Release God's Eye View as open source

src/orbit.js

@@ -0,0 +1,91 @@
+import * as Cesium from 'cesium';
+import { holdContinuousRender, releaseContinuousRender } from './renderGovernor.js';
+
+/**
+ * OrbitController — smooth orbit around a target point.
+ * Uses scene.preRender for frame-rate-independent 60fps updates.
+ * Toggle with O key; auto-stops on POI/city change.
+ */
+export class OrbitController {
+  constructor(viewer) {
+    this.viewer = viewer;
+    this.active = false;
+    this.target = null;
+    this.radius = 500;
+    this.pitch = -30;
+    this.speed = Cesium.Math.toRadians(6); // ~6°/sec → full rotation in ~60s
+    this.angle = 0;
+    this._removeListener = null;
+  }
+
+  /**
+   * Start orbiting around a target position.
+   * @param {Cesium.Cartesian3} targetCartesian - The point to orbit around
+   * @param {object} options
+   * @param {number} options.radius - Distance from target in meters
+   * @param {number} options.pitch - Tilt angle in degrees (negative = looking down)
+   * @param {number} options.speed - Degrees per second (default 6)
+   */
+  start(targetCartesian, options = {}) {
+    if (!targetCartesian) return;
+
+    this.target = targetCartesian;
+    this.radius = options.radius || this.radius;
+    this.pitch = options.pitch || this.pitch;
+    this.speed = Cesium.Math.toRadians(options.speed || 6);
+    this.active = true;
+    // Orbit mutates the camera from preRender — without a hold the loop
+    // starves after its first idle frame. (perf wave 2)
+    holdContinuousRender('camera-orbit');
+
+    // Start from the camera's current heading for seamless transition
+    this.angle = this.viewer.camera.heading;
+
+    let lastTime = Date.now();
+    this._removeListener = this.viewer.scene.preRender.addEventListener(() => {
+      if (!this.active) return;
+
+      const now = Date.now();
+      const dt = (now - lastTime) / 1000;
+      lastTime = now;
+
+      this.angle += this.speed * dt;
+
+      const hpr = new Cesium.HeadingPitchRange(
+        this.angle,
+        Cesium.Math.toRadians(this.pitch),
+        this.radius
+      );
+      this.viewer.camera.lookAt(this.target, hpr);
+    });
+  }
+
+  /**
+   * Stop orbiting. Camera freezes at current position and user regains control.
+   */
+  stop() {
+    this.active = false;
+    releaseContinuousRender('camera-orbit');
+    if (this._removeListener) {
+      this._removeListener();
+      this._removeListener = null;
+    }
+    // Unlock camera for free interaction
+    this.viewer.camera.lookAtTransform(Cesium.Matrix4.IDENTITY);
+  }
+
+  /**
+   * Toggle orbit on/off.
+   * @param {Cesium.Cartesian3} targetCartesian - Required when starting
+   * @param {object} options - Passed to start()
+   * @returns {boolean} Whether orbit is now active
+   */
+  toggle(targetCartesian, options) {
+    if (this.active) {
+      this.stop();
+    } else {
+      this.start(targetCartesian, options);
+    }
+    return this.active;
+  }
+}