threejs-interaction

# Three.js Interaction ## Iron Law **Always call raycaster.setFromCamera() with normalized device coordinates in range [-1, 1] — raw pixel coordinates produce silent miss-hits on all objects.** ## Quick Start ```javascript import * as THREE from "three"; import { OrbitControls } from "three/addons/controls/OrbitControls.js"; // Camera controls const controls = new OrbitControls(camera, renderer.domElement); controls.enableDamping = true; // Raycasting for click detection const raycaster = new THREE.Raycaster(); const mouse = new THREE.Vector2(); function onClick(event) { mouse.x = (event.clientX / window.innerWidth) * 2 - 1; mouse.y = -(event.clientY / window.innerHeight) * 2 + 1; raycaster.setFromCamera(mouse, camera); const intersects = raycaster.intersectObjects(scene.children); if (intersects.length > 0) { console.log("Clicked:", intersects[0].object); } } window.addEventListener("click", onClick); ``` ## Raycaster ### Basic Raycasting ```javascript const raycaster = new THREE.Raycaster(); // From camera (mouse picking) raycaster.setFromCamera(mousePosition, camera); // From any origin and direction raycaster.set(origin, direction); // origin: Vector3, direction: normalized Vector3 // Get intersections const intersects = raycaster.intersectObjects(objects, recursive); // intersects array contains: // { // distance: number, // Distance from ray origin // point: Vector3, // Intersection point in world coords // face: Face3, // Intersected face // faceIndex: number, // Face index // object: Object3D, // Intersected object // uv: Vector2, // UV coordinates at intersection // uv1: Vector2, // Second UV channel // normal: Vector3, // Interpolated face normal // instanceId: number // For InstancedMesh // } ``` ### Mouse Position Conversion ```javascript const mouse = new THREE.Vector2(); function updateMouse(event) { // For full window mouse.x = (event.clientX / window.innerWidth) * 2 - 1; mouse.y = -(event.clientY / window.innerHeight) * 2 + 1; } // For specific canvas element function updateMouseCanvas(event, canvas) { const rect = canvas.getBoundingClientRect(); mouse.x = ((event.clientX - rect.left) / rect.width) * 2 - 1; mouse.y = -((event.clientY - rect.top) / rect.height) * 2 + 1; } ``` ### Touch Support ```javascript function onTouchStart(event) { event.preventDefault(); if (event.touches.length === 1) { const touch = event.touches[0]; mouse.x = (touch.clientX / window.innerWidth) * 2 - 1; mouse.y = -(touch.clientY / window.innerHeight) * 2 + 1; raycaster.setFromCamera(mouse, camera); const intersects = raycaster.intersectObjects(clickableObjects); if (intersects.length > 0) { handleSelection(intersects[0]); } } } renderer.domElement.addEventListener("touchstart", onTouchStart); ``` ### Raycaster Options ```javascript const raycaster = new THREE.Raycaster(); // Near/far clipping (default: 0, Infinity) raycaster.near = 0; raycaster.far = 100; // Line/Points precision raycaster.params.Line.threshold = 0.1; raycaster.params.Points.threshold = 0.1; // Layers (only intersect objects on specific layers) raycaster.layers.set(1); ``` ### Efficient Raycasting ```javascript // Only check specific objects const clickables = [mesh1, mesh2, mesh3]; const intersects = raycaster.intersectObjects(clickables, false); // Use layers for filtering mesh1.layers.set(1); // Clickable layer raycaster.layers.set(1); // Throttle raycast for hover effects let lastRaycast = 0; function onMouseMove(event) { const now = Date.now(); if (now - lastRaycast < 50) return; // 20fps max lastRaycast = now; // Raycast here } ``` ## Camera Controls ### OrbitControls ```javascript import { OrbitControls } from "three/addons/controls/OrbitControls.js"; const controls = new OrbitControls(camera, renderer.domElement); // Damping (smooth movement) controls.enableDamping = true; controls.dampingFactor = 0.05; // Rotation limits controls.minPolarAngle = 0; // Top controls.maxPolarAngle = Math.PI / 2; // Horizon controls.minAzimuthAngle = -Math.PI / 4; // Left controls.maxAzimuthAngle = Math.PI / 4; // Right // Zoom limits controls.minDistance = 2; controls.maxDistance = 50; // Enable/disable features controls.enableRotate = true; controls.enableZoom = true; controls.enablePan = true; // Auto-rotate controls.autoRotate = true; controls.autoRotateSpeed = 2.0; // Target (orbit point) controls.target.set(0, 1, 0); // Update in animation loop function animate() { controls.update(); // Required for damping and auto-rotate renderer.render(scene, camera); } ``` ### Other Control Types | Control | Import | Best For | |---------|--------|----------| | `FlyControls` | `controls/FlyControls.js` | Free-flying, space/flight