One-way platforms, raycast and collision stay with contact data: a collider can be one-way with a side it blocks from (turning with its object, drawn thick in the scene view) and a tile can be one-way from above, one-way cells never merge with solid tiles, a contact blocks only when its normal is within 45 degrees of the blocking side, the new node Ignore one-way lets an object drop through for a while, and it all holds for Move and for dynamic bodies in Rapier, where the decision is made before each step because the hook may not touch the engine (#155); the new Raycast node answers hit, object, collider, point, normal and distance in our own f64 geometry, the same in editor run and play, and the editor run draws each ray for 0.25 s (#153); On collision stay gains an interval with its own clock per pair, and stay and enter gain the contact point next to normal and impulse (#149); fixes that every Rapier collider of a tilemap had the shape of its last cell

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/runtime/physics/PhysicsSystem.ts

@@ -2,6 +2,7 @@ import type {
   Collider,
   ColliderDesc,
   EventQueue,
+  PhysicsHooks,
   RigidBody,
   World as RapierWorld,
 } from '@dimforge/rapier2d-compat';
@@ -10,7 +11,16 @@ import { apply, determinant, IDENTITY, invert, type Mat } from '../../core/model
 import type { Vec2 } from '../../core/model/Properties';
 import { signedArea } from '../../core/model/polygon';
 import { parentChain } from '../../core/model/walk';
-import { type ColliderShape, isTrigger, shapeArea, shapesOverlap } from '../../core/properties/collider';
+import {
+  type ColliderShape,
+  contactBetween,
+  isTrigger,
+  landsOn,
+  movedShape,
+  piecesOf,
+  shapeArea,
+  shapesOverlap,
+} from '../../core/properties/collider';
 import { hasTransformProps } from '../../core/properties/PropertySchema';
 import {
   type BodyType,
@@ -27,9 +37,13 @@ import {
   bodyOf,
   type CollisionPair,
   type CollisionSource,
+  type Contact,
   type MoveResult,
   partsOf,
+  type RayFilter,
+  type RayResult,
   shapeOf,
+  type SolidShape,
   Solids,
 } from '../systems/solids';
 import type { System } from '../systems/System';
@@ -41,6 +55,11 @@ export const PHYSICS_STEP = 1 / 60;
 const MAX_STEPS_PER_TICK = 8;
 /** A pose that moved less than this (world units, radians) was not moved by anyone. */
 const POSE_EPSILON = 1e-6;
+/**
+ * How deep (world units) a body may sit in a one-way collider and still count as on top of it: the
+ * engine lets a landing sink in a little before it pushes it out (1.9 px measured at 60 Hz, #155).
+ */
+const ONE_WAY_SLOP = 2;
 
 interface Pose {
   x: number;
@@ -56,9 +75,10 @@ interface Pose {
 interface Body {
   kind: 'rigid' | 'free' | 'tilemap';
   body: RigidBody;
-  /** The engine's colliders – several for a polygon, one per convex piece – and whose each is. */
+  /** The engine's colliders – several for a polygon, one per convex piece – whose each is, and its shape. */
   colliders: Collider[];
   sources: Entity[];
+  solids: SolidShape[];
   /** What the colliders were built from; they are built again when it changes (a scaled object). */
   shapeKey: string;
   settingsKey: string;
@@ -73,10 +93,14 @@ interface Body {
   current: Pose;
 }
 
-/** An engine collider: the entity it stands for and its world shape at the last sync. */
+/**
+ * An engine collider: the entity it stands for, its world shape at the last sync and, for a one-way
+ * one, the side it blocks from (#155).
+ */
 interface Part {
   entity: Entity;
   shape: ColliderShape;
+  facing: Vec2 | null;
   owner: Body;
 }
 
