physics

[PhysX] Balancing Kinetic Impact with Mass and Velocity

Solution

physicsrigidbodykinematicsmovement

Unity 2021.x - Unity 6.3.x

Published Sun, May 10

Reviewed by _architect

Chief Editor

80 posts

Issue

The challenge involves balancing multiple game objects with distinct mass and speed attributes to ensure that high-velocity entities and heavy-weight entities maintain comparable kinetic impact while reflecting defensive vulnerabilities.
Improperly configured mass ratios often lead to physics instability or unfair gameplay advantages for specific unit types.

Consistent impact is achieved by establishing an inverse trade-off curve where mass multiplied by velocity remains constant across different types.

Explanation

To achieve balanced gameplay across varied object types, a trade-off curve between mass and speed must be established.

This approach ensures that while each object type feels distinct, their overall impact remains fair within the game mechanics. A constant momentum target allows you to mathematically derive attributes for new entities.

Define a target momentum or kinetic energy constant for your object.
Calculate the required mass using the formula: mass = Constant / Velocity.
Apply the calculated mass to the Rigidbody component in the Inspector.
Scale the drag and angularDrag values inversely to the mass to maintain consistent deceleration across types.

Additional Tips

Enable ContinuousDynamic collision detection on high-speed, low mass objects to prevent physics tunneling through geometry.
Use ForceMode.Impulse for instantaneous velocity changes to ensure the mass correctly influences the resulting motion.
Utilize an AnimationCurve to visually map the mass-to-speed ratio for easier tuning and visual debugging within the Editor.

Copy


using UnityEngine;

[RequireComponent(typeof(Rigidbody))]
public class PhysicsImpactBalancer : MonoBehaviour
{
    [Header("Balancing Settings")]
    [SerializeField] private float impactConstant = 50f;
    [SerializeField] private float desiredTopSpeed = 10f;

    private Rigidbody rb;

    void Awake()
    {
        rb = GetComponent<Rigidbody>();
        ApplyBalancedPhysics();
    }

    [ContextMenu("Apply Balanced Physics")]
    public void ApplyBalancedPhysics()
    {
        // Ensure Rigidbody exists and desiredSpeed is not zero
        if (rb == null) rb = GetComponent<Rigidbody>();
        if (desiredTopSpeed <= 0) return;

        // mass = constant / velocity to maintain momentum parity
        rb.mass = impactConstant / desiredTopSpeed;
    }
}

Related Posts Haven't quite found a solution to your problem? We think these posts might help you.

[Collider Configuration] Flawless Dual Setup for Blocking & Triggers [Key Press] Stop Input.GetKeyDown Double Triggers [Particle System] Particles Detach from Moving GameObjects

Content inspired by a Unity discussion post.

UNITYREF

Your Pit Stop For Solving ANYTHING in Unity

[PhysX] Balancing Kinetic Impact with Mass and Velocity