From 0f8cab717354628e16ece23f0a7547d20ab4e087 Mon Sep 17 00:00:00 2001 From: mitiguy Date: Mon, 14 Oct 2024 18:48:11 -0700 Subject: [PATCH] Add comments to help communicate the defects in the simple mesh (with ONE face) contained in the file bad_geometry_volume_negative.obj --- geometry/test/bad_geometry_volume_negative.obj | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/geometry/test/bad_geometry_volume_negative.obj b/geometry/test/bad_geometry_volume_negative.obj index c3a05c674d94..3d554b611620 100644 --- a/geometry/test/bad_geometry_volume_negative.obj +++ b/geometry/test/bad_geometry_volume_negative.obj @@ -1,12 +1,18 @@ # File: bad_geometry_volume_negative.obj -# The geometry in this file produces invalid mass and inertia properties -# due to improper winding (order of the vertices) in its one face. -# Drake calculates a negative volume for this mesh (volume = -1.0). +# The geometry in this file does not describe a closed triangular mesh (it only +# has ONE face) and Drake's mass properties calculator produces an invalid +# volume, invalid mass, invalid center of mass, and invalid inertia matrix. +# An additional defect (which makes invalidity easier to detect) is that its one +# face has a winding (order of its vertices) that results in Drake calculating +# a negative volume for this mesh (volume = -1.0). # Related files: bad_geometry_volume_zero.obj and bad_geometry_corrected.obj # Related: issue #21924 [github.com/RobotLocomotion/drake/issues/21924]. # ------------------------------------------------------------------------------ # The 3 vertices below together with the origin (0, 0, 0) form a tetrahedron. +# Drake happens to use this single tetrahedron to calculate volume and other +# mass proeprties. However, this mesh only has ONE face, so its bounding box +# indicates a volume = 0, which is another way to detect mesh defects. v 1.0 0.0 0.0 v 1.0 2.0 0.0 v 1.0 0.0 3.0