impact Actions.
  5. In Impact Actions, select the plus button and add Character Knock Back.
  6. Set Impact Knock Back ID to the value expected by the receiving character’s Animator transition.
  7. Keep Delay at 0 for an immediate reaction, or set a deliberate delay when the response should begin later.
  8. Add Add Force to the same Impact Actions only when the hit also needs a physics-driven push.

A newly added Generic Melee Impact Module contains the standard damage, surface-effect, and impact-event actions. Remove actions that another enabled module already invokes so the target is not damaged twice.

Choose the response behavior

Select the animation with an ID

When Character Knock Back hits a UCC character, Impact Knock Back ID becomes the ability’s AbilityIntData. The shipped ability supplies Ability Index 13. The Animator needs a transition whose two conditions match those values.

Use a separate ID for each authored response, such as left, right, light, or heavy. The IDs are project-defined; assigning a value without a matching Animator transition starts the ability but produces no visible response.

Use the Generic Melee Impact Module’s Substate Index and Attack ID filters to decide which attack sends a particular response ID. This keeps a counterattack-specific reaction from playing on every swing.

Choose root motion or an added force

Use Root Motion Position: True lets the full-body response clip move the character through the controller. This is the Version 3 default. Use an authored root-motion clip when its displacement must stay synchronized with the pose.

Character Knock Back does not add force. Add an Add Force impact action for a physical push, including an in-place response clip, or combine it carefully with root motion when both are intentional. Test the total displacement rather than assuming the animation and force will not stack.

The ability leaves Allow Positional Input and Allow Rotational Input enabled by default. Disable either inherited setting when the response must ignore that form of player input for its entire active window.

End by duration or animation event

Expand Stop Event and choose one completion mode:

  • Leave Wait For Animation Event disabled to stop after Duration. The default is 0.2 seconds. Tune this to the point where other gameplay abilities may resume, which may be earlier than the clip’s final blend-out frame.
  • Enable Wait For Animation Event to stop only when the active response clip sends OnAnimatorImpactKnockBackComplete. Add that exact event to every response clip that can play.

These modes do not fall back to one another. A missing event leaves the ability active.

Decide what the reaction interrupts

Place Impact Knock Back near the top of Abilities so it can replace the intended lower-priority nonconcurrent abilities. Starting it explicitly stops an active Use item ability on the receiving character. While the response is active, its own block rule rejects new abilities except Ragdoll. If a manually started Ragdoll must interrupt this response, place Ragdoll above Impact Knock Back; the exception does not bypass normal list priority.

How Impact Knock Back runs

On a qualifying hit, the Generic Melee Impact Module runs its Impact Actions. Character Knock Back reads the reported impact GameObject, finds Ultimate Character Locomotion on that object or a parent, and looks up the first Impact Knock Back ability on the receiving character. If either component is missing, the action ends without starting a response.

Character Knock Back passes Impact Knock Back ID to the ability. The ability exposes that value as AbilityIntData, starts manually, forces root-motion position by default, and begins waiting on Stop Event. The Animator then selects the matching full-body response with Ability Index 13 and the received ID.

When the configured duration elapses or OnAnimatorImpactKnockBackComplete arrives, the ability stops and releases its priority. Damage, surface effects, and an added force continue to be owned by their separate impact actions.

Verify in Play Mode

  1. Keep the receiving character’s Ultimate Character Locomotion Inspector and Animator window visible.
  2. Trigger the melee attack whose Substate Index or Attack ID matches the configured Generic Melee Impact Module. Confirm Impact Knock Back displays (Active).
  3. Confirm Animator Ability Index becomes 13, AbilityIntData matches Impact Knock Back ID, and the intended full-body response plays.
  4. Start an item Use or another lower-priority nonconcurrent ability on the receiver before the hit. Confirm the response interrupts it and another normal ability cannot start until the response ends.
  5. Trigger an attack that does not match the configured Substate Index or Attack ID. Confirm Impact Knock Back does not start from that module.
  6. In duration mode, confirm (Active) disappears after the configured Duration. In event mode, confirm the response clip sends OnAnimatorImpactKnockBackComplete at the intended frame.
  7. If Add Force is present, confirm the physical push occurs once and produces the intended total displacement with the clip’s root motion.

Troubleshoot Impact Knock Back

Symptom Check Fix
The melee hit lands but the ability never starts. Confirm Character Knock Back is in the active module’s Impact Actions, its Conditions pass, and the Substate Index or Attack ID matches. Move the action to the correct Generic Melee Impact Module or correct the filter and condition.
The impact action runs but cannot find the receiver. The reported impact GameObject may not be the character or a child of the GameObject with Ultimate Character Locomotion. Put the hit collider under the character hierarchy or correct the collision target reported by the melee setup.
A receiver with UCC still does not react. Impact Knock Back may be missing, disabled, or below an active higher-priority nonconcurrent ability. Add and enable the ability, then move it above the action it must interrupt.
Impact Knock Back becomes active but no animation plays. The Animator may lack Ability Index 13, the selected AbilityIntData transition, or the required UCC parameters. Match Ability Index Parameter and Impact Knock Back ID to a valid Animator transition.
The wrong response clip plays. The item’s Impact Knock Back ID may point to another AbilityIntData branch. Compare the action’s ID with the transition conditions and give each response a deliberate ID.
The response ends too early or too late. Check whether Stop Event uses Duration or the Animator event. Retune Duration or move OnAnimatorImpactKnockBackComplete to the intended release frame.
The response never ends. Wait For Animation Event is enabled, but the active clip does not send the exact completion event. Add OnAnimatorImpactKnockBackComplete to every reachable response clip or switch deliberately to Duration mode.
The animation plays but the target is not pushed. Character Knock Back starts the ability but applies no force. The clip may also be in-place. Use a root-motion response clip or add and configure Add Force as a separate impact action.
The target takes damage twice. A new Generic Melee Impact Module may duplicate the standard damage actions already present in another enabled module. Reuse the existing module or remove the duplicate Simple Damage action.
  • Melee explains the Melee Action and its module groups.
  • Impact Actions covers conditions, delays, damage, force, and other impact results.
  • Damage Visualization is the additive, damage-event-driven alternative for ordinary hit reactions.
  • Ragdoll handles a physics-driven body response rather than an authored full-body knock-back clip.
  • Animator Parameters explains Ability Index and AbilityIntData.
  • Animation Event Trigger explains duration and Animator-event completion modes.
  • Abilities explains manual activation, list priority, and nonconcurrent abilities.

Developer reference

Impact Knock Back has these released Version 3 defaults and runtime rules:

  • Start Type: Manual; Stop Type: Manual.
  • Ability Index Parameter: 13.
  • Use Root Motion Position: True; Use Root Motion Rotation: No Override.
  • Allow Positional Input and Allow Rotational Input: enabled.
  • Stop Event: Wait For Animation Event disabled and Duration 0.2.
  • StartKnockBackResponse(int id) stores the response ID and calls StartAbility; AbilityIntData returns that stored ID.
  • OnAnimatorImpactKnockBackComplete completes Stop Event when animation-event mode is enabled.
  • ShouldBlockAbilityStart blocks every starting ability except Ragdoll while Impact Knock Back is active.
  • ShouldStopActiveAbility explicitly stops an active Items.Use when the response starts.

Character Knock Back is an Impact Action with Enabled on, Delay 0, Allow Multi Hits off, and Impact Knock Back ID 0 by default. It resolves the impacted object’s parent Ultimate Character Locomotion, retrieves its first ImpactKnockBack ability, and calls StartKnockBackResponse. It does not apply damage or force.