Color and size over lifetime in Unity

Introduction

Changing color and size over lifetime helps make effects look alive and natural. It adds smooth changes as things grow or fade.

When making a fire particle that changes from bright yellow to dark smoke

When creating a magic spell that grows bigger and changes color as it fades

When animating a bubble that grows and becomes transparent before popping

When designing rain drops that shrink and disappear as they fall

Syntax

Unity

ParticleSystem.MainModule main = particleSystem.main;
main.startColor = new ParticleSystem.MinMaxGradient(Color.white, Color.red);
main.startSize = new ParticleSystem.MinMaxCurve(1f, 3f);

ParticleSystem.ColorOverLifetimeModule colorOverLifetime = particleSystem.colorOverLifetime;
colorOverLifetime.enabled = true;
colorOverLifetime.color = new ParticleSystem.MinMaxGradient(
    new Gradient() {
        colorKeys = new GradientColorKey[] {
            new GradientColorKey(Color.white, 0f),
            new GradientColorKey(Color.red, 1f)
        },
        alphaKeys = new GradientAlphaKey[] {
            new GradientAlphaKey(1f, 0f),
            new GradientAlphaKey(0f, 1f)
        }
    }
);

ParticleSystem.SizeOverLifetimeModule sizeOverLifetime = particleSystem.sizeOverLifetime;
sizeOverLifetime.enabled = true;
sizeOverLifetime.size = new ParticleSystem.MinMaxCurve(1f, AnimationCurve.Linear(0f, 1f, 1f, 0f));

Use colorOverLifetime.enabled = true to activate color changes over time.

Gradients define how color and transparency change from start (0) to end (1) of particle life.

Examples

This sets all particles to stay red during their lifetime.

Unity

var colorOverLifetime = particleSystem.colorOverLifetime;
colorOverLifetime.enabled = true;
colorOverLifetime.color = Color.red;

This makes particles grow from half size to double size over their life.

Unity

var sizeOverLifetime = particleSystem.sizeOverLifetime;
sizeOverLifetime.enabled = true;
sizeOverLifetime.size = AnimationCurve.Linear(0f, 0.5f, 1f, 2f);

This smoothly changes particle color from yellow to black and fades out transparency.

Unity

Gradient gradient = new Gradient();
gradient.colorKeys = new GradientColorKey[] {
    new GradientColorKey(Color.yellow, 0f),
    new GradientColorKey(Color.black, 1f)
};
gradient.alphaKeys = new GradientAlphaKey[] {
    new GradientAlphaKey(1f, 0f),
    new GradientAlphaKey(0f, 1f)
};

var colorOverLifetime = particleSystem.colorOverLifetime;
colorOverLifetime.enabled = true;
colorOverLifetime.color = new ParticleSystem.MinMaxGradient(gradient);

Sample Program

This script changes particles from white to blue and shrinks them to zero size as they live.

Unity

using UnityEngine;

public class ColorSizeOverLifetime : MonoBehaviour
{
    public ParticleSystem particleSystem;

    void Start()
    {
        var main = particleSystem.main;
        main.startColor = Color.white;
        main.startSize = 1f;

        var colorOverLifetime = particleSystem.colorOverLifetime;
        colorOverLifetime.enabled = true;

        Gradient gradient = new Gradient();
        gradient.colorKeys = new GradientColorKey[] {
            new GradientColorKey(Color.white, 0f),
            new GradientColorKey(Color.blue, 1f)
        };
        gradient.alphaKeys = new GradientAlphaKey[] {
            new GradientAlphaKey(1f, 0f),
            new GradientAlphaKey(0f, 1f)
        };

        colorOverLifetime.color = new ParticleSystem.MinMaxGradient(gradient);

        var sizeOverLifetime = particleSystem.sizeOverLifetime;
        sizeOverLifetime.enabled = true;
        sizeOverLifetime.size = new ParticleSystem.MinMaxCurve(1f, AnimationCurve.Linear(0f, 1f, 1f, 0f));
    }
}

Important Notes

Always enable the colorOverLifetime and sizeOverLifetime modules to see changes.

Use gradients to control smooth color and transparency changes.

Animation curves let you customize size changes over time easily.

Summary

Color and size over lifetime make particles look natural and dynamic.

Enable and set gradients or curves to control these changes.

Use this to create effects like fading, growing, or color shifting.

Practice

1. What does the ColorOverLifetime module do in Unity's Particle System?

easy

A. It adjusts the size of particles instantly.

B. It changes the color of particles smoothly as they age.

C. It controls the speed of particles over time.

D. It sets the initial color of particles only.

Solution

1. Step 1: Understand the purpose of ColorOverLifetime

   The ColorOverLifetime module is designed to modify particle colors gradually as they live.

2. Step 2: Compare options with module function

   Only It changes the color of particles smoothly as they age. correctly describes this smooth color change over particle lifetime.