@@ -101,6 +125,14 @@ export class PhysicsSystem implements System, CollisionSource {
   /** Collider handle pairs the engine reports in contact or intersecting, keyed `h1|h2`. */
   private readonly candidates = new Map<string, [number, number]>();
   private current = new Map<string, CollisionPair>();
+  /** The engine colliders each current pair was found with, `a`'s first – where its contact is read. */
+  private pairColliders = new Map<string, [number, number]>();
+  /**
+   * Pairs of a dynamic body and a one-way collider near each other, keyed `h1|h2`: whether the body
+   * passes through (#155). Decided before each step, since the engine's hook must not touch the engine.
+   */
+  private passes = new Map<string, boolean>();
+  private hooks: PhysicsHooks | null = null;
   private readonly solids = new Solids();
   private backlog = 0;
   /** The length of the frame being played – the time a move of the graph's is spread over. */
@@ -116,6 +148,12 @@ export class PhysicsSystem implements System, CollisionSource {
     this.engine = engine;
     this.queue = new this.rapier.EventQueue(true);
     this.world = world;
+    const { SolverFlags } = this.rapier;
+    this.hooks = {
+      filterContactPair: (h1, h2) =>
+        this.passes.get(handlePairKey(h1, h2)) ? SolverFlags.EMPTY : SolverFlags.COMPUTE_IMPULSE,
+      filterIntersectionPair: () => true,
+    };
   }
 
   stop(): void {
@@ -128,6 +166,9 @@ export class PhysicsSystem implements System, CollisionSource {
     this.parts.clear();
     this.candidates.clear();
     this.current = new Map();
+    this.pairColliders = new Map();
+    this.passes = new Map();
+    this.hooks = null;
     this.enters = [];
     this.stays = [];
     this.exits = [];
@@ -150,7 +191,8 @@ export class PhysicsSystem implements System, CollisionSource {
     const entered = new Set<string>();
     while (this.backlog >= PHYSICS_STEP - 1e-9 && steps < MAX_STEPS_PER_TICK) {
       for (const body of this.bodies.values()) if (body.body.isDynamic()) body.previous = body.current;
-      engine.step(this.queue!);
+      this.decideOneWay(world);
+      engine.step(this.queue!, this.hooks ?? undefined);
       for (const body of this.bodies.values()) if (body.body.isDynamic()) body.current = poseOf(body.body);
       this.collect(world, entered);
       this.backlog -= PHYSICS_STEP;
@@ -177,6 +219,17 @@ export class PhysicsSystem implements System, CollisionSource {
     return this.solids.moveAndSlide(world, entity, dx, dy, (blocked) => this.push(world, entity, blocked));
   }
 
