Case Study — Grappling Hook Mechanic

Tensio includes a fully playable Grappling Hook demo in the Tensio/Demos/GrapplingHook folder, demonstrating how to dynamically instantiate, anchor, winch, and swing from ropes during gameplay.

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Key Gameplay Concepts

1. Object Pooling: Rather than calling Instantiate per hook projectile, the demo pre-allocates a pooled RopeController GameObject and re-initializes it on demand.
2. Dynamic Pinning: Pins index 0 to the player’s weapon tip and index N to the raycast hit point on the wall or ceiling.
3. Tensile Retraction: Continuously decrements rope.SetCurrentLength() while applying directional propulsion forces to the player’s Rigidbody.
4. Natural Pendulum Motion: Setting Compliance = 0.0f creates a rigid tether, enabling physics-driven swinging without artificial spring bounce.

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Core C# Implementation Breakdown

1. Firing & Anchor Attachment

public void FireHook(RaycastHit hit)
{
    rope.gameObject.SetActive(true);

    // Position rope root at launcher muzzle
    rope.transform.position = muzzleTransform.position;

    float hitDistance = Vector3.Distance(muzzleTransform.position, hit.point);
    rope.InitSettings.Length = hitDistance;
    rope.InitializeRope();

    // Anchor Start to Player & End to Contact Point
    rope.PinParticle(0, playerTransform, muzzleTransform.position);
    rope.PinParticle(rope.ParticleCount - 1, hit.transform, hit.point);
}

2. Motorized Winch Pulling

While the player holds the grapple reel button, cable length is retracted and tensile impulse is imparted to the player body:

void UpdateGrapplePull()
{
    // Retract resting cable length
    float newLength = rope.CurrentLength - pullSpeed * Time.deltaTime;
    rope.SetCurrentLength(Mathf.Max(minGrappleLength, newLength));

    // Calculate pull vector towards anchor
    Vector3 pullDirection = (hitPoint - playerRb.position).normalized;
    float currentDistance = Vector3.Distance(playerRb.position, hitPoint);

    if (currentDistance > 1.5f)
    {
        playerRb.AddForce(pullDirection * pullForce, ForceMode.Acceleration);
    }
}

3. Detachment & Release

Releasing the grapple instantly unpins both anchors and deactivates the rope game object back into the pool:

public void ReleaseHook()
{
    rope.gameObject.SetActive(false);
}

The player preserves their exit momentum, smoothly transitioning into airborne trajectories!