@spearwolf/twopoint5d/lib/stage/ParallaxProjection.js

a library to create 2.5d realtime graphics and pixelart with three.js

import { PerspectiveCamera, Vector2 } from 'three';
import { ProjectionPlane } from './ProjectionPlane.js';
import { fitIntoRectangle } from './fitIntoRectangle.js';
export class ParallaxProjection {
    #viewRect = new Vector2();
    #pixelRatio = new Vector2();
    #halfHeight;
    #near;
    #far;
    #distanceToProjectionPlane;
    #aspect;
    #fovy;
    constructor(projectionPlane, specs) {
        this.projectionPlane = typeof projectionPlane === 'string' ? ProjectionPlane.get(projectionPlane) : projectionPlane;
        this.viewSpecs = specs ?? {};
    }
    updateViewRect(width, height) {
        fitIntoRectangle(new Vector2(width, height), this.viewSpecs, this.#viewRect);
        this.#halfHeight = this.#viewRect.height / 2;
        this.#pixelRatio.set(width, height).divide(this.#viewRect);
        this.#near = this.viewSpecs.near ?? 0.1;
        this.#far = this.viewSpecs.far ?? 100000;
        this.#distanceToProjectionPlane = this.viewSpecs.distanceToProjectionPlane ?? 300;
        this.#aspect = this.#viewRect.width / this.#viewRect.height;
        this.#fovy = (2 * Math.atan(this.#halfHeight / this.#distanceToProjectionPlane) * 180) / Math.PI;
    }
    getViewRect() {
        return [this.#viewRect.width, this.#viewRect.height, this.#pixelRatio.x, this.#pixelRatio.y];
    }
    createCamera() {
        const camera = new PerspectiveCamera(this.#fovy, this.#aspect, this.#near, this.#far);
        this.projectionPlane.applyRotation(camera);
        camera.position.copy(this.projectionPlane.getPointByDistance(this.#distanceToProjectionPlane));
        camera.updateProjectionMatrix();
        return camera;
    }
    updateCamera(camera) {
        camera.fov = this.#fovy;
        camera.aspect = this.#aspect;
        camera.updateProjectionMatrix();
    }
    getZoom(distanceToProjectionPlane) {
        if (distanceToProjectionPlane === 0)
            return 1;
        const d = this.#distanceToProjectionPlane - distanceToProjectionPlane;
        return (Math.tan(((this.#fovy / 2) * Math.PI) / 180) * d) / this.#halfHeight;
    }
}
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