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https://issues.apache.org/jira/browse/GEOMETRY-119?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17313511#comment-17313511
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Matt Juntunen commented on GEOMETRY-119:
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bq. What about changing {{normalize()}} to return {{null}} instead of raising
an exception?
I'd prefer to keep it as-is. The IAE is more informative, telling you that an
illegal norm was found as well as telling you what it was (e.g., zero, NaN, or
infinite).
I've created a PR for the {{normalizeOrNull}} method:
[https://github.com/apache/commons-geometry/pull/143]. Let me know if you think
it's ready to go. I don't plan on actually merging anything until the PR for
GEOMETRY-115 is in, since there are conflicts between the two.
Note that this PR also addresses a normalization edge case that we weren't
handling before, where the norm is real and non-zero but its inverse is not.
This occurs, for example, with {{Vector3D.of(Double.MIN_VALUE, 0,
0).normalize()}}. Previously, this would have produced an invalid
{{Vector3D.Unit}} instance with non-real values. Now it fails.
> Vector normalizeOrDefault() method
> ----------------------------------
>
> Key: GEOMETRY-119
> URL: https://issues.apache.org/jira/browse/GEOMETRY-119
> Project: Apache Commons Geometry
> Issue Type: Improvement
> Reporter: Matt Juntunen
> Priority: Major
>
> A frequent use case when working with vectors, especially vectors coming from
> external data, is attempting to normalize the vector, and if this is not
> possible, to use an alternative value. For example, the
> {{QuaternionRotation}} code
> [here|https://github.com/apache/commons-geometry/blob/master/commons-geometry-euclidean/src/main/java/org/apache/commons/geometry/euclidean/threed/rotation/QuaternionRotation.java#L86]
> does exactly this; it attempts to normalize a vector and failing that (ie,
> if the vector is exactly zero), it returns a substitute value. The
> {{QuaternionRotation}} class is able to take advantage of our internal
> {{Vectors.tryNormalize()}} but callers outside of the library are not able to
> do so and so are left with 2 choices:
> 1. wrap the {{normalize()}} call in a try-catch and handle the exception
> thrown on illegal norm values, or
> 2. compute and test the norm prior to calling {{normalize()}} to ensure that
> the call won't fail, resulting in 2 computations of the norm.
> Neither of these options are very good.
> I propose adding a new method to the Euclidean Vector classes to handle this
> situation: {{normalizeOrDefault()}}. The method would accept a default value
> (possibly null) to return if the vector cannot be normalized. The normal
> would then only need to be computed once and an exception would not need to
> be thrown in case of failure. The behavior of the current {{normalize}}
> method would be the same.
> Examples:
> {code:java}
> // get some kind of normal, preferably vec but +z will also do
> Vector3D.Unit norm = vec.normalizeOrDefault(Vector3D.Unit.PLUS_Z);
> {code}
> {code:java}
> // throw a very use-case specific error message
> Vector3D norm = vec.normalizeOrDefault(null);
> if (norm == null) {
> throw new Exception("Invalid triangle at index " + i + ": cannot compute
> normal.");
> }
> {code}
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