Source: motion-blur/src/MotionBlurFilter.ts

import { vertex } from '@tools/fragments';
import fragment from './motion-blur.frag';
import { Filter, ObservablePoint, Point } from '@pixi/core';
import type { IPoint, CLEAR_MODES, FilterSystem, RenderTexture } from '@pixi/core';

/**
 * The MotionBlurFilter applies a Motion blur to an object.<br>
 * ![original](../tools/screenshots/dist/original.png)![filter](../tools/screenshots/dist/motion-blur.png)
 *
 * @class
 * @extends PIXI.Filter
 * @see @pixi/filter-motion-blur
 * @see pixi-filters
 */
class MotionBlurFilter extends Filter
{
    /**
     * The kernelSize of the blur, higher values are slower but look better.
     * Use odd value greater than 5.
     */
    public kernelSize = 5;

    private _velocity: IPoint;

    /**
     * @param {PIXI.ObservablePoint|PIXI.Point|number[]} [velocity=[0, 0]] - Sets the velocity of the motion for blur effect.
     * @param {number} [kernelSize=5] - The kernelSize of the blur filter. Must be odd number >= 5
     * @param {number} [offset=0] - The offset of the blur filter.
     */
    constructor(velocity: number[] | Point | ObservablePoint = [0, 0], kernelSize = 5, offset = 0)
    {
        super(vertex, fragment);
        this.uniforms.uVelocity = new Float32Array(2);
        this._velocity = new ObservablePoint(this.velocityChanged, this);
        this.setVelocity(velocity);

        this.kernelSize = kernelSize;
        this.offset = offset;
    }

    /**
     * Override existing apply method in PIXI.Filter
     * @private
     */
    apply(filterManager: FilterSystem, input: RenderTexture, output: RenderTexture, clear: CLEAR_MODES): void
    {
        const { x, y } = this.velocity;

        this.uniforms.uKernelSize = (x !== 0 || y !== 0) ? this.kernelSize : 0;
        filterManager.applyFilter(this, input, output, clear);
    }

    /**
     * Sets the velocity of the motion for blur effect.
     *
     * @member {PIXI.ObservablePoint|PIXI.Point|number[]}
     */
    set velocity(value: IPoint)
    {
        this.setVelocity(value);
    }
    get velocity(): IPoint
    {
        return this._velocity;
    }

    /**
     * Set velocity with more broad types
     */
    private setVelocity(value: IPoint | number[])
    {
        if (Array.isArray(value))
        {
            const [x, y] = value;

            this._velocity.set(x, y);
        }
        else
        {
            this._velocity.copyFrom(value);
        }
    }

    /**
     * Handle velocity changed
     * @private
     */
    private velocityChanged()
    {
        this.uniforms.uVelocity[0] = this._velocity.x;
        this.uniforms.uVelocity[1] = this._velocity.y;

        // The padding will be increased as the velocity and intern the blur size is changed
        this.padding = (Math.max(Math.abs(this._velocity.x), Math.abs(this._velocity.y)) >> 0) + 1;
    }

    /**
     * The offset of the blur filter.
     * @default 0
     */
    set offset(value: number)
    {
        this.uniforms.uOffset = value;
    }

    get offset(): number
    {
        return this.uniforms.uOffset;
    }
}

export { MotionBlurFilter };