Rotating Cone Geometry to Point Toward Origin

The issue you're experiencing is related to how the ConeGeometry is oriented by default and how the lookAt() method works with meshes.

The Problem

By default, a ConeGeometry in Three.js is created with its central axis along the Y-axis, with the tip pointing upward (+Y direction). When you use lookAt(), it orients the object's Z-axis toward the target point, not the cone's axis.

Solution

To make your cone point toward the origin [0,0,0], you need to:

1. Create a group to hold your cone
2. Rotate the cone within the group to align its axis with the Z-axis
3. Position the group at the speaker's location
4. Use lookAt() on the group

Here's a corrected approach:

JAVASCRIPTCopied
// Create a group to hold the cone
const coneGroup = new THREE.Group();

// Create the cone geometry (pointing up along Y-axis by default)
const cone = new THREE.ConeGeometry(5, 20);
const material = new THREE.MeshBasicMaterial({color: 0xffff00});
const coneMesh = new THREE.Mesh(cone, material);

// Rotate the cone to align its axis with the Z-axis (90 degrees around X)
coneMesh.rotation.x = -Math.PI / 2;

// Add the cone to the group
coneGroup.add(coneMesh);

// Position the group at the speaker's location
// Replace these coordinates with your speaker's position
coneGroup.position.set(speakerX, speakerY, speakerZ);

// Make the group look at the origin
coneGroup.lookAt(0, 0, 0);

// Add the group to the scene
scene.add(coneGroup);

For Multiple Speakers on a Convex Hull

If you have multiple speaker-cone pairs positioned on a convex hull, you can use the same approach for each pair:

JAVASCRIPTCopied
function createSpeakerWithCone(position) {
    // Create a group for this speaker-cone pair
    const group = new THREE.Group();
    
    // Create the speaker (box)
    const boxGeometry = new THREE.BoxGeometry(3, 3, 3);
    const boxMaterial = new THREE.MeshBasicMaterial({color: 0x444444});
    const boxMesh = new THREE.Mesh(boxGeometry, boxMaterial);
    group.add(boxMesh);
    
    // Create the cone
    const coneGeometry = new THREE.ConeGeometry(5, 20);
    const coneMaterial = new THREE.MeshBasicMaterial({color: 0xffff00, transparent: true, opacity: 0.5});
    const coneMesh = new THREE.Mesh(coneGeometry, coneMaterial);
    
    // Rotate the cone to align with Z-axis
    coneMesh.rotation.x = -Math.PI / 2;
    
    // Position the cone relative to the box (adjust as needed)
    coneMesh.position.z = 10; // Move the cone outward from the box
    
    group.add(coneMesh);
    
    // Position the entire group at the specified position
    group.position.copy(position);
    
    // Make the group look at the origin
    group.lookAt(0, 0, 0);
    
    return group;
}

// Example usage for multiple speakers on a convex hull
const speakerPositions = [
    new THREE.Vector3(50, 0, 0),
    new THREE.Vector3(0, 50, 0),
    new THREE.Vector3(0, 0, 50),
    // Add more positions as needed
];

speakerPositions.forEach(position => {
    const speakerWithCone = createSpeakerWithCone(position);
    scene.add(speakerWithCone);
});

This approach ensures that each cone is properly oriented with its base at the speaker and its tip pointing away from the origin.