sims | | `FirstPersonControls` | `controls/FirstPersonControls.js` | FPS with look constraints | | `PointerLockControls` | `controls/PointerLockControls.js` | Immersive FPS (browser pointer lock) | | `TrackballControls` | `controls/TrackballControls.js` | Unconstrained rotation (rolls past poles) | | `MapControls` | `controls/MapControls.js` | Top-down map view | > Full code examples → `references/advanced-controls.md` ## TransformControls Gizmo for moving/rotating/scaling objects. ```javascript import { TransformControls } from "three/addons/controls/TransformControls.js"; const transformControls = new TransformControls(camera, renderer.domElement); scene.add(transformControls); // Attach to object transformControls.attach(selectedMesh); // Switch modes transformControls.setMode("translate"); // 'translate', 'rotate', 'scale' // Change space transformControls.setSpace("local"); // 'local', 'world' // Size transformControls.setSize(1); // Events transformControls.addEventListener("dragging-changed", (event) => { // Disable orbit controls while dragging orbitControls.enabled = !event.value; }); transformControls.addEventListener("change", () => { renderer.render(scene, camera); }); // Keyboard shortcuts window.addEventListener("keydown", (event) => { switch (event.key) { case "g": transformControls.setMode("translate"); break; case "r": transformControls.setMode("rotate"); break; case "s": transformControls.setMode("scale"); break; case "Escape": transformControls.detach(); break; } }); ``` ## DragControls Drag objects directly. ```javascript import { DragControls } from "three/addons/controls/DragControls.js"; const draggableObjects = [mesh1, mesh2, mesh3]; const dragControls = new DragControls( draggableObjects, camera, renderer.domElement, ); dragControls.addEventListener("dragstart", (event) => { orbitControls.enabled = false; event.object.material.emissive.set(0xaaaaaa); }); dragControls.addEventListener("drag", (event) => { // Constrain to ground plane event.object.position.y = 0; }); dragControls.addEventListener("dragend", (event) => { orbitControls.enabled = true; event.object.material.emissive.set(0x000000); }); ``` ## Selection System ### Click to Select ```javascript const raycaster = new THREE.Raycaster(); const mouse = new THREE.Vector2(); let selectedObject = null; function onMouseDown(event) { mouse.x = (event.clientX / window.innerWidth) * 2 - 1; mouse.y = -(event.clientY / window.innerHeight) * 2 + 1; raycaster.setFromCamera(mouse, camera); const intersects = raycaster.intersectObjects(selectableObjects); // Deselect previous if (selectedObject) { selectedObject.material.emissive.set(0x000000); } // Select new if (intersects.length > 0) { selectedObject = intersects[0].object; selectedObject.material.emissive.set(0x444444); } else { selectedObject = null; } } ``` ### Hover Effects ```javascript const raycaster = new THREE.Raycaster(); const mouse = new THREE.Vector2(); let hoveredObject = null; function onMouseMove(event) { mouse.x = (event.clientX / window.innerWidth) * 2 - 1; mouse.y = -(event.clientY / window.innerHeight) * 2 + 1; raycaster.setFromCamera(mouse, camera); const intersects = raycaster.intersectObjects(hoverableObjects); // Reset previous hover if (hoveredObject) { hoveredObject.material.color.set(hoveredObject.userData.originalColor); document.body.style.cursor = "default"; } // Apply new hover if (intersects.length > 0) { hoveredObject = intersects[0].object; if (!hoveredObject.userData.originalColor) { hoveredObject.userData.originalColor = hoveredObject.material.color.getHex(); } hoveredObject.material.color.set(0xff6600); document.body.style.cursor = "pointer"; } else { hoveredObject = null; } } window.addEventListener("mousemove", onMouseMove); ``` ## Keyboard Input ```javascript const keys = {}; document.addEventListener("keydown", (event) => { keys[event.code] = true; }); document.addEventListener("keyup", (event) => { keys[event.code] = false; }); function update() { const speed = 0.1; if (keys["KeyW"]) player.position.z -= speed; if (keys["KeyS"]) player.position.z += speed; if (keys["KeyA"]) player.position.x -= speed; if (keys["KeyD"]) player.position.x += speed; if (keys["Space"]) player.position.y += speed; if (keys["ShiftLeft"]) player.position.y -= speed; } ``` ## References - `references/advanced-controls.md` — FlyControls, FirstPersonControls, PointerLockControls, TrackballControls, MapControls; box selection; world↔screen coordinate conversion; InteractionManager class; performance tips ## See Also - `threejs-fundamentals` - Camera and scene setup - `threejs-animation` - Animating interactions - `threejs-shaders` - Visual feedback effects