uniquake/Assets/Scripts/Support/ParticleTrailController.cs

using UnityEngine;

public class ParticleTrailController : MonoBehaviour
{
    [SerializeField]
    private ParticleSystem effect;

    [SerializeField]
    private ParticleTrail type;
    public ParticleTrail Type => type;
    
    public void Initialize(ParticleSystem effect, ParticleTrail type, int interval)
    {
        this.effect = effect;
        this.type = type;

        var main = effect.main;
        var shape = effect.shape;
        
        var emission = effect.emission;
        emission.rateOverDistance = 1.0f / interval;
        
        switch (type)
        {
            case ParticleTrail.Rocket:
            {
                main.startLifetime = new ParticleSystem.MinMaxCurve(0.6f, 1.2f);
                shape.scale = new Vector3(6f, 6f, 6f);
                
                var colorOverLifetime = effect.colorOverLifetime;
                colorOverLifetime.enabled = true;
                colorOverLifetime.color = SetupGradients(RocketColorKeys, SmokeColorKeys);
                break;
            }
            case ParticleTrail.Smoke:
            {
                main.startLifetime = new ParticleSystem.MinMaxCurve(0.2f, 0.8f);
                shape.scale = new Vector3(6f, 6f, 6f);
                
                var colorOverLifetime = effect.colorOverLifetime;
                colorOverLifetime.enabled = true;
                colorOverLifetime.color = SetupGradients(SmokeColorKeys, SmokeColorKeys2);
                break;
            }
            case ParticleTrail.Blood:
            {
                main.gravityModifierMultiplier = 0.05f;
                main.startColor = new ParticleSystem.MinMaxGradient(BloodColorMin, BloodColorMax);
                
                shape.scale = new Vector3(6f, 6f, 6f);
                break;
            }
            case ParticleTrail.Tracer:
            case ParticleTrail.Tracer2:
            {
                main.startLifetime = 0.5f;
                main.startColor = type == ParticleTrail.Tracer
                    ? new ParticleSystem.MinMaxGradient(TracerColorMin, TracerColorMax)
                    : new ParticleSystem.MinMaxGradient(Tracer2ColorMin, Tracer2ColorMax);
                
                var velocityOverLifetime = effect.velocityOverLifetime;
                velocityOverLifetime.enabled = true;
                velocityOverLifetime.space = ParticleSystemSimulationSpace.Local;
                velocityOverLifetime.x = new ParticleSystem.MinMaxCurve(-30, 30);
                velocityOverLifetime.y = new ParticleSystem.MinMaxCurve(0, 0);
                velocityOverLifetime.z = new ParticleSystem.MinMaxCurve(30, -30);
                break;
            }
            case ParticleTrail.SlightBlood:
            {
                main.gravityModifierMultiplier = 0.05f;
                main.startColor = new ParticleSystem.MinMaxGradient(BloodColorMin, BloodColorMax);
                
                shape.scale = new Vector3(6f, 6f, 6f);
                emission.rateOverDistance = 1.0f / (interval + 3);
                break;
            }
            case ParticleTrail.VoreBall:
            {
                main.startLifetime = 0.3f;
                main.startColor = new ParticleSystem.MinMaxGradient(VoreColorMin, VoreColorMax);
                
                shape.scale = new Vector3(16f, 16f, 16f);
                break;
            }
        }
    }

    public void Stop()
    {
        // Allow the current particles to finish simulation, then auto-destroy the particle effect
        var main = effect.main;
        Destroy(gameObject, main.startLifetime.constantMax);
    }

    private static ParticleSystem.MinMaxGradient SetupGradients(GradientColorKey[] minKeys, GradientColorKey[] maxKeys)
    {
        return new ParticleSystem.MinMaxGradient
        {
            mode = ParticleSystemGradientMode.TwoGradients,
            gradientMin = new Gradient { mode = GradientMode.Fixed, colorKeys = minKeys },
            gradientMax = new Gradient { mode = GradientMode.Fixed, colorKeys = maxKeys },
        };
    }

    // TODO: these colors ought to be initialized from the Quake palette instead of being hard-coded.
    // That will allow them to work with custom palettes from total conversions.
    private static readonly GradientColorKey[] RocketColorKeys = 
    {
        new GradientColorKey(new Color32(223, 171, 39, 255), 0.167f),
        new GradientColorKey(new Color32(191, 119, 47, 255), 0.333f),
        new GradientColorKey(new Color32(91, 91, 91, 255), 0.5f),
        new GradientColorKey(new Color32(75, 75, 75, 255), 0.667f),
        new GradientColorKey(new Color32(63, 63, 63, 255), 0.833f),
        new GradientColorKey(new Color32(47, 47, 47, 255), 1.0f),
    };

    private static readonly GradientColorKey[] SmokeColorKeys = 
    {
        new GradientColorKey(new Color32(91, 91, 91, 255), 0.25f),
        new GradientColorKey(new Color32(75, 75, 75, 255), 0.5f),
        new GradientColorKey(new Color32(63, 63, 63, 255), 0.75f),
        new GradientColorKey(new Color32(47, 47, 47, 255), 1.0f),
    };

    private static readonly GradientColorKey[] SmokeColorKeys2 = 
    {
        new GradientColorKey(new Color32(63, 63, 63, 255), 0.5f),
        new GradientColorKey(new Color32(47, 47, 47, 255), 1.0f),
    };

    private static readonly Color BloodColorMin = new Color32(31, 0, 0, 255);
    private static readonly Color BloodColorMax = new Color32(55, 0, 0, 255);

    private static readonly Color TracerColorMin = new Color32(27, 27, 0, 255);
    private static readonly Color TracerColorMax = new Color32(83, 83, 11, 255);

    private static readonly Color Tracer2ColorMin = new Color32(147, 31, 7, 255);
    private static readonly Color Tracer2ColorMax = new Color32(239, 191, 119, 255);

    private static readonly Color VoreColorMin = new Color32(95, 51, 63, 255);
    private static readonly Color VoreColorMax = new Color32(59, 31, 35, 255);
}