116 lines
2.9 KiB
JavaScript
116 lines
2.9 KiB
JavaScript
import { MassObject } from './object.js';
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import {
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MASS_CREATION_RATE,
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DISPLAY_OBJECTS_INFO,
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MOTION_TIME_SCALE,
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} from './config.js';
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export class Objects {
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objects = [];
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creatingObject = undefined;
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selectedObject = undefined;
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constructor(sim) {
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this.sim = sim;
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}
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// Create an object with mass that grows as pointer is held down
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createObject(x, y) {
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const idx = this.objects.length;
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const obj = new MassObject(x, y, idx);
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this.creatingObject = idx;
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this.objects.push(obj);
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}
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doneCreatingObject() {
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this.creatingObject = undefined;
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}
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object(i) {
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return this.objects[i];
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}
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selectObject(i) {
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this.selectedObject = i;
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}
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deselect() {
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this.selectedObject = undefined;
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}
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getSelectedOrCreating() {
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let i = this.creatingObject ?? this.selectedObject;
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if (i !== undefined) {
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return this.objects[i];
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}
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}
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get length() {
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return this.objects.length;
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}
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objectAtLocation(x, y) {
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for (let i = 0; i < this.objects.length; i++) {
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const obj = this.objects[i];
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// If distance to object is less than object's radius, we are touching the object
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const dist = Math.pow((obj.position.x - x)**2 + (obj.position.y - y)**2, 1/2);
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if (dist <= obj.radius) {
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return i;
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}
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}
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}
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handlePointerDown({x, y}) {
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// If pointer is touching an object, select the object
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const touchingObject = this.objectAtLocation(x, y);
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if (touchingObject !== undefined) {
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this.selectObject(touchingObject);
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} else {
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// Otherwise, create a new object
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this.createObject(x, y);
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}
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}
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handlePointerUp({x, y}) {
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this.doneCreatingObject();
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this.deselect();
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}
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computeFrame(elapsedTime) {
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// If we're creating an object, increment its mass
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// with the mass creation rate accelerating over time
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if (this.creatingObject !== undefined) {
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const obj = this.objects[this.creatingObject];
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const rate = MASS_CREATION_RATE * obj.age;
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obj.mass += rate * elapsedTime;
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}
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if (this.sim.playing) {
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// Update positions. Simple Euler method for now.
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for (let i = 0; i < this.objects.length; i++) {
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const obj = this.objects[i];
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obj.position.x += obj.velocity.x * MOTION_TIME_SCALE;
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obj.position.y += obj.velocity.y * MOTION_TIME_SCALE;
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}
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}
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// Display objects info
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if (DISPLAY_OBJECTS_INFO) {
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for (let i = 0; i < this.objects.length; i++) {
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const obj = this.objects[i];
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const speed = Math.pow(obj.velocity.x ** 2 + obj.velocity.y ** 2, 1/2);
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// Invert y so that the angle is counterclockwise from x-axis
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const direction = Math.atan2(-obj.velocity.y, obj.velocity.x) * 180 / Math.PI;
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this.sim.info[`Object ${i}`] = [
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`${obj.position.x}, `,
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`${obj.position.y}, `,
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`${obj.mass.toPrecision(6)} kg, `,
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`${speed.toPrecision(2)} m/s, ${direction.toPrecision(2)}°`,
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];
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}
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}
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}
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}
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