如何让OrbitControls沿非默认轴自动旋转？代码咨询

Great question! OrbitControls' out-of-the-box auto-rotate behavior spins around the vertical Y-axis by default, but with a few tweaks, you can make it rotate around any axis you want. Let's break this down based on your existing code and different use cases.

First, Understand the Default Behavior #

By default, OrbitControls.autoRotate works by incrementing the theta property (the angle around the Y-axis) in its internal update() method. To rotate around other axes, we need to override this logic or manually adjust the camera/controls each frame.

Your Existing Code + Required Modifications #

Your current setup is:

controls = new OrbitControls(this.camera, this.renderer.domElement);
controls.rotateSpeed = 0.4;
controls.autoRotate = true;
controls.autoRotateSpeed = 10;

To switch to a non-default axis, first disable the built-in autoRotate, then add custom rotation logic to your render loop. Here are common scenarios:

1. Auto-Rotate Around the X-Axis (Horizontal Tilt) #

This will make your camera tilt up/down continuously.

// Disable default auto-rotate first
controls.autoRotate = false;

// Add this to your render animation loop
function animate() {
  requestAnimationFrame(animate);

  // Increment phi (the angle around the X-axis)
  controls.phi += controls.autoRotateSpeed * 0.001;
  // Limit phi to avoid extreme camera angles (adjust values as needed)
  controls.phi = Math.max(0.1, Math.min(Math.PI - 0.1, controls.phi));
  
  // Update controls to apply changes
  controls.update();

  this.renderer.render(this.scene, this.camera);
}
animate();

2. Auto-Rotate Around the Z-Axis (Vertical Roll) #

For rotation around the Z-axis, we need to use a rotation matrix to adjust the camera's position relative to the controls' target:

controls.autoRotate = false;

// Define your rotation axis (Z-axis here) and speed factor
const rotateAxis = new THREE.Vector3(0, 0, 1);
const speedFactor = 0.001; // Adjust to match your desired speed

// Add to your render loop
function animate() {
  requestAnimationFrame(animate);

  // Calculate the vector from target to camera
  const cameraOffset = this.camera.position.clone().sub(controls.target);
  // Create a rotation matrix around the Z-axis
  const rotationMatrix = new THREE.Matrix4().makeRotationAxis(rotateAxis, controls.autoRotateSpeed * speedFactor);
  // Apply rotation to the offset vector
  cameraOffset.applyMatrix4(rotationMatrix);
  // Update camera position
  this.camera.position.copy(controls.target.clone().add(cameraOffset));
  // Ensure camera always looks at the target
  this.camera.lookAt(controls.target);
  
  // Sync controls with the new camera position
  controls.update();

  this.renderer.render(this.scene, this.camera);
}
animate();

3. Auto-Rotate Around a Custom Arbitrary Axis #

Want to rotate around a diagonal axis like (1, 1, 0)? Just update the rotateAxis to your desired vector (make sure to normalize it first):

const rotateAxis = new THREE.Vector3(1, 1, 0).normalize();

Key Notes #

• Always call controls.update() after making manual changes to ensure the controls sync with the camera.
• Adjust the speed multiplier (like 0.001) to match your desired rotation speed—higher values mean faster rotation.
• Limiting angles (like we did with phi) prevents the camera from flipping into unviewable positions.

内容的提问来源于stack exchange，提问作者user11114318