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Amitkapadi/ParticleFollow.cs

Forked from firebellys/ParticleFollow.cs
Created June 28, 2022 04:07
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  1. @firebellys firebellys revised this gist Dec 23, 2016. No changes.
  2. @firebellys firebellys created this gist Dec 23, 2016.
    88 changes: 88 additions & 0 deletions ParticleFollow.cs
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    Original file line number Diff line number Diff line change
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    // A lifetime based particle attractor for Unity
    // July 23, 2016
    // CaranElmoth
    // http://www.oldschoolpixels.com/?p=669


    using UnityEngine;

    public class ParticleAttractorBhv : MonoBehaviour
    {
    // The particle system to operate on
    public ParticleSystem AffectedParticles = null;

    // Normalized treshold on the particle lifetime
    // 0: affect particles right after they are born
    // 1: never affect particles
    [Range(0.0f, 1.0f)]
    public float ActivationTreshold = 1.0f;

    // Transform cache
    private Transform m_rTransform = null;
    // Array to store particles info
    private ParticleSystem.Particle[] m_rParticlesArray = null;
    // Is this particle system simulating in world space?
    private bool m_bWorldPosition = false;
    // Multiplier to normalize movement cursor after treshold is crossed
    private float m_fCursorMultiplier = 1.0f;

    void Awake()
    {
    // Let's cache the transform
    m_rTransform = this.transform;
    // Setup particle system info
    Setup();
    }

    // To store how many particles are active on each frame
    private int m_iNumActiveParticles = 0;
    // The attractor target
    private Vector3 m_vParticlesTarget = Vector3.zero;
    // A cursor for the movement interpolation
    private float m_fCursor = 0.0f;
    void LateUpdate()
    {
    // Work only if we have something to work on :)
    if(AffectedParticles != null)
    {
    // Let's fetch active particles info
    m_iNumActiveParticles = AffectedParticles.GetParticles(m_rParticlesArray);
    // The attractor's target is it's world space position
    m_vParticlesTarget = m_rTransform.position;
    // If the system is not simulating in world space, let's project the attractor's target in the system's local space
    if (!m_bWorldPosition)
    m_vParticlesTarget -= AffectedParticles.transform.position;

    // For each active particle...
    for(int iParticle = 0; iParticle < m_iNumActiveParticles; iParticle++) { // The movement cursor is the opposite of the normalized particle's lifetime m_fCursor = 1.0f - (m_rParticlesArray[iParticle].lifetime / m_rParticlesArray[iParticle].startLifetime); // Are we over the activation treshold? if (m_fCursor >= ActivationTreshold)
    {
    // Let's project the overall cursor in the "over treshold" normalized space
    m_fCursor -= ActivationTreshold;
    m_fCursor *= m_fCursorMultiplier;

    // Take over the particle system imposed velocity
    m_rParticlesArray[iParticle].velocity = Vector3.zero;
    // Interpolate the movement towards the target with a nice quadratic easing
    m_rParticlesArray[iParticle].position = Vector3.Lerp(m_rParticlesArray[iParticle].position, m_vParticlesTarget, m_fCursor * m_fCursor);
    }
    }

    // Let's update the active particles
    AffectedParticles.SetParticles(m_rParticlesArray, m_iNumActiveParticles);
    }
    }

    public void Setup()
    {
    // If we have a system to setup...
    if (AffectedParticles != null)
    {
    // Prepare enough space to store particles info
    m_rParticlesArray = new ParticleSystem.Particle[AffectedParticles.maxParticles];
    // Is the particle system working in world space? Let's store this info
    m_bWorldPosition = AffectedParticles.simulationSpace == ParticleSystemSimulationSpace.World;
    // This the ratio of the total lifetime cursor to the "over treshold" section
    m_fCursorMultiplier = 1.0f / (1.0f - ActivationTreshold);
    }
    }
    }