Optimizing Vector Rotation with Three.js Camera

Yes, there are more efficient ways to perform this rotation using Three.js built-in functionality. Your current implementation manually applies Euler angle rotations sequentially, which works but is less efficient than leveraging Three.js matrix operations.

Using Matrix4 for Rotation

Instead of manually rotating the vector with separate axis rotations, you can use the camera's world matrix directly:

TYPESCRIPTCopied
// Create a uniform that updates with the camera's world matrix
const cameraWorldMatrix = THREE.uniform("mat4").onRenderUpdate(() => {
  return camera.matrixWorld;
});

// Then to rotate your vector:
function rotateWithMatrix(vector, matrix) {
  // Create a Vector4 with w=0 (for direction vectors)
  const vec4 = vec4(vector.x, vector.y, vector.z, 0);
  
  // Apply the matrix transformation
  const rotated = mul(matrix, vec4);
  
  // Return as vec3
  return vec3(rotated.x, rotated.y, rotated.z);
}

// Usage
let dir = vec3(0.22, -1, -0.65);
dir = rotateWithMatrix(dir, cameraWorldMatrix);

This approach is more efficient because:

1. It uses a single matrix multiplication instead of three separate rotations
2. It avoids the trigonometric calculations in your current implementation
3. It directly uses the camera's world transformation

Alternative: Using Quaternion

If you prefer working with quaternions (which can be more efficient for rotations):

TYPESCRIPTCopied
const cameraWorldQuaternion = THREE.uniform("vec4").onRenderUpdate(() => {
  const q = new THREE.Quaternion();
  camera.getWorldQuaternion(q);
  return vec4(q.x, q.y, q.z, q.w);
});

// Function to rotate vector with quaternion
function rotateWithQuaternion(vector, quaternion) {
  // Implementation of quaternion rotation
  // v' = q * v * q^-1 (where q^-1 is the conjugate for unit quaternions)
  
  // Create a pure quaternion from the vector
  const vecQuat = vec4(vector.x, vector.y, vector.z, 0);
  
  // Quaternion multiplication implementation
  // This is a simplified version - you may need to implement the full quaternion multiplication
  // depending on your shader language capabilities
  
  // For TSL, you would implement quaternion rotation
  // This is conceptual pseudocode:
  const rotated = applyQuaternionToVector(quaternion, vector);
  
  return rotated;
}

Using Camera Direction Directly

If you're trying to align something with the camera's view direction:

TYPESCRIPTCopied
const cameraDirection = THREE.uniform("vec3").onRenderUpdate(() => {
  const direction = new THREE.Vector3();
  camera.getWorldDirection(direction);
  return direction;
});

// Now you can use cameraDirection directly

The matrix-based approach is generally the most straightforward and efficient for your use case, as it handles all rotation components in a single operation.