ParticleSystem.SetCustomParticleData

Parameters

Description

Set a stream of custom per-particle data.

Note that if you enable the Custom Data module, it writes into the particle data buffer during the Particle System update. If you want to provide your own data using this function, disable the Custom Data module.

However, if you want to modify the data that the Custom Data module generates: 1. Use ParticleSystem.GetCustomParticleData to get the particle data. 2. Modify the particle data. 3. Use SetCustomParticleData to apply the modified particle data back to the Custom Data module.

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

[RequireComponent(typeof(ParticleSystem))]
public class ExampleClass : MonoBehaviour {

    private ParticleSystem ps;
    private ParticleSystemRenderer psr;
    private List<Vector4> customData = new List<Vector4>();
    public float minDist = 30.0f;

    void Start() {

        ps = GetComponent<ParticleSystem>();
        psr = GetComponent<ParticleSystemRenderer>();

        // emit in a sphere with no speed
        var main = ps.main;
        main.startSpeedMultiplier = 0.0f;
        main.simulationSpace = ParticleSystemSimulationSpace.World; // so our particle positions don't require any extra transformation, to compare with the mouse position
        var emission = ps.emission;
        emission.rateOverTimeMultiplier = 200.0f;
        var shape = ps.shape;
        shape.shapeType = ParticleSystemShapeType.Sphere;
        shape.radius = 4.0f;
        psr.sortMode = ParticleSystemSortMode.YoungestInFront;

        // send custom data to the shader
        psr.EnableVertexStreams(ParticleSystemVertexStreams.Custom1);
    }

    void Update() {

        Camera mainCam = Camera.main;

        ps.GetCustomParticleData(customData, ParticleSystemCustomData.Custom1);

        int particleCount = ps.particleCount;
        ParticleSystem.Particle[] particles = new ParticleSystem.Particle[particleCount];
        ps.GetParticles(particles);

        for (int i = 0; i < particles.Length; i++)
        {
            Vector3 sPos = mainCam.WorldToScreenPoint(particles[i].position + ps.transform.position);

            // set custom data to 1, if close enough to the mouse
            if (Vector2.Distance(sPos, Input.mousePosition) < minDist)
            {
                customData[i] = new Vector4(1, 0, 0, 0);
            }
            // otherwise, fade the custom data back to 0
            else
            {
                float particleLife = particles[i].remainingLifetime / ps.main.startLifetimeMultiplier;

                if (customData[i].x > 0)
                {
                    float x = customData[i].x;
                    x = Mathf.Max(x - Time.deltaTime, 0.0f);
                    customData[i] = new Vector4(x, 0, 0, 0);
                }
            }
        }

        ps.SetCustomParticleData(customData, ParticleSystemCustomData.Custom1);
    }

    void OnGUI() {

        minDist = GUI.HorizontalSlider(new Rect(25, 40, 100, 30), minDist, 0.0f, 100.0f);
    }
}

Here is an example of a custom shader that can be used with the above script:

          Shader "Particles/CustomVertexStream" {
Properties {
    _TintColor ("Tint Color", Color) = (0.5,0.5,0.5,0.5)
    _MainTex ("Particle Texture", 2D) = "white" {}
    _OffsetValue("Offset Value", Range(0,1)) = 0.4
}

Category {
    Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" }
    Blend SrcAlpha OneMinusSrcAlpha
    ColorMask RGB
    Cull Off Lighting Off ZWrite Off

    SubShader {
        Pass {

            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile_particles
            #pragma multi_compile_fog

            #include "UnityCG.cginc"

            sampler2D _MainTex;
            fixed4 _TintColor;
            float _OffsetValue;

            struct appdata_t {
                float4 vertex : POSITION;
                float3 normal : NORMAL;
                fixed4 color : COLOR;
                float2 texcoord : TEXCOORD0;
                float4 customData : TEXCOORD1;
            };

            struct v2f {
                float4 vertex : SV_POSITION;
                fixed4 color : COLOR;
                float2 texcoord : TEXCOORD0;
                float4 customData : TEXCOORD1;
                UNITY_FOG_COORDS(2)
            };

            float4 _MainTex_ST;

            v2f vert (appdata_t v)
            {
                v.vertex.y = lerp(v.vertex.y, v.vertex.y + _OffsetValue, v.customData.x);

                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);

                float4 offsetX = float4(-1, 1, 1, -1);
                float4 offsetY = float4(1, 1, -1, -1);

                o.color = v.color;
                o.texcoord = TRANSFORM_TEX(v.texcoord,_MainTex);
                o.customData = v.customData;
                UNITY_TRANSFER_FOG(o,o.vertex);

                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 col = 2.0f * i.color * _TintColor * tex2D(_MainTex, i.texcoord);
                fixed4 col2 = fixed4(i.customData.x, i.customData.y, i.customData.z, col.a);
                fixed4 final = lerp(col, col*col2, i.customData.x);

                UNITY_APPLY_FOG(i.fogCoord, final);
                return final;
            }
            ENDCG
        }
    }
}
}

Here is an example of a script that assigns a unique ID to each particle when it is born:

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

[RequireComponent(typeof(ParticleSystem))]
public class ExampleClass : MonoBehaviour {

    private ParticleSystem ps;
    private List<Vector4> customData = new List<Vector4>();
    private int uniqueID;

    void Start() {

        ps = GetComponent<ParticleSystem>();
    }

    void Update() {

        ps.GetCustomParticleData(customData, ParticleSystemCustomData.Custom1);

        for (int i = 0; i < customData.Count; i++)
        {
            // set custom data to the next ID, if it is in the default 0 state
            if (customData[i].x == 0.0f)
            {
                customData[i] = new Vector4(++uniqueID, 0, 0, 0);
            }
        }

        ps.SetCustomParticleData(customData, ParticleSystemCustomData.Custom1);
    }
}