Prevent round_corners() failures for collinear vertices - #4906
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behackl merged 1 commit intoAug 1, 2026
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Fixes ManimCommunity#3052 When three consecutive vertices of a Polygram are collinear, the turn at a corner is (near) 180 degrees, which makes tan(angle / 2) diverge to infinity. This previously produced either astronomically large coordinates (default round_corners) or an 8.70 PiB MemoryError when anchors were evenly distributed. Clamp cut_off_length to at most half the shorter adjacent edge so the rounded arc endpoints can never be pushed to infinity.
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round_corners() failures for collinear vertices
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Summary
Fixes #3052.
Polygram.round_cornerscomputes the distance between a corner vertex and the start of the rounded arc as:When three consecutive vertices are collinear, one corner forms a (near) 180 degree turn, so
tan(angle / 2)diverges to infinity. This previously produced either astronomically large coordinates (defaultround_corners, e.g. ~2.4e15) or an8.70 PiBMemoryErrorwhen anchors were evenly distributed.This PR clamps
cut_off_lengthto at most half the shorter adjacent edge vianp.clip, so the rounded arc endpoints can never be pushed to infinity. The degenerate collinear case now yields a finite, valid mobject.Changes
manim/mobject/geometry/polygram.py: clampcut_off_lengthto[-max_cut_off, max_cut_off]wheremax_cut_off = min(|vect1|, |vect2|) / 2.tests/module/mobject/geometry/test_unit_geometry.py: addtest_round_corners_collinear_points_stays_finitecovering bothround_cornersmodes.Test plan
pytest tests/module/mobject/geometry/test_unit_geometry.py -k round_cornerspasses; full file 13 passed locally.Notes
Earlier attempts #4835 and #4873 were closed; this PR applies the same validated clamp direction with a regression test and a clean commit.