Making hull builder more robust #735
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
brianwinterpixel
pushed a commit
to winterpixelgames/box2d
that referenced
this pull request
Feb 16, 2023
nitially I tried to make gift wrapping handle collinear points better. Conclusion: gift wrapping is a bad algorithm. So I removed gift wrapping and implemented quickhull. I also added code to explicitly remove collinear points. This turns out to be quite easy once you have a convex hull. I ran over 200 million randomized tests successfully with test data that is very likely to have collinear points with small numerical deviations. All the tests passed and algorithm correctly rejects very close points and fully collinear points. I also tested performance at around 150 milliseconds per million hulls. I split out the convex hull code into a separate function b2ComputeHull. This lets people build hulls offline and check for hull validity before using them in b2PolygonShape. This video is a good reference for the 2D quickhull algorithm (my implementation is different): https://www.youtube.com/watch?v=2EKIZrimeuk Fixes: erincatto#671 erincatto#728
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Initially I tried to make gift wrapping handle collinear points better. Conclusion: gift wrapping is a bad algorithm.
So I removed gift wrapping and implemented quickhull. I also added code to explicitly remove collinear points. This turns out to be quite easy once you have a convex hull.
I ran over 200 million randomized tests successfully with test data that is very likely to have collinear points with small numerical deviations. All the tests passed and algorithm correctly rejects very close points and fully collinear points.
I also tested performance at around 150 milliseconds per million hulls.
I split out the convex hull code into a separate function
b2ComputeHull. This lets people build hulls offline and check for hull validity before using them inb2PolygonShape.This video is a good reference for the 2D quickhull algorithm (my implementation is different): https://www.youtube.com/watch?v=2EKIZrimeuk
Fixes: #671 #728