118 lines
3.3 KiB
JavaScript
118 lines
3.3 KiB
JavaScript
import {add, copy, div, mult, sub, zero} from "./vector.js";
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export class Panning {
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sim = undefined;
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touchStart = undefined;
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touchLatest = undefined;
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paused = false;
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velocity = zero;
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constructor(sim) {
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this.sim = sim;
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}
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handlePointerDown({x, y}) {
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this.initializeTouch({x, y});
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}
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initializeTouch({x, y}) {
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this.touchStart = {
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x,
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y,
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t: this.sim.rawTime,
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viewOrigin: copy(this.sim.display.viewOrigin),
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};
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this.touchLatest = {
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...this.touchStart,
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dx: 0,
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dy: 0,
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dt: 0,
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};
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}
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// With fast panning, panning velocity calculation happens every move;
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// With normal panning, calculation only happens at pointer up.
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handlePointerMove({x, y}) {
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if (this.touchStart) {
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this.touchLatest = {
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x,
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y,
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t: this.sim.rawTime,
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dx: x - this.touchStart.x,
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dy: x - this.touchStart.y,
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dt: this.sim.rawTime - this.touchStart.t,
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};
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if (this.sim.getOption('compensate.fastPanning')) {
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this.updateVelocity();
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}
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}
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}
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handlePointerUp() {
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if (this.touchStart && this.touchLatest) {
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if (this.touchLatest.dt === 0) {
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this.velocity = zero;
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}
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this.touchStart = undefined;
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if (this.sim.getOption('compensate.fastPanning')) {
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this.velocity = zero;
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} else {
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this.updateVelocity();
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}
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}
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}
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frame(elapsedTime) {
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const {touchStart: start, touchLatest: latest} = this;
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const {display} = this.sim;
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// Direct translate, unless using fast panning
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if (start && latest && !this.sim.getOption('compensate.fastPanning')) {
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// start and latest are in screen coordinates, need to convert to sim scale
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const delta = div(sub(latest, start), display.scale);
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display.viewOrigin = sub(start.viewOrigin, delta);
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}
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// Apply update to viewOrigin based on panning
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if (!this.paused) {
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// elapsedTime is scaled by time scale, is that what we want?
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// Yes because if panning.velocity == obj.velocity, object should stay in view
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const delta = mult(this.velocity, elapsedTime);
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display.viewOrigin = add(display.viewOrigin, delta);
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}
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// Update what's considered start
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if (start && latest) {
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this.initializeTouch(this.touchLatest);
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}
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if (this.sim.getOption('debug.panningInfo')) {
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const {x, y} = this.sim.panning?.velocity ?? {};
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this.sim.info['Panning Velocity'] = [`${x?.toPrecision(6)}, `, y?.toPrecision(6)];
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const {centerOfMass} = this.sim.system.computeSystemCenter();
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this.sim.info['Center of Mass'] = [`${centerOfMass.x.toPrecision(6)}, `, centerOfMass.y.toPrecision(6)];
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this.sim.info['Net Angular Momentum'] = this.sim.system.computeSystemAngularMomentum().toPrecision(6);
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}
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}
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updateVelocity() {
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// Convert pointer velocity to simulation scale, and multiply by -1
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// because the camera is panning opposite to the pointer velocity.
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let velocity = div(this.sim.pointer.latestVelocity, -this.sim.display.scale);
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if (this.sim.getOption('compensate.timeScale')) {
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velocity = div(velocity, this.sim.timeScale);
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}
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// Also add current panning
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velocity = add(velocity, this.velocity);
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this.velocity = velocity;
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}
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setVelocity(velocity) {
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this.velocity = velocity;
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if (!this.sim.playing) {
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this.paused = true;
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}
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}
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}
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