@woosh/meep-engine/src/engine/graphics/trail/x/simulator/RibbonXFixedPhysicsSimulator.js

Pure JavaScript game engine. Fully featured and production ready.

import { clamp01 } from "../../../../../core/math/clamp01.js";
import { RIBBON_ATTRIBUTE_ADDRESS_AGE, RIBBON_ATTRIBUTE_ADDRESS_UV_OFFSET } from "../ribbon_attributes_spec.js";


/**
 * Fixed function simulation engine for ribbons
 */
export class RibbonXFixedPhysicsSimulator {

    /**
     *
     * @param {RibbonX} ribbon
     * @param {number} max_age
     * @param {number} timeDelta
     */
    update(ribbon, max_age, timeDelta) {

        const n = ribbon.getCount();
        for (let i = 0; i < n; i++) {
            // age the ribbon
            const age = ribbon.incrementPointAttribute_Scalar(i, RIBBON_ATTRIBUTE_ADDRESS_AGE, timeDelta);

            const relative_age = clamp01(age / max_age);

            // apply alpha over-time
            ribbon.setPointAlpha(i, 1.0 - relative_age);

            ribbon.setPointAttribute_Scalar(i, RIBBON_ATTRIBUTE_ADDRESS_UV_OFFSET, relative_age);
        }


    }
}