Vector.normalize() needs to avoid division by zero

Current normalization code is as follows:

    public Vector3d normalize(Vector3d dest) {
        double invLength = 1.0 / length();
        dest.x = x * invLength;
        dest.y = y * invLength;
        dest.z = z * invLength;
        return dest;
    }

Instead division by zero should always be avoided, and the code should be something like the following to prevent division-by-zero (arguably dealing with a zero vector in the result is better from a robustness point of view than dealing with Inf or NaN, since these values propagate virally):

    public Vector3d normalize(Vector3d dest) {
        double lengthSq = lengthSquared();
        if (lengthSq < 1.0e-30) {
            dest.x = 0.0;
            dest.y = 0.0;
            dest.z = 0.0;
        } else {
            double invLength = 1.0 / Math.sqrt(lengthSq);
            dest.x = x * invLength;
            dest.y = y * invLength;
            dest.z = z * invLength;
        }
        return dest;
    }

Then there should be a Vector.isZero() method for quickly testing if a vector is (exactly) equal to zero, so that return conditions from methods like the result of normalize() can be quickly checked:

    public boolean isZero() {
        return x == 0.0 && y == 0.0 && z == 0.0;
    }

There should probably also be a Vector.isCloseToZero() method that would replace the if (lengthSq < 1.0e-30) test above:

    public boolean isCloseToZero() {
        double lengthSq = lengthSquared();
        return lengthSq < 1.0e-30;
    }

The constant 1.0e-30 could be smaller for float vectors (maybe 1.0e-12f) – it should be something above the precision floor, but below the probable error/noise floor for the majority of applications.

[lukehutch]

Just one thing missing… Any method that can result in NaN/infinity in any component needs to recommend in the Javadoc that the user call isFinite on the result, if there’s any chance of this happening (eg. when normalizing a zero vector).

[httpdigest]

Alright, just manually retriggered the build and this one went through, so 1.9.23-SNAPSHOT is available now.