Movers

GS_MoverComponent (base — mode-aware activation, tick management)
  └── GS_PhysicsMoverComponent (adds RigidBody cache + validity check)
        ├── GS_3DFreeMoverComponent    (mode: "Free")
        └── GS_3DSlideMoverComponent   (mode: "Slide")

#pragma once
#include <Source/Unit/Mover/GS_PhysicsMoverComponent.h>

namespace MyProject
{
    class MyCustomMover : public GS_Unit::GS_PhysicsMoverComponent
    {
    public:
        AZ_COMPONENT_DECL(MyCustomMover);
        static void Reflect(AZ::ReflectContext* context);

    protected:
        void Activate() override;

        void HandleMovement() override;
        void HandleRotation() override;

    private:
        // Mode name must be set in Activate():
        // m_moveModeName = "MyMode";
        // m_rotateModeName = "MyMode";
    };
}

void MyCustomMover::HandleMovement()
{
    AZ::Vector3* groundedInput = nullptr;
    GS_Unit::MoverContextRequestBus::EventResult(
        groundedInput, GetEntityId(),
        &GS_Unit::MoverContextRequestBus::Events::GetGroundMoveInputAxis
    );

    if (!groundedInput || groundedInput->IsZero()) return;

    AZ::Vector3 targetVelocity = *groundedInput * activeProfile->moveSpeed;
    m_rigidBody->SetLinearVelocity(targetVelocity);
}

1 - 3D Free Mover

GS_3DFreeMoverComponent is the standard mover for walking characters. It reads the ground-projected input vector from the MoverContext, applies optional slope attenuation, computes a destination velocity, and drives the rigid body via AccelerationSpringDamper. Rotation is handled separately using QuaternionSpringDamper to face the last non-zero movement direction.

Mode names: "Free" (both movement and rotation)

For usage guides and setup examples, see The Basics: GS_Unit.

Contents

• How It Works
• Slope Slowdown
• Speed Calculation
• Editor-Exposed Settings
• Extension Guide
• See Also

How It Works

HandleMovement()

Called each post-physics tick while movement mode is "Free":

1. Reads groundedMoveInput pointer from MoverContextRequestBus::GetGroundMoveInputAxis.
2. If EnableSlopeSlowdown is true, attenuates the input vector on steep slopes (see Slope Slowdown).
3. Multiplies the attenuated direction by CalculateSpeed() to get destinationVelocity.
4. Fetches rigidBody->GetLinearVelocity() as the current velocity.
5. Calls GS_Core::Springs::AccelerationSpringDamper(position, velocity, cachedAcceleration, destinationVelocity, moveHalflife, delta).
6. Applies the result: rigidBody->SetLinearVelocity(velocity).

The cachedAcceleration is a member field that persists between frames to produce smooth acceleration response even on sudden direction changes.

HandleRotation()

1. Reads groundedMoveInput from the MoverContext.
2. Updates lastDirection only when groundedMoveInput is non-zero — so the unit keeps facing the last direction when stopped.
3. Computes target yaw from lastDirection using atan2f.
4. Calls GS_Core::Springs::QuaternionSpringDamper(currentRotation, cachedAngularVelocity, targetRotation, rotateHalflife, delta).
5. Applies cachedAngularVelocity.Z to rigidBody->SetAngularVelocity().

StopMovement State

When ContextStateChanged("StopMovement", 1) fires, the mover zeros both velocity and cached acceleration, then clears the state back to 0. This allows other systems (e.g. landing from a jump, ability wind-up) to cleanly halt the unit.

Slope Slowdown

When EnableSlopeSlowdown is true, the mover reduces movement speed as the slope angle increases toward maxWalkAngle. The attenuation curve uses an exponent applied to the dot product of the movement direction against the uphill slope direction:

attenuation = 1.0 - uphillSlowStrength * pow(dot(moveDir, slopeDir), uphillSlowExponent)
              × remap(slopeAngle, startSlowAngle, maxWalkAngle, 0, 1)

The slowdown begins at startSlowAngle degrees and reaches maximum reduction at maxWalkAngle. At or beyond maxWalkAngle, the grounder will switch the unit to "Slide" mode regardless.

Speed Calculation

CalculateSpeed() lerps curSpeed toward activeProfile->moveSpeed each frame:

curSpeed = AZ::Lerp(curSpeed, activeProfile->moveSpeed, expf(-speedChangeSmoothing * delta));

speedChangeSmoothing is read from activeProfile. This produces a smooth speed transition when the movement profile changes (e.g. entering a slow zone).

Editor-Exposed Settings

Extension Guide

Extend GS_3DFreeMoverComponent to override movement or rotation behavior while keeping the base spring physics.

#pragma once
#include <Source/Unit/Mover/GS_3DFreeMoverComponent.h>

namespace MyProject
{
    class MyFreeMove : public GS_Unit::GS_3DFreeMoverComponent
    {
    public:
        AZ_COMPONENT_DECL(MyFreeMove);
        static void Reflect(AZ::ReflectContext* context);

    protected:
        void HandleMovement() override;
    };
}

void MyFreeMove::HandleMovement()
{
    // Call base for standard spring movement
    GS_3DFreeMoverComponent::HandleMovement();

    // Add custom post-processing (e.g. strafe penalty, footstep IK correction)
}

See Also

• Movers — Mover base class and class hierarchy
• GS_3DSlideMoverComponent — Activated automatically when slope exceeds max walk angle
• Mover Context — Provides groundedMoveInput and activeProfile
• Springs Utility — AccelerationSpringDamper and QuaternionSpringDamper used internally

Get GS_Unit

GS_Unit — Explore this gem on the product page and add it to your project.

