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feat: enhance pinch-to-zoom with two-finger pan support for touch devices

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CNCKitchen
2026-04-01 15:04:47 +02:00
parent fd6eae9fb5
commit 80f597141c
1 changed files with 32 additions and 16 deletions
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js/viewer.js
+32 -16
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@@ -269,14 +269,16 @@ export function initViewer(canvas) {
}
});
// Pinch-to-zoom for touch devices
// Pinch-to-zoom + two-finger pan for touch devices
let _pinchDist = null;
let _pinchMid = null; // { x, y } client coords of two-finger midpoint
renderer.domElement.addEventListener('touchstart', (e) => {
if (e.touches.length === 2) {
const t0 = e.touches[0], t1 = e.touches[1];
_pinchDist = Math.hypot(t1.clientX - t0.clientX, t1.clientY - t0.clientY);
controls.enabled = false; // suppress OrbitControls panning during pinch
_pinchMid = { x: (t0.clientX + t1.clientX) / 2, y: (t0.clientY + t1.clientY) / 2 };
controls.enabled = false; // suppress OrbitControls during two-finger gesture
e.preventDefault();
}
}, { passive: false });
@@ -285,31 +287,45 @@ export function initViewer(canvas) {
if (e.touches.length !== 2 || _pinchDist === null) return;
e.preventDefault();
const t0 = e.touches[0], t1 = e.touches[1];
const newDist = Math.hypot(t1.clientX - t0.clientX, t1.clientY - t0.clientY);
const factor = newDist / _pinchDist;
_pinchDist = newDist;
// Midpoint in NDC — zoom toward the centre of the two fingers
const rect = renderer.domElement.getBoundingClientRect();
const midX = (t0.clientX + t1.clientX) / 2;
const midY = (t0.clientY + t1.clientY) / 2;
const ndcX = ((midX - rect.left) / rect.width) * 2 - 1;
const ndcY = -((midY - rect.top) / rect.height) * 2 + 1;
const before = new THREE.Vector3(ndcX, ndcY, 0).unproject(camera);
const newDist = Math.hypot(t1.clientX - t0.clientX, t1.clientY - t0.clientY);
const midX = (t0.clientX + t1.clientX) / 2;
const midY = (t0.clientY + t1.clientY) / 2;
// ── Pan: shift camera so the world point under the old midpoint
// is now under the new midpoint ──────────────────────────
const prevNdcX = ((_pinchMid.x - rect.left) / rect.width) * 2 - 1;
const prevNdcY = -((_pinchMid.y - rect.top) / rect.height) * 2 + 1;
const curNdcX = ((midX - rect.left) / rect.width) * 2 - 1;
const curNdcY = -((midY - rect.top) / rect.height) * 2 + 1;
const prevWorld = new THREE.Vector3(prevNdcX, prevNdcY, 0).unproject(camera);
const curWorld = new THREE.Vector3(curNdcX, curNdcY, 0).unproject(camera);
const panDelta = prevWorld.sub(curWorld);
camera.position.add(panDelta);
controls.target.add(panDelta);
// ── Zoom: zoom toward the current midpoint ────────────────────────
const factor = newDist / _pinchDist;
const before = new THREE.Vector3(curNdcX, curNdcY, 0).unproject(camera);
camera.zoom = Math.max(0.05, Math.min(200, camera.zoom * factor));
camera.updateProjectionMatrix();
const after = new THREE.Vector3(ndcX, ndcY, 0).unproject(camera);
const after = new THREE.Vector3(curNdcX, curNdcY, 0).unproject(camera);
const delta = before.clone().sub(after);
camera.position.add(delta);
controls.target.add(delta);
const zoomDelta = before.clone().sub(after);
camera.position.add(zoomDelta);
controls.target.add(zoomDelta);
_pinchDist = newDist;
_pinchMid = { x: midX, y: midY };
controls.update();
}, { passive: false });
renderer.domElement.addEventListener('touchend', (e) => {
if (e.touches.length < 2) {
_pinchDist = null;
_pinchMid = null;
controls.enabled = true;
}
});