Body step 2.1: climbing, mantling, crawling, legs, playground, 144 Hz

- Step rule + lower-body collider: no walking onto tables, steps <= 0.35 m
- Structural hand strength: two-hand mantle/pull-up works, one hand can't
- Arms aim from the physical shoulder horizontally, keep True Body pose vertically
- Crawl pose, crawl carry, 35 deg slope limit, ground feed-forward ignores
  play-space corrections (fixes a runaway feedback loop)
- Grab static world (climbing), procedural visual legs
- Playground sandbox; menu strength slider, spectator (old drag) and turn toggles
- Physics 144 Hz with interpolation; legacy chase-body spikes pin 90 Hz
- RagdollSpike: 27 phases incl. mantle, pull-up, crawl, ledge drop, ramps

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

research/ragdoll-player-step2.md

@@ -63,3 +63,32 @@ body), `scripts/PlayerRig.cs` (XR driver + stick locomotion), regression `scenes
   `AnchorMoveMode`/`Locomotion` move the XR origin in `_Process`, which would jitter under interpolation.
 - **Anchor-grab / teleport legacy locomotion** still drive the origin. Teleports carry the body. Grab-flying upward
   now fights gravity (the body falls and the view follows it), so it effectively only pulls you along the ground.
+
+## Step 2.1 — owner playtest fixes + sandbox (2026-10-02)
+
+Owner playtest of step 2: "feels amazing for the most part". It found three problems:
+- You could walk onto the table: the body detached for a second and wobbled before settling.
+- You couldn't climb onto the table by pushing yourself up.
+- You couldn't crawl under the table.
+
+Changes and the measured reasons:
+
+| Change | Why (RagdollSpike evidence) |
+|---|---|
+| **Step rule**: ground more than `MaxStepHeight` 0.35 m above the feet isn't stood on unless the hips got up there: airborne/landing, legs tucked, or hips > 60% of hip height above it, and a second ray 12 cm behind the hips also finds it | The single pelvis ray treated a 0.725 m table under the hips as a "step" → walking onto the table |
+| **Lower-body collider** (`Legs`, 6 kg box from the hips down to a step above the feet, DRIVE from the pelvis). It slides up when crouching, and its shape is **disabled** (not just layer-cleared) and tucked into the pelvis when crawling or when the arms lift the body (mantle) | Knee-high obstacles and tables now block; steps ≤ 0.35 m pass under it. Box3D kept the old contact when only the collision layer changed, which jammed a crawl against a tunnel roof |
+| **Structural hand strength**: guide cap = lerp(40 N, 400 N, axial share of the hand error), with a 3 cm deadband | Force along the arm (pressing down on a ledge, hanging, carrying at your side) is bone-strong; across the arm it stays weak. Measured: two-hand mantle onto 0.9 m ✓, one hand ✗ (5 cm). Pull-up on a grabbed bar: two hands lift the pelvis 0.69 m, one hand 0.24 m. 12 kg at arm's length still sags (6.6 cm vs 0.9 cm close) |
+| **Arm aim from the physical shoulder**, horizontal only: the arm reaches for the real hand when the body is held away horizontally (ledge, lean-over), but keeps its True Body pose vertically | Purely camera-relative arms left the hands 26 cm short when the body was held back at a ledge. Purely physical arms fold to wherever a sagging chest is and stop being pillars, so the crawl collapsed (eye 0.14 m vs 0.42). The split fixes both |
+| **Ground feed-forward from the GOAL** (pose + ground offset) | When the floor follows up onto a ledge, pose and offset move opposite; differentiating the pose alone launched the body 1 m up |
+| **Crawl pose** (`TrueBodySolver`): when the hips would go below 0.15 m, the trunk tips toward ~83°, hips kick back; ragdoll hips take the full lean in a crawl | Crouch lean capped at 43° put the hips through the floor, so the head could never get low |
+| **Crawl carry** 300 N + torso friction 0.3 | With the torso resting on the floor, μ·weight exceeded the support-scaled carry, so stick crawling stalled (Nimso has no stick crawl at all; ours is a comfort concession) |
+| **Braced air control** 150 N, **AirSlack** 0.05 m | While mantling/hanging, the hips drift after the head; airborne, the view rides the body tightly |
+| **Climbing grabs**: `PropGrabber` welds the hand to any `StaticBody3D` under the palm (5 cm sphere) except group `no_grab` (the floor) | Pull-ups, ledges, climbing-wall holds, monkey bars |
+| **Procedural legs** (`ProceduralLegs.cs`): visual only. Planted feet, alternate stepping on 20 cm / 34° error, stride leads velocity by 0.25 s, 0.2–0.32 s steps; airborne they dangle, crawling they trail | Nimso: feet don't hold the body up |
+| **144 Hz physics + physics interpolation**. `XROrigin3D`, `TrueBody` and `PlayerRig` (ghosts) are excluded; the ragdoll is explicitly interpolated. Legacy chase-body spikes pin 90 Hz | Owner's earlier choice; the old origin-moving code runs per frame, so its subtree must not interpolate |
+| **Strength slider** (0.25–3×, scales every muscle + hand guides), **Spectator** toggle (no body, the old grab-drag flight), **Turning** snap/smooth toggle | Owner: drag movement "doesn't fit this anymore", keep it as a spectator mode |
+| **Playground** (`Playground.cs`): mantling ledges 0.3–1.5 m, a 1 m platform with stairs, an 18° ramp and a 40° ramp, a climbing wall, a pull-up bar, monkey bars, a plank bridge, loose planks, a seesaw, a hanging swing board, a crate pyramid, a 25 kg box, barrels, a balance beam, a 0.6 m crawl tunnel, a duck bar, a doorway. "Reset props" resets it | Owner: a Nimso-sandbox-like level |
+
+Ground steeper than `MaxSlopeDegrees` 35° gives no support, so the 40° ramp can't be walked up; the 18° one can.
+Still open: the shoulder cone limit (needs a fork addition). `tools/playground_shots.tscn` renders overview PNGs for
+layout checks.