Convex Hull fails to create for co-linear points

Hi, first off, many thanks for the great work in this library! We’ve been using it in an open-source library called RefineryToolkits and have found an issue that we wanted to discuss.

It seems that ConvexHull fails to be created when the input points are co-linear. Specifically, this line of code does not throw, but returns a null when points are co-linear.

            var convexHull = MIConvexHull.ConvexHull.Create(vertices);

Example

Below is a list of points with the coordinates that highlighted the failure during a recent hackathon :

X 260 Y 600
X 285 Y 600
X 310 Y 600
X 335 Y 600

To solve this in short-term, we are adding a co-linearity check in our library and handle that case separately, but was wondering if it’s something that you’d like to address in the MIConvexHull library itself so everyone has access to the fix ?

Let us know 👍

[micampbell]

yes, the nuget is updated (https://www.nuget.org/packages/MIConvexHull/) and the details of the commit are here: https://github.com/DesignEngrLab/MIConvexHull/commit/915cdb730594f388b475a0a39fff2fa4d9dd5400

[micampbell]

Well, I found an easy place to fix this. There was already a function called “FindIntermediatePointsForLongSkinny” which I was able to make a small modification to so that it would return the two extrema along the line instead of crashing. For the general case, this adds no extra time. thanks for catching this!