+  raycast(world: World, from: Vec2, direction: Vec2, length: number, filter: RayFilter): RayResult | null {
+    return this.solids.raycast(world, from, direction, length, filter);
+  }
+
+  /** How a current pair touches as of the last step: read from the engine's contact. */
+  contactOf(pair: CollisionPair): Contact | null {
+    const handles = this.pairColliders.get(`${pair.a.id}|${pair.b.id}`);
+    if (!handles || !this.parts.has(handles[0]) || !this.parts.has(handles[1])) return null;
+    return this.measure(this.engine!.getCollider(handles[0]), this.engine!.getCollider(handles[1]));
+  }
+
   /** A dynamic body's velocity in world units per second; null for an object the engine does not move. */
   velocityOf(target: Entity): Vec2 | null {
     const body = this.dynamicBodyOf(target)?.body;
@@ -355,6 +408,7 @@ export class PhysicsSystem implements System, CollisionSource {
       body: this.engine!.createRigidBody(desc),
       colliders: [],
       sources: [],
+      solids: [],
       shapeKey: '',
       settingsKey: '',
       turns: false,
@@ -437,12 +491,13 @@ export class PhysicsSystem implements System, CollisionSource {
   private build(body: Body, want: Wanted, key: Entity, world: World): void {
     const shapes = this.shapesWanted(want, key, world);
     const origin = body.placed;
-    const local = shapes.map(({ entity, shape }) => ({ entity, shape, pieces: piecesInBody(origin, shape) }));
+    const local = shapes.map((solid) => ({ ...solid, pieces: piecesInBody(origin, solid.shape) }));
     const shapeKey =
       JSON.stringify(
-        local.map(({ entity, pieces }) => [
+        local.map(({ entity, pieces, facing }) => [
           entity.id,
           pieces.map(pieceKey),
+          facing && [round(facing.x), round(facing.y)],
           entity.type === 'collider' ? [isTrigger(entity.props), colliderMaterial(entity.props)] : 0,
         ]),
       ) + JSON.stringify(want.settings?.mass ?? 0);
@@ -454,27 +509,31 @@ export class PhysicsSystem implements System, CollisionSource {
       }
       body.colliders = [];
       body.sources = [];
+      body.solids = [];
       const mass = want.settings?.mass ?? 0;
       const area = local.reduce(
         (sum, { entity, shape }) => sum + (isSolid(entity) ? shapeArea(shape) : 0),
         0,
       );
-      for (const { entity, shape, pieces } of local)
+      for (const { entity, shape, facing, pieces } of local)
         for (const piece of pieces) {
           const share = mass > 0 && area > 0 ? (mass * pieceArea(piece)) / area : 0;
-          const desc = this.colliderDesc(entity, piece, share);
+          const desc = this.colliderDesc(entity, piece, share, facing !== null);
           if (!desc) continue;
           const collider = this.engine!.createCollider(desc, body.body);
           body.colliders.push(collider);
           body.sources.push(entity);
-          this.parts.set(collider.handle, { entity, shape, owner: body });
+          body.solids.push({ shape, facing });
+          this.parts.set(collider.handle, { entity, shape, facing, owner: body });
         }
     }
-    // Shapes are refreshed every tick even when the colliders stay: the overlap test reads them.
-    const shapeOfEntity = new Map(local.map(({ entity, shape }) => [entity, shape]));
+    // Shapes are refreshed every tick even when the colliders stay: the overlap test reads them. A
+    // tilemap's many shapes all stand for the one map, so its colliders keep the shape they were built from.
+    const solidOfEntity = new Map(local.map((solid) => [solid.entity, solid]));
     body.colliders.forEach((collider, i) => {
       const entity = body.sources[i]!;
-      this.parts.set(collider.handle, { entity, shape: shapeOfEntity.get(entity)!, owner: body });
+      const { shape, facing } = body.kind === 'tilemap' ? body.solids[i]! : solidOfEntity.get(entity)!;
+      this.parts.set(collider.handle, { entity, shape, facing, owner: body });
       const on = isHandleEnabled(entity);
       if (collider.isEnabled() === on) return;
       collider.setEnabled(on);
@@ -491,14 +550,16 @@ export class PhysicsSystem implements System, CollisionSource {
     }
   }
 
-  private shapesWanted(want: Wanted, key: Entity, world: World): { entity: Entity; shape: ColliderShape }[] {
+  private shapesWanted(want: Wanted, key: Entity, world: World): (SolidShape & { entity: Entity })[] {
     if (want.kind === 'tilemap')
-      return this.solids.shapesOf(world, key).map((shape) => ({ entity: key, shape }));
-    return want.colliders.map((entity) => ({ entity, shape: shapeOf(entity) }));
+      return this.solids.solidShapesOf(world, key).map((solid) => ({ ...solid, entity: key }));
+    return want.colliders.flatMap((entity) =>
+      this.solids.solidShapesOf(world, entity).map((solid) => ({ ...solid, entity })),
+    );
   }
 
   /** The engine collider of one piece; null for a piece of no size, which the engine would refuse. */
-  private colliderDesc(entity: Entity, piece: Piece, mass: number): ColliderDesc | null {
+  private colliderDesc(entity: Entity, piece: Piece, mass: number, oneWay: boolean): ColliderDesc | null {
     const R = this.rapier;
     if (pieceArea(piece) <= 0) return null;
     let desc: ColliderDesc | null;
@@ -531,9 +592,80 @@ export class PhysicsSystem implements System, CollisionSource {
     else desc.setDensity(material.density);
     desc.setActiveEvents(R.ActiveEvents.COLLISION_EVENTS);
     desc.setActiveCollisionTypes(R.ActiveCollisionTypes.ALL);
+    if (oneWay && isSolid(entity)) desc.setActiveHooks(R.ActiveHooks.FILTER_CONTACT_PAIRS);
     return desc;
   }
 
+  /**
+   * Whether each dynamic body near a one-way collider passes through it in the coming step (#155).
+   * It lands when it is on the blocking side (or sunk in no deeper than a landing sinks), the contact
+   * faces that side within 45° and it is not moving away from it; a body that landed is held as long
+   * as the two overlap, however deep a fast fall took it in one step. Otherwise it passes – from
+   * below, from the side, from inside – and so does a body told to ignore one-way colliders. One that
+   * is to pass is woken: a resting body sleeps, and a new answer alone would not move it.
+   */
+  private decideOneWay(world: World): void {
+    const platforms: [number, Part][] = [];
+    const movers: [number, Part][] = [];
+    for (const [handle, part] of this.parts) {
+      if (!isHandleEnabled(part.entity) || !isSolid(part.entity)) continue;
+      if (part.facing) platforms.push([handle, part]);
+      else if (part.owner.kind === 'rigid' && part.owner.body.isDynamic()) movers.push([handle, part]);
+    }
+    const decided = new Map<string, boolean>();
+    for (const [hp, platform] of platforms) {
+      const surface = this.shapeNow(platform);
+      const facing = this.facingNow(platform);
+      const vp = platform.owner.body.linvel();
+      for (const [hm, mover] of movers) {
+        if (mover.owner === platform.owner) continue;
+        const shape = this.shapeNow(mover);
+        const vm = mover.owner.body.linvel();
+        const relative = { x: toPixels(vm.x - vp.x), y: toPixels(vm.y - vp.y) };
+        const margin = Math.hypot(relative.x, relative.y) * PHYSICS_STEP * 2 + 16;
+        if (Math.hypot(shape.x - surface.x, shape.y - surface.y) > reachOf(shape) + reachOf(surface) + margin)
+          continue;
+        const key = handlePairKey(hp, hm);
+        const contact = contactBetween(shape, surface, relative);
+        const lands =
+          contact.separation >= -ONE_WAY_SLOP &&
+          landsOn(contact.normal, facing) &&
+          relative.x * facing.x + relative.y * facing.y <= 1e-3;
+        const held = this.passes.get(key) === false && contact.separation < 0;
+        const passes = world.ignoresOneWay(mover.entity) || (!lands && !held);
+        if (passes && mover.owner.body.isSleeping()) mover.owner.body.wakeUp();
+        decided.set(key, passes);
+      }
+    }
+    this.passes = decided;
+  }
+
+  /** A part's shape where the engine has its body now: a dynamic body has moved on since the sync. */
+  private shapeNow(part: Part): ColliderShape {
+    const body = part.owner;
+    if (!body.body.isDynamic()) return part.shape;
+    const from = body.placed;
+    const to = poseOf(body.body);
+    const turn = to.angle - from.angle;
+    const cos = Math.cos(turn);
+    const sin = Math.sin(turn);
+    const move = (p: Vec2): Vec2 => {
+      const dx = p.x - from.x;
+      const dy = p.y - from.y;
+      return { x: to.x + dx * cos - dy * sin, y: to.y + dx * sin + dy * cos };
+    };
+    return movedShape(part.shape, move, turn);
+  }
+
+  private facingNow(part: Part): Vec2 {
+    const facing = part.facing!;
+    if (!part.owner.body.isDynamic()) return facing;
+    const turn = part.owner.body.rotation() - part.owner.placed.angle;
+    const cos = Math.cos(turn);
+    const sin = Math.sin(turn);
+    return { x: facing.x * cos - facing.y * sin, y: facing.x * sin + facing.y * cos };
+  }
+
   /**
    * The pairs in contact after a step, compared with those before it. The engine proposes the
    * pairs; where no dynamic body takes part, the overlap test decides as it always did.
@@ -571,32 +703,58 @@ export class PhysicsSystem implements System, CollisionSource {
       now.set(pairKey, { a: p.entity, b: q.entity });
       first.set(pairKey, [this.engine!.getCollider(c1), this.engine!.getCollider(c2)]);
     }
+    this.pairColliders = new Map();
     for (const [key, pair] of now) {
+      const [c1, c2] = first.get(key)!;
+      this.pairColliders.set(key, [c1.handle, c2.handle]);
       if (this.current.has(key)) {
         now.set(key, this.current.get(key)!);
         continue;
       }
-      const [c1, c2] = first.get(key)!;
-      this.enters.push(Object.assign(pair, this.contactOf(c1, c2)));
+      this.enters.push(Object.assign(pair, this.measure(c1, c2)));
       entered.add(key);
     }
     for (const [key, pair] of this.current) if (!now.has(key)) this.exits.push(pair);
     this.current = now;
   }
 
