The measurement was comparing skinned lengths against BIND-POSE lengths. A
character is never in bind pose, so ordinary posing registered as deformation:
with the animation frozen it still reported 0.42x-2.56x edge ratios, and during
a run it reported edges collapsing to 0.08x and blowing out to 5.2x. Those
numbers were an artefact of the metric, not the model.
The baseline is now built from the skeleton's REST transforms, so every ratio
reads exactly 1.00 on an unposed model and the tool validates itself. Corrected
readings on Taila through the full runtime stack, worst over run, walk, jump,
fall, slide and dash:
lengthwise stretch 1.07 Body, 1.08 ClothB, 1.09 ClothCAndW, 1.03 shell
cross-section 0.97-0.99 knee, 0.85 hip, 0.92-0.94 ankle
That is ordinary linear-blend skinning.
Also records, in the header, the two ways this measurement was previously wrong,
because both nearly produced a bad "fix":
* the bind-pose baseline above;
* flagging vertices weighted across "non-adjacent" leg bones with
max_slot - min_slot >= 2, which flags shin+foot+toe — a perfectly normal
contiguous run. A repair pass built on that was written and reverted before
it shipped; it was stripping legitimate toe and shin influences.
Checks that did come back clean and are worth not repeating: bone pose bases are
pure rotations to 0.00001, bone lengths never drift from their rest offsets, and
of 4019 coincident-vertex groups not one carries mismatched weights, so there
are no split seams tearing at the joints.
No character or gameplay code changed. skin_leg_repair.gd is byte-identical in
behaviour to the last commit; only its header comment gained a pointer to this
tool.
Co-Authored-By: Claude Opus 4.8 <[email protected]>
Adds debug/limb_deform_check.gd, which skins the leg vertices by hand and
compares them against the rest pose across a sweep of run, walk, jump, fall,
slide and dash. It reports lengthwise stretch (bending a knee can only shrink
this, so growth is genuine stretching) and cross-section loss (the linear-blend
"candy wrapper" collapse at a bent joint).
No gameplay or character code changes in this commit. Current readings on
Taila, through the full runtime stack:
lengthwise stretch 1.05 worst (Body, ClothB, ClothCAndW), 1.03 outline shell
cross-section 0.93 knee, 0.84 hip, 0.91 ankle
Sanity check on the method: the measured rest span of the leg vertex cloud is
0.818 m against 0.843 m of thigh+shin bone length, so the skinning maths is
producing real positions rather than plausible-looking noise.
That is ordinary linear-blend skinning. Combined with the earlier findings — no
bone pose basis deviating from a pure rotation by more than 0.00001, and no
bone length drifting by more than 0.0000 m — the leg geometry is not squashing
or stretching in any measurable way, so there is nothing here to fix blind.
Committing the instrument so the next round starts from a number.
Co-Authored-By: Claude Opus 4.8 <[email protected]>
Nicholas Butzke