Description

The documentation of Matrix4.lookAt(eye, target, up) says:

Constructs a rotation matrix, looking from eye towards target oriented by the up vector.

However, the implementation only overwrites 9 of the 16 elements:

		te[ 0 ] = _x.x; te[ 4 ] = _y.x; te[ 8 ] = _z.x;
		te[ 1 ] = _x.y; te[ 5 ] = _y.y; te[ 9 ] = _z.y;
		te[ 2 ] = _x.z; te[ 6 ] = _y.z; te[ 10 ] = _z.z;

As a result, the return value is not necessarily (just) a rotation matrix. I was trying to avoid allocating by re-using the same Matrix4 for multiple types of calculations. The current behavior caused some confusion, especially as it is contrary to how every other constructor that I checked works including, notably, setFromMatrix3.

Reproduction steps

Run the code and look at the output.

Code

import * as THREE from 'three';

console.log(new THREE.Matrix4().makeTranslation(42, 42, 42).lookAt(new THREE.Vector3(0, 0, 1), new THREE.Vector3(0, 0, 0), new THREE.Vector3(0, 1, 0)));

Live example

Paste the code into https://playcode.io/three

Screenshots

Workaround

matrix4.identity().lookAt(...)

Alternatives

• The documentation could be updated to mention that not all elements are overwritten.
• (Breaking change/bad idea) use the existing translation instead of the eye argument.

Version

r172

Device

Desktop

Browser

Chrome

OS

Linux