Grounders

Grounders run each physics tick to determine whether the unit is in contact with the ground, what the slope looks like, and whether the surface is walkable. They write their findings to the MoverContext and switch movement modes when the ground state changes.

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

Contents

• Class Hierarchy
• GS_GrounderComponent (Base)
• Concrete Grounders
• API Reference
• Extension Guide
• See Also

Class Hierarchy

GS_GrounderComponent (base — mode-aware activation, tick management)
  └── GS_PhysicsRayGrounderComponent  (grounding mode: "Free")

GS_GrounderComponent (Base)

Tick: AzPhysics::SystemEvents::OnPostSimulateEvent (after the physics step).

Mode-Aware Activation

Listens to MoverContextNotificationBus::GroundingModeChanged. Compares the broadcast mode name against its own m_groundModeName. Calls ToggleGrounder(true/false) accordingly. The physics post-simulate handler is only registered when the grounder is active.

Per-Tick Processing

Each tick:

1. CheckCanOperate() — validates required pointers and state
2. HandleGrounding() — performs ground detection and updates MoverContext (no-op in base)

Key Fields

Concrete Grounders

API Reference

Virtual Methods

Override these when extending any grounder:

Consumed Buses

Produced Calls

Extension Guide

Use the Grounder ClassWizard template to generate a new grounder with boilerplate already in place — see GS_Unit Templates. The template offers two base class options: Physics Ray Grounder (default, includes raycast, coyote time, and gravity) or Base Grounder for fully custom detection.

Extend GS_GrounderComponent to implement custom ground detection.

#pragma once
#include <Source/Unit/Grounder/GS_GrounderComponent.h>

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

    protected:
        void Activate() override;

        void HandleGrounding() override;
        void GroundingStateChange(AZ::u32 newState) override;

    private:
        // Set in Activate():
        // m_groundModeName = "Free";
    };
}

In HandleGrounding(), run your detection and write results to the MoverContext:

void MyGrounder::HandleGrounding()
{
    AZ::Vector3 groundNormal = AZ::Vector3::CreateAxisZ();
    bool isGrounded = false;

    // ... custom detection logic ...

    GS_Unit::MoverContextRequestBus::Event(
        GetEntityId(),
        &GS_Unit::MoverContextRequestBus::Events::SetGroundNormal,
        groundNormal
    );

    AZ::u32 state = isGrounded ? 1 : 0;
    GS_Unit::MoverContextRequestBus::Event(
        GetEntityId(),
        &GS_Unit::MoverContextRequestBus::Events::SetContextState,
        "grounding", state
    );
}

See Also

• GS_PhysicsRayGrounderComponent — The standard raycast grounder
• Mover Context — Receives ground state and normal from grounders
• Movers — Consume ground state to drive physics
• Movement — Movement system overview

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