Clear Pixi.js Graphics Instance for Redrawing

In Pixi.js, managing and updating visual shapes dynamically is a common requirement for interactive applications and games. This article provides a straightforward guide on how to clear previously drawn shapes from a PIXI.Graphics instance and redraw new ones using the built-in clear() method, ensuring optimal rendering performance without leaking memory.

To remove previously drawn shapes from a Graphics object in Pixi.js, you must call the clear() method on that specific instance. This method resets the graphics buffer, erasing all paths, fills, and strokes associated with the object, allowing you to define new geometry immediately afterward.

Code Example

Here is a basic implementation demonstrating how to draw a shape, clear it, and then redraw a new shape on the same Graphics instance:

import * as PIXI from 'pixi.js';

// 1. Create the Pixi.js Application and Graphics instance
const app = new PIXI.Application({ width: 800, height: 600 });
document.body.appendChild(app.view);

const graphics = new PIXI.Graphics();
app.stage.addChild(graphics);

// 2. Draw an initial shape (a red rectangle)
graphics.beginFill(0xFF0000);
graphics.drawRect(50, 50, 100, 100);
graphics.endFill();

// 3. Clear the graphics instance to remove the red rectangle
graphics.clear();

// 4. Redraw a new shape (a blue circle) on the same instance
graphics.beginFill(0x0000FF);
graphics.drawCircle(200, 200, 50);
graphics.endFill();

Why Use clear() Instead of Creating New Instances?

Reusing a single PIXI.Graphics instance by calling clear() is significantly more efficient than destroying the old instance and instantiating a new one. Creating new objects frequently triggers garbage collection, which can cause noticeable stuttering or frame drops in web browsers.

Best Practices for Dynamic Redrawing

When updating shapes inside a game loop or an animation ticker, always call clear() at the beginning of the update step before applying the new drawing commands.

app.ticker.add(() => {
    // Clear the canvas of previous frame's drawings
    graphics.clear();
    
    // Draw the updated frame content
    graphics.beginFill(0x00FF00);
    graphics.drawCircle(character.x, character.y, 20);
    graphics.endFill();
});

By maintaining a single Graphics reference and utilizing clear(), you keep the GPU memory clean and ensure smooth rendering transitions.