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/systems/BehaviorSystem.ts

@@ -18,7 +18,7 @@ import {
 } from '../../core/graph';
 import { stepKeyRepeat } from '../../core/graph/keyRepeat';
 import { graphLookup } from '../../core/model/graphLookup';
-import { type PropertyBag, textOf } from '../../core/model/Properties';
+import { type PropertyBag, textOf, type Vec2 } from '../../core/model/Properties';
 import { findAssetOf, findScene, type Project } from '../../core/model/Project';
 import { soundFileOf } from '../../core/model/sound';
 import { parentChain } from '../../core/model/walk';
@@ -30,7 +30,7 @@ import type { World } from '../World';
 import type { Rapier } from '../physics/engine';
 import { PhysicsSystem } from '../physics/PhysicsSystem';
 import { CollisionSystem } from './CollisionSystem';
-import { bodyOf, type CollisionPair, type CollisionSource, NOT_BLOCKED } from './solids';
+import { bodyOf, type CollisionPair, type CollisionSource, type Contact, NOT_BLOCKED } from './solids';
 import { AnimationSystem } from './AnimationSystem';
 import type { Input } from './Input';
 import type { System } from './System';
@@ -68,6 +68,13 @@ const NO_DYNAMIC_BODY =
 /** How often state events may cause the next move before the run is called endless. */
 const MAX_STATE_ROUNDS = 100;
 
+/** A collision pair seen from one behavior's body: its own collider and the one across. */
+interface Side {
+  pair: CollisionPair;
+  own: Entity;
+  other: Entity;
+}
+
 interface Instance {
   entity: Entity;
   interpreter: GraphInterpreter;
@@ -387,7 +394,7 @@ export class BehaviorSystem implements System {
               i.fire('OnTimer', ctx, {}, (n) => n.id === node.id);
             }
           }
-          this.fireCollisions(instance, i, ctx);
+          this.fireCollisions(instance, i, ctx, dt);
           this.fireAnimationsFinished(instance, i, ctx);
           // With an owner the click has to land on it; a behavior without one has no shape to
           // be hit, so it listens to the whole game view (anywhere inside the camera frame).
@@ -433,31 +440,65 @@ export class BehaviorSystem implements System {
 
   /**
    * Collision events for this behavior: every pair in which one collider belongs to the
-   * behavior's body (its owner, or itself when it has none) fires once, with `other` being
-   * the body on the far side.
+   * behavior's body (its owner, or itself when it has none) fires, with `other` being the body on
+   * the far side – enter and exit once, stay every frame or, with an interval, once each time that
+   * long has passed since the pair met (#149). Each stay node keeps a clock per pair in its node
+   * state, and a pair that is gone takes its clock with it.
    */
-  private fireCollisions(instance: Instance, interpreter: GraphInterpreter, ctx: NodeContext): void {
-    if (!this.collisions) return;
+  private fireCollisions(
+    instance: Instance,
+    interpreter: GraphInterpreter,
+    ctx: NodeContext,
+    dt: number,
+  ): void {
+    const collisions = this.collisions;
+    if (!collisions) return;
     const body = instance.entity.parent ?? instance.entity;
-    const fire = (type: string, pairs: CollisionPair[], contact = false) => {
-      for (const { a, b, normal, impulse } of pairs) {
-        const own = bodyOf(a) === body ? a : bodyOf(b) === body ? b : null;
-        if (!own) continue;
-        const other = own === a ? b : a;
-        const outputs: Record<string, Value> = { other: bodyOf(other), otherCollider: other, collider: own };
-        if (contact) {
-          // The pair's normal points towards `a`; seen from `b` it points the other way.
-          const sign = own === a ? 1 : -1;
-          outputs.normalX = sign * (normal?.x ?? 0) || 0;
-          outputs.normalY = sign * (normal?.y ?? 0) || 0;
-          outputs.impulse = impulse ?? 0;
-        }
-        interpreter.fire(type, ctx, outputs);
+    const mine = (pairs: CollisionPair[]) =>
+      pairs.flatMap((pair) => {
+        const own = bodyOf(pair.a) === body ? pair.a : bodyOf(pair.b) === body ? pair.b : null;
+        return own ? [{ pair, own, other: own === pair.a ? pair.b : pair.a }] : [];
+      });
+    const outputsOf = ({ own, other, pair }: Side, contact?: Partial<Contact> | null) => {
+      const outputs: Record<string, Value> = { other: bodyOf(other), otherCollider: other, collider: own };
+      if (contact !== undefined) {
+        // The pair's normal points towards `a`; seen from `b` it points the other way.
+        const sign = own === pair.a ? 1 : -1;
+        outputs.normalX = sign * (contact?.normal?.x ?? 0) || 0;
+        outputs.normalY = sign * (contact?.normal?.y ?? 0) || 0;
+        outputs.impulse = contact?.impulse ?? 0;
+        outputs.pointX = contact?.point?.x ?? 0;
+        outputs.pointY = contact?.point?.y ?? 0;
       }
+      return outputs;
     };
-    fire('OnCollisionEnter', this.collisions.enters, true);
-    fire('OnCollisionStay', this.collisions.stays);
-    fire('OnCollisionExit', this.collisions.exits);
+    for (const side of mine(collisions.enters))
+      interpreter.fire('OnCollisionEnter', ctx, outputsOf(side, side.pair));
+    const stays = mine(collisions.stays);
+    const contacts = new Map<CollisionPair, Contact | null>();
+    const contactOf = (pair: CollisionPair) => {
+      if (!contacts.has(pair)) contacts.set(pair, collisions.contactOