Connect native stalled grind release phase and outward exit forces

crates/skate-core/src/physics/grind_forces.rs

@@ -164,3 +164,41 @@ fn cross(a: V, b: V) -> V {
         0.0,
     ]
 }
+
+/// Grind PreUpdate82D3F4E8 / exit decision82D40DA0. Counts are native
+/// simulation updates, not render frames. Once leaving, the phase is latched.
+#[derive(Default)]
+pub struct Release {
+    updates: u32,
+    leaving_updates: u32,
+    pub leaving: bool,
+}
+impl Release {
+    pub fn begin_update(&mut self, speed: f32, explicit_exit: bool) {
+        self.leaving |= explicit_exit || (self.updates > 60 && speed < 0.15);
+    }
+    pub fn finish_update(&mut self) -> bool {
+        self.leaving_updates = if self.leaving { self.leaving_updates.wrapping_add(1) } else { 0 };
+        self.updates = self.updates.wrapping_add(1);
+        self.leaving_updates > 35
+    }
+}
+
+///82D3F850: push away from the contacted edge until the native lateral
+///speed limit is reached. Ledge engagement may supply its outward direction.
+pub fn release_force(
+    position: V, point: V, direction: V, normal: V, velocity: V,
+    surface_kind: u32, surface_side: V, force_across: bool,
+    strength: f32, speed_limit: f32, lift: f32,
+) -> V {
+    let outward = if !force_across && surface_kind != 0 {
+        scale(surface_side, -1.0)
+    } else {
+        let across = cross(direction, normal);
+        scale(across, if dot3(across, sub(position, point)) > 0.0 { 1.0 } else { -1.0 })
+    };
+    if dot3(velocity, outward) >= speed_limit { return [0.0; 4]; }
+    let lateral = scale(outward, strength);
+    let upward = normal[1].max(0.0) * lift;
+    core::array::from_fn(|i| normal[i].mul_add(upward, lateral[i]))
+}

crates/skate-game/src/physics/grind.rs

@@ -37,6 +37,7 @@ pub(crate) struct Runtime {
     test_depth_epsilon: f32,
     test_depth: f32,
     exiting: bool,
+    release: grind_forces::Release,
     surface_kind: u32,
     surface_normal: V,
     surface_side: V,
@@ -80,6 +81,7 @@ impl Runtime {
             test_depth_epsilon: data.float("physics_grinds", "default", "TestDepthEpsilon")?,
             test_depth: data.float("physics_grinds", "default", "TestDepth")?,
             exiting: false,
+            release: grind_forces::Release::default(),
             surface_kind: 0,
             surface_normal: [0.0, 1.0, 0.0, 0.0],
             surface_side: [0.0; 4],
@@ -492,6 +494,7 @@ pub(super) fn enter(physics: &mut GamePhysics, skater: &mut SkaterRuntime) -> Re
             | PhysicalStateId::GrindDarkslide
     );
     physics.grind.exiting = false;
+    physics.grind.release = grind_forces::Release::default();
     physics.grind.distance = 0.0;
     physics.grind.previous_position = super::solve::deck_frame(&physics.board)[3];
     skater.ground_lifecycle.skeleton_elapsed_16505 = true;
@@ -530,6 +533,20 @@ pub(super) fn update(physics: &mut GamePhysics, skater: &mut SkaterRuntime) -> R
     physics.grind.launched = false;
     let board = super::solve::deck_frame(&physics.board);
     let p = &skater.player_input.processed;
+    if physics.grind.active {
+        //82D40D90; Boardslide82D41788 only exposes this exit on kind2.
+        let explicit = p.flags_2476 & 0x2000_0000 != 0
+            && (!matches!(physics.grind.kind, 1 | 5) || physics.grind.surface_kind == 2);
+        let was_leaving = physics.grind.release.leaving;
+        physics.grind.release.begin_update(p.scalar_2652, explicit);
+        if !was_leaving && physics.grind.release.leaving {
+            bevy::log::info!("GRIND_RELEASE kind={} speed={} explicit={}", physics.grind.kind, p.scalar_2652, explicit);
+        }
+        if physics.grind.release.finish_update() {
+            //82D3F638: byte37/value124, using the retained request owner.
+            skater.wipeout.state.request(17, 0.0);
+        }
+    }
     if physics.grind.active && p.flags_2468 & 0x00400000 != 0 {
         let c = physics
             .grind
@@ -604,6 +621,31 @@ pub(super) fn update(physics: &mut GamePhysics, skater: &mut SkaterRuntime) -> R
             grind_contact::upright_normal(c.direction)
         };
         physics.grind.crouch = dot3(board[2], normal).abs() * 0.4;
+        if physics.grind.release.leaving {
+            let surface = physics.grind.surface_kind;
+            let (strength, limit, lift, force_across) = match physics.grind.kind {
+                //50-50 exit82D41DF0, 5-O exit82D428C0.
+                0 => if surface < 2 { (100.0, 1.0, 125.0, false) } else { (10.0, 1.0, 0.0, false) },
+                3 => if surface < 2 { (120.0, 0.9, 125.0, false) } else { (10.0, 0.9, 0.0, false) },
+                //Static rail Tipslide82D420A0 and Backslash82D42A80.
+                2 => (100.0, 1.5, 0.0, true),
+                4 => (100.0, 0.75, if surface == 1 { 125.0 } else { 0.0 }, surface == 1),
+                //Boardslide82D41250 enters the existing runout/wipeout path
+                //on rail/ledge engagement; kind2 uses a physical side force.
+                _ => (90.0, 0.75, 0.0, false),
+            };
+            if matches!(physics.grind.kind, 1 | 5) && surface != 2 {
+                skater.wipeout.state.request(10, 0.0);
+            } else {
+                append(physics, grind_forces::release_force(
+                    board[3], c.centre, c.direction, normal, velocity, surface,
+                    physics.grind.surface_side, force_across, strength, limit, lift,
+                ))?;
+            }
+            physics.riding.update_grind_reckoning(
+                &mut skater.air_reckoning.state, normal, board[2], p.flags_2468, 0.9);
+            return super::input_phase::update_ground(physics, skater);
+        }
         let across = cross(c.direction, normal);
         physics.grind.control.update(
             physics.grind.kind,

docs/grind-release.md

@@ -0,0 +1,31 @@
+# Grind release at low speed and rail ends
+
+TU3 reference: default_82000000_011B0000.bin, base82000000,
+SHA256 f4aa113eb541bfba03dbc108cf5ab43f58c965b20fa3b82f9c40938a0ad841c4.
+Static generated instruction extracts are under logs/biped-<address>.txt.
+
+Observed: PreUpdate82D3F4E8 owns a latched leaving phase. Decision82D40DA0
+enters it after more than60 state updates when Processed2652 speed is below
+0.15m/s, or on the family exit condition. It dispatches exit forces instead
+of the ordinary holding-force update. More than35 leaving updates requests
+native reason17. The previous host never ran this phase and continued pinning
+and orienting the board while stationary.
+
+Connected Release state and the existing physical body/force/request owners.
+50-50 exit82D41DF0 uses100 side/125 lift below investigation kind2, otherwise
+10 side/0 lift, capped by outward speed1.0. Helper82D3F850 uses the actual
+contact side and support normal. Other static-rail families use their native
+exit calls82D428C0/82D420A0/82D42A80/82D41250. Ordinary friction/pinning and
+orientation updates do not run during release. GRIND_RELEASE records the
+transition during user gameplay.
+
+Endpoint queries already clip segment intersections to[0,1]; losing the last
+contact makes the existing selector enter Nonspecific701 and disable the
+hook, then choose airborne/ground from actual contacts. No infinite extension
+or endpoint teleport was added. The release phase addresses a board that
+stalls while its last truck/tip remains supported at an endpoint.
+
+Scope: common slow-speed/explicit release and static-rail exit forces.
+Specialized tipslide drop-in and investigation-driven early-exit branches
+remain separate existing gaps; this does not claim full retail parity.
+Build only, no tests or automated gameplay. Visual checking is left to user.