How To Make Parallax Background Infinite Scrolling Unity

Dianna Russini

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Apr 02, 2025

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How To Make Parallax Background Infinite Scrolling in Unity

Creating an infinite scrolling parallax background in Unity adds a captivating layer of depth and immersion to your 2D or 2.5D games. This tutorial will guide you through the process, focusing on efficient techniques for optimal performance. We'll cover implementing parallax scrolling, achieving the infinite loop, and optimizing for smooth gameplay.

Understanding Parallax Scrolling

Parallax scrolling simulates depth by moving background elements at different speeds. Closer objects move faster, while distant objects move slower, creating the illusion of 3D space within a 2D environment. This technique significantly enhances the visual appeal of your game.

Key Components:

• Multiple Background Layers: You'll need at least two layers, but more create a richer effect. Each layer represents a different depth plane.
• Different Scroll Speeds: Each layer scrolls at a speed inversely proportional to its perceived distance. The closest layer scrolls the fastest, the furthest the slowest.
• Looping Mechanism: To achieve the "infinite" effect, you need a mechanism to seamlessly loop the background image when it scrolls off-screen.

Implementing the Infinite Parallax Scrolling in Unity

Let's break down the steps to create your infinite scrolling parallax background in Unity:

1. Setting Up the Scene:

• Create Background Layers: Import your background images into Unity. Create separate GameObjects for each layer. Name them clearly (e.g., "BackgroundLayerFar," "BackgroundLayerMid," "BackgroundLayerNear").
• Add Sprite Renderers: Add a Sprite Renderer component to each GameObject. Assign the corresponding background image to each renderer.
• Adjust Sorting Layers: Ensure the layers are ordered correctly in the Sorting Layers settings to prevent visual artifacts (closest layer has the highest order).

2. Scripting the Parallax Effect:

Create a new C# script (e.g., ParallaxBackground.cs). We'll use this script to manage the scrolling behavior. Here's a sample script:

using UnityEngine;

public class ParallaxBackground : MonoBehaviour
{
    public Transform cameraTransform;
    public float parallaxStrength = 0.5f; // Adjust this value to control the parallax effect intensity
    public float backgroundWidth;

    private float previousCameraX;

    void Start()
    {
        previousCameraX = cameraTransform.position.x;
        backgroundWidth = GetComponent().sprite.bounds.size.x;
    }

    void LateUpdate()
    {
        float deltaX = cameraTransform.position.x - previousCameraX;
        transform.position += Vector3.right * (deltaX * parallaxStrength);

        //Infinite Scrolling Implementation
        if (transform.position.x < -backgroundWidth)
        {
            transform.position += Vector3.right * (backgroundWidth * 2);
        }
        else if (transform.position.x > backgroundWidth)
        {
            transform.position -= Vector3.right * (backgroundWidth * 2);
        }
        previousCameraX = cameraTransform.position.x;
    }
}

3. Attaching the Script and Configuring Parameters:

• Attach the script: Attach the ParallaxBackground script to each background layer GameObject.
• Assign Camera: In the Inspector, assign your main camera's transform to the cameraTransform field for each layer.
• Adjust parallaxStrength: Experiment with the parallaxStrength value to fine-tune the scrolling speed for each layer. Smaller values create a subtle effect; larger values create a more pronounced parallax.
• Determine backgroundWidth: The script currently calculates backgroundWidth dynamically using the sprite bounds. However, in some cases, this method might not be accurate. For improved control, consider manually entering the exact width of your background sprites, which might be necessary for perfectly seamless transitions.

4. Optimizing for Performance:

• Lower Resolution Images: Use optimized background images with lower resolutions to reduce memory usage and improve performance.
• Pooling: For complex backgrounds, consider object pooling to recycle and reuse background segments, rather than constantly instantiating new ones.
• Culling: Implement camera culling to prevent rendering of background segments outside the camera's view frustum, which can further improve performance.

Advanced Techniques

• Multiple directions: Extend this technique for vertical parallax scrolling or even diagonal scrolling. Simply adjust the vector used in the transform.position += line.
• Non-linear parallax: Use curves to create more visually interesting parallax effects.

By following these steps and employing optimization strategies, you can successfully create visually stunning and performant infinite parallax scrolling backgrounds in your Unity projects, significantly enhancing the user experience. Remember to experiment and adjust parameters to achieve the desired effect for your specific game.