3. Final Answer:

   It changes the color of particles smoothly as they age. -> Option B

4. Quick Check:

   ColorOverLifetime = Smooth color change [OK]

Hint: ColorOverLifetime changes colors gradually over particle life [OK]

Common Mistakes:

• Confusing ColorOverLifetime with initial color setting
• Thinking it controls size or speed
• Assuming it changes color instantly

2. Which of the following is the correct way to enable the SizeOverLifetime module in a Unity Particle System script?

easy

A. particleSystem.sizeoverlifetime.enabled = true;

B. particleSystem.SizeOverLifetime.enabled = true;

C. particleSystem.sizeOverLifetime.enabled = true;

D. particleSystem.sizeOverLifetime.enable = true;

Solution

1. Step 1: Check correct property casing and spelling

   Unity uses camelCase for properties, so sizeOverLifetime is correct.

2. Step 2: Verify property names and boolean flags

   The property to enable is enabled, not enable.

3. Final Answer:

   particleSystem.sizeOverLifetime.enabled = true; -> Option C

4. Quick Check:

   Correct casing and property name = particleSystem.sizeOverLifetime.enabled = true; [OK]

Hint: Use camelCase and 'enabled' property to activate modules [OK]

Common Mistakes:

• Incorrect capitalization of 'sizeOverLifetime'
• Using 'enable' instead of 'enabled'
• Misspelling the module name

3. Given this code snippet in Unity:

var ps = GetComponent<ParticleSystem>();
var col = ps.colorOverLifetime;
col.enabled = true;
col.color = new ParticleSystem.MinMaxGradient(Color.red, Color.blue);

What will happen to the particles' colors over their lifetime?

medium

A. Particles will smoothly change color from red to blue as they age.

B. Particles will stay red throughout their life.

C. Particles will instantly switch from red to blue at half their lifetime.

D. Particles will not change color because the gradient is invalid.

Solution

1. Step 1: Analyze the colorOverLifetime setup

   The code enables colorOverLifetime and sets a gradient from red to blue.

2. Step 2: Understand gradient effect on particles

   This gradient causes particles to smoothly transition from red at birth to blue at death.

3. Final Answer:

   Particles will smoothly change color from red to blue as they age. -> Option A

4. Quick Check:

   Gradient red to blue = smooth color change [OK]

Hint: Gradient from color A to B means smooth transition over lifetime [OK]

Common Mistakes:

• Assuming color stays constant
• Thinking color changes instantly
• Believing gradient is invalid without alpha

4. Identify the error in this Unity C# code for SizeOverLifetime:

var ps = GetComponent<ParticleSystem>();
var size = ps.sizeOverLifetime;
size.enabled = true;
size.size = new ParticleSystem.MinMaxCurve(1.0f, 0.0f);

medium

A. MinMaxCurve cannot have start value greater than end value.

B. The size curve should be assigned using a curve, not MinMaxCurve.

C. The MinMaxCurve constructor parameters are reversed; it should be (0.0f, 1.0f).

D. There is no error; the code shrinks particles from size 1 to 0 correctly.

Solution

1. Step 1: Review MinMaxCurve usage for size

   MinMaxCurve can define a linear change from start to end size; start larger than end is valid.

2. Step 2: Confirm code logic

   The code enables sizeOverLifetime and sets size to shrink from 1.0 to 0.0, which is correct.

3. Final Answer:

   There is no error; the code shrinks particles from size 1 to 0 correctly. -> Option D

4. Quick Check:

   Shrinking size from 1 to 0 is valid [OK]

Hint: Start size can be bigger than end size for shrinking effect [OK]

Common Mistakes:

• Thinking start value must be less than end value
• Confusing MinMaxCurve with animation curve
• Assuming reversed parameters cause error

5. You want particles to start fully transparent, become fully visible halfway through their life, then fade out again by the end. How can you set this using ColorOverLifetime in Unity?

hard

A. Use a gradient with alpha keys at 0 (0), 0.5 (1), and 1 (0) to control transparency over lifetime.

B. Set the start color alpha to 0 and end color alpha to 1 in ColorOverLifetime gradient.

C. Enable SizeOverLifetime and animate size from 0 to 1 to 0 to control visibility.

D. Use a single color with alpha 1 and animate particle emission rate.

Solution

1. Step 1: Understand alpha control with ColorOverLifetime

   Alpha keys in gradient let you control transparency at different life points.

2. Step 2: Set gradient alpha keys for fade in and fade out

   Alpha 0 at start, 1 at half life, and 0 at end creates the desired transparency effect.

3. Final Answer:

   Use a gradient with alpha keys at 0 (0), 0.5 (1), and 1 (0) to control transparency over lifetime. -> Option A

4. Quick Check:

   Alpha keys control transparency fade in/out [OK]

Hint: Use alpha keys in gradient for fade in and fade out [OK]

Common Mistakes:

• Only setting start and end alpha without middle key
• Using size to control transparency
• Changing emission rate instead of color alpha