-  /** How the pair met: the normal from the second collider towards the first, and the impulse. */
-  private contactOf(c1: Collider, c2: Collider): { normal: Vec2; impulse: number } {
+  /**
+   * How the pair touches: the normal from the second collider towards the first, the impulse of the
+   * last step and the middle of the contact points (world units; zero without a contact).
+   */
+  private measure(c1: Collider, c2: Collider): Contact {
     let normal = { x: 0, y: 0 };
     let impulse = 0;
+    let sum = { x: 0, y: 0 };
+    let points = 0;
     this.engine!.contactPair(c1, c2, (manifold, flipped) => {
       if (manifold.numContacts() === 0) return;
       const n = manifold.normal();
       // The manifold's normal runs from its first collider to its second; ours runs back to `a`.
       const sign = flipped ? 1 : -1;
       if (normal.x === 0 && normal.y === 0) normal = { x: sign * n.x, y: sign * n.y };
-      for (let i = 0; i < manifold.numContacts(); i++) impulse += manifold.contactImpulse(i);
+      // Each of its points has a side on either collider, in that collider's space: the contact
+      // point is the middle of the two, which is also where two bodies that sank in meet.
+      const [first, second] = flipped ? [c2, c1] : [c1, c2];
+      const toWorld = (collider: Collider, p: { x: number; y: number }) => {
+        const at = collider.translation();
+        const cos = Math.cos(collider.rotation());
+        const sin = Math.sin(collider.rotation());
+        return { x: at.x + p.x * cos - p.y * sin, y: at.y + p.x * sin + p.y * cos };
+      };
+      for (let i = 0; i < manifold.numContacts(); i++) {
+        impulse += manifold.contactImpulse(i);
+        const p1 = manifold.localContactPoint1(i);
+        const p2 = manifold.localContactPoint2(i);
+        if (!p1 || !p2) continue;
+        const a = toWorld(first, p1);
+        const b = toWorld(second, p2);
+        sum = { x: sum.x + (a.x + b.x) / 2, y: sum.y + (a.y + b.y) / 2 };
+        points++;
+      }
     });
-    return { normal, impulse: toPixels(impulse) };
+    const point = points > 0 ? { x: toPixels(sum.x / points), y: toPixels(sum.y / points) } : { x: 0, y: 0 };
+    return { normal, impulse: toPixels(impulse), point };
   }
 
   /**
@@ -628,6 +786,18 @@ interface Wanted {
   colliders: Entity[];
 }
 
+function handlePairKey(h1: number, h2: number): string {
+  return h1 < h2 ? `${h1}|${h2}` : `${h2}|${h1}`;
+}
+
+/** How far the shape reaches from its centre. */
+function reachOf(shape: ColliderShape): number {
+  let reach = 0;
+  for (const { points, r } of piecesOf(shape))
+    for (const p of points) reach = Math.max(reach, Math.hypot(p.x - shape.x, p.y - shape.y) + r);
+  return reach;
+}
+
 function poseOf(body: RigidBody): Pose {
   const t = body.translation();
   return { x: toPixels(t.x), y: toPixels(t.y), angle: body.rotation() };