micromissiles-unity/Assets/Scripts/Missile.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Missile : Agent {
  [SerializeField]
  protected bool _showDebugVectors = true;

  [SerializeField]
  private Vector3 _boostAcceleration;
  // Return whether a target can be assigned to the missile.
  public override bool IsAssignable() {
    bool assignable = !HasLaunched() && !HasAssignedTarget();
    return assignable;
  }

  // Assign the given target to the missile.
  public override void AssignTarget(Agent target) {
    base.AssignTarget(target);
  }

  // Unassign the target from the missile.
  public override void UnassignTarget() {
    base.UnassignTarget();
  }  

  protected override void UpdateReady(double deltaTime) {
    Vector3 accelerationInput = Vector3.zero;
    Vector3 acceleration = CalculateAcceleration(accelerationInput);
    // GetComponent<Rigidbody>().AddForce(acceleration, ForceMode.Acceleration);
  }

  protected override void FixedUpdate() {
    base.FixedUpdate();
    if (_showDebugVectors) {
      DrawDebugVectors();
    }
  }

  protected override void UpdateBoost(double deltaTime) {
    // The missile only accelerates along its roll axis (forward in Unity)
    Vector3 rollAxis = transform.forward;

    // Calculate boost acceleration
    float boostAcceleration =
        (float)(_staticConfig.boostConfig.boostAcceleration * Constants.kGravity);
    Vector3 accelerationInput = boostAcceleration * rollAxis;

    // Calculate the total acceleration
    Vector3 acceleration = CalculateAcceleration(accelerationInput);

    // Apply the acceleration force
    GetComponent<Rigidbody>().AddForce(acceleration, ForceMode.Acceleration);
    _boostAcceleration = acceleration;
  }
  protected override void UpdateMidCourse(double deltaTime) {}

  protected Vector3 CalculateAcceleration(Vector3 accelerationInput,
                                          bool compensateForGravity = false) {
    Vector3 gravity = Physics.gravity;
    if (compensateForGravity) {
      Vector3 gravityProjection = CalculateGravityProjectionOnPitchAndYaw();
      accelerationInput -= gravityProjection;
    }

    float airDrag = CalculateDrag();
    float liftInducedDrag = CalculateLiftInducedDrag(accelerationInput);
    float dragAcceleration = -(airDrag + liftInducedDrag);

    // Project the drag acceleration onto the forward direction
    Vector3 dragAccelerationAlongRoll = dragAcceleration * transform.forward;

    return accelerationInput + gravity + dragAccelerationAlongRoll;
  }

  private void OnTriggerEnter(Collider other) {
    if (other.gameObject.name == "Floor") {
      this.MarkAsMiss();
    }
    // Check if the collision is with another Agent
    Agent otherAgent = other.gameObject.GetComponentInParent<Agent>();
    if (otherAgent != null && otherAgent.GetComponent<Target>() != null) {
      // Check kill probability before marking as hit
      float killProbability = _staticConfig.hitConfig.killProbability;
      GameObject markerObject = Instantiate(Resources.Load<GameObject>("Prefabs/HitMarkerPrefab"),
                                            transform.position, Quaternion.identity);
      if (Random.value <= killProbability) {
        // Set green for hit
        markerObject.GetComponent<Renderer>().material.color = new Color(0, 1, 0, 0.15f);
        // Mark both this agent and the other agent as hit
        this.MarkAsHit();
        otherAgent.MarkAsHit();

      } else {
        // Set red for miss
        markerObject.GetComponent<Renderer>().material.color = new Color(1, 0, 0, 0.15f);
        this.MarkAsMiss();
        // otherAgent.MarkAsMiss();
      }
    }
  }

  protected float CalculateMaxAcceleration() {
    float maxReferenceAcceleration =
        (float)(_staticConfig.accelerationConfig.maxReferenceAcceleration * Constants.kGravity);
    float referenceSpeed = _staticConfig.accelerationConfig.referenceSpeed;
    return Mathf.Pow(GetComponent<Rigidbody>().velocity.magnitude / referenceSpeed, 2) *
           maxReferenceAcceleration;
  }
  protected Vector3 CalculateGravityProjectionOnPitchAndYaw() {
    Vector3 gravity = Physics.gravity;
    Vector3 pitchAxis = transform.right;
    Vector3 yawAxis = transform.up;

    // Project the gravity onto the pitch and yaw axes
    float gravityProjectionPitchCoefficient = Vector3.Dot(gravity, pitchAxis);
    float gravityProjectionYawCoefficient = Vector3.Dot(gravity, yawAxis);

    // Return the sum of the projections
    return gravityProjectionPitchCoefficient * pitchAxis +
           gravityProjectionYawCoefficient * yawAxis;
  }

  private float CalculateDrag() {
    float dragCoefficient = _staticConfig.liftDragConfig.dragCoefficient;
    float crossSectionalArea = _staticConfig.bodyConfig.crossSectionalArea;
    float mass = _staticConfig.bodyConfig.mass;
    float dynamicPressure = (float)GetDynamicPressure();
    float dragForce = dragCoefficient * dynamicPressure * crossSectionalArea;
    return dragForce / mass;
  }

  private float CalculateLiftInducedDrag(Vector3 accelerationInput) {
    float liftAcceleration =
        (accelerationInput - Vector3.Dot(accelerationInput, transform.up) * transform.up).magnitude;
    float liftDragRatio = _staticConfig.liftDragConfig.liftDragRatio;
    return Mathf.Abs(liftAcceleration / liftDragRatio);
  }

  protected virtual void DrawDebugVectors() {
    if (_target != null) {
      // Line of sight
      Debug.DrawLine(transform.position, _target.transform.position, new Color(1, 1, 1, 0.15f));

      // Velocity vector
      Debug.DrawRay(transform.position, GetVelocity() * 0.01f, new Color(0, 0, 1, 0.15f));

      // Current forward direction
      Debug.DrawRay(transform.position, transform.forward * 5f, Color.yellow);

      // Pitch axis (right)
      Debug.DrawRay(transform.position, transform.right * 5f, Color.red);

      // Yaw axis (up)
      Debug.DrawRay(transform.position, transform.up * 5f, Color.magenta);
    }
  }
}