A stylized robot hand made in code, no asset: rigid pieces, each fixed to
one bone, so nothing bends or stretches out of shape. A light shell per
finger bone (a tapered box with rounded edges and ends), dark balls at the
knuckles and the thumb's base, dark hinges at the other joints, a palm of a
dark core between a palm plate and a back plate with panel lines, and a
short closed cuff past the wrist. Cyan accents glow: fingertip pads, a line
across the knuckles, a dot in the palm, a ring round the cuff. solid is
ceramic white over dark grey metal; ghost is pale and see-through.
screens/handrobot.cpp builds one mesh (2373 vertices, 4360 triangles) once,
a right hand on DemoPose's open hand, in 16 segments' frames. The frames are
handskin's rule (new handskin::TrackedFrames); a left hand's are a right
one's mirrored, so the same mesh draws it mirrored. Each vertex is fixed to
its bone's start or end: shells keep their rounded ends, the straight middle
takes up the tracked length, fingertips end at the tracked tips. The vertex
shader applies one segment's matrix per vertex; no cap pass (it's closed).
Cost (--snapshot, frame-job 4 cores, same run): robot 0.21-0.24 ms CPU and
0.55-0.57 ms GPU wait per draw, against asset 0.28/0.66, babylon 0.26/0.66,
mrtk3 0.25/0.66.
Tests: segments start at their joints along their bones, no vertex past its
bone's length, fingertips at the tracked tips, left = right mirrored vertex
for vertex, rigid segments across poses, only the middle stretches with a
longer bone, accents on the right sides.
No free robot hand asset fit; screens/assets/hands/README.md says what was
looked at.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The look: no more drawn outline. The old rim pass lit a hard line wherever the
hand met the background or a part of it further back, so a finger over the palm
got scratchy white lines. Now the body pass keeps only the surface nearest the
eye (depth) and writes how squarely it faces the eye, the fade, a light from
above and how near a fingertip; the second pass turns that into a soft fresnel
rim, a slight fingertip glow and an antialiased outline. ghost glows white
toward its edges; solid is lit from above with a soft cool rim.
The wrist: the model is cut open where the fade ends, so a hand pointing away
showed its inside (a hollow tube, a fist's fingertips through the palm). A
stencil pass counts front faces up and back faces down along each view (on its
own, with the depth test off: early depth would drop hidden ones); where a view
went in through the cut, a disc where the fade begins covers it.
The models: HANDS_VIEW_MODEL=asset (generic-hand, still the default) | babylon
(Babylon.js, CC BY 4.0) | mrtk3 (BSD-3-Clause, right only, mirrored) | godot
(Godot XR Tools, CC0) | mrtk2 (MIT) | capsules. Each is in
screens/assets/hands/<name>/ with its licence and a README giving the source
commit, hashes and conversion (the MRTK ones were FBX: assimp, then the new
screens/tools/hand-glb-clean.py). hand-asset.py maps each skeleton onto WebXR's
25 joints by name and writes them all into handasset.h; handskin takes the
model's index.
Cost (--snapshot, asset): CPU 0.34 ms per draw (was 0.32-0.33), GPU wait
0.61-0.62 ms per draw (was 0.57). --snapshot now prints the GPU wait.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The rendered hands are now the WebXR Input Profiles' generic hand (MIT),
posed by the tracked skeleton and skinned on the GPU: per joint a frame
from the bone and the palm, scaled to the hand and each bone's length.
Two looks, HANDS_VIEW_STYLE=ghost|solid; HANDS_VIEW_MODEL=capsules keeps
the tube hand. With HANDS_VIEW_ROOMVIEW=1 (the default) the hands also
float over the cutout with Room View on. --snapshot draws demo poses
into a PNG without SteamVR, and the cost (0.4 ms a draw, the tubes 0.6).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