2 - Slide Mover

GS_3DSlideMoverComponent handles slope-sliding locomotion. It activates automatically when the grounder detects a slope angle exceeding maxWalkAngle, and deactivates when the slope eases or the unit slows enough to recover.

Mode names: "Slide" (both movement and rotation)

For usage guides and setup examples, see The Basics: GS_Unit.

Contents

• How It Works
• Finish Sliding
• Editor-Exposed Settings
• Extension Guide
• See Also

How It Works

HandleMovement()

Called each post-physics tick while movement mode is "Slide":

1. Reads slopeDir from MoverContextRequestBus::GetSlopeDirection.
2. Computes destinationVelocity = slopeDir * baseSlideSpeed.
3. If EnableInputSlideResistance is true, reads groundedMoveInput and applies an opposing influence:

   destinationVelocity += groundedMoveInput * InputResistanceInfluence
   

   This allows the player to push slightly against or across the slide direction.
4. Fetches rigidBody->GetLinearVelocity() as the current velocity.
5. Calls GS_Core::Springs::AccelerationSpringDamper(position, velocity, cachedAcceleration, destinationVelocity, moveHalflife, delta).
6. Applies the result: rigidBody->SetLinearVelocity(velocity).
7. Calls FinishSliding() to check whether the slide should end.

HandleRotation()

1. Reads slopeDir from the MoverContext.
2. Computes target yaw from slope direction using atan2f — unit faces down the slope.
3. Calls GS_Core::Springs::QuaternionSpringDamper(currentRotation, cachedAngularVelocity, targetRotation, rotateHalflife, delta).
4. Applies cachedAngularVelocity.Z to rigidBody->SetAngularVelocity().

Finish Sliding

FinishSliding() is called every movement tick. It returns true and triggers recovery when both conditions are met:

• The current slope angle is below minSlideAngle
• The unit’s current speed is below minSpeedToStop

On recovery:

MoverContextRequestBus::ChangeMovementMode(recoveryMoveMode);
MoverContextRequestBus::ChangeRotationMode(recoveryRotateMode);

Both modes default to "Free", returning the unit to standard locomotion.

Editor-Exposed Settings

Extension Guide

Extend GS_3DSlideMoverComponent to override slide behavior while keeping the base spring physics and recovery logic.

#pragma once
#include <Source/Unit/Mover/GS_3DSlideMoverComponent.h>

namespace MyProject
{
    class MySlide : public GS_Unit::GS_3DSlideMoverComponent
    {
    public:
        AZ_COMPONENT_DECL(MySlide);
        static void Reflect(AZ::ReflectContext* context);

    protected:
        void HandleMovement() override;
    };
}

void MySlide::HandleMovement()
{
    // Call base for standard slope physics
    GS_3DSlideMoverComponent::HandleMovement();

    // Add custom post-processing (e.g. audio trigger, particle effect on slide)
}

See Also

• Movers — Mover base class and class hierarchy
• GS_3DFreeMoverComponent — Standard free-locomotion mover
• Mover Context — Provides slopeDir, groundedMoveInput, and mode switching
• Grounders — Detect slope angle and trigger the switch to Slide mode
• Springs Utility — AccelerationSpringDamper and QuaternionSpringDamper used internally

Get GS_Unit

GS_Unit — Explore this gem on the product page and add it to your project.

3 - 3D Strafe Mover

The 3D Strafe Mover provides aim-relative movement where the unit strafes relative to its facing direction. This is the standard movement model for first-person and third-person shooters where the camera or aim direction determines the movement frame.

This component is not yet implemented. This page will be updated with full API reference and usage documentation when the component is available.

For usage guides and setup examples, see The Basics: GS_Unit.

See Also

• Movement – Movement subsystem overview
• 3D Free Mover – Free three-dimensional movement
• Slide Mover – Surface-sliding movement

Get GS_Unit

GS_Unit — Explore this gem on the product page and add it to your project.

4 - Side Scroller Mover

The Side Scroller Mover provides two-dimensional movement constrained to a horizontal plane with vertical jump support. This is the standard movement model for side-scrolling platformers, beat-em-ups, and other 2D gameplay projected in a 3D environment.

This component is not yet implemented. This page will be updated with full API reference and usage documentation when the component is available.

For usage guides and setup examples, see The Basics: GS_Unit.

See Also

• Movement – Movement subsystem overview
• Movers – All available mover components

Get GS_Unit

GS_Unit — Explore this gem on the product page and add it to your project.

5 - Grid Step Mover

The Grid Step Mover provides discrete, tile-based movement for units that move in fixed steps along a grid. This is the standard movement model for turn-based RPGs, tactics games, puzzle games, and any project that uses grid-locked locomotion.

This component is not yet implemented. This page will be updated with full API reference and usage documentation when the component is available.

For usage guides and setup examples, see The Basics: GS_Unit.

See Also

• Movement – Movement subsystem overview
• Movers – All available mover components

Get GS_Unit

GS_Unit — Explore this gem on the product page and add it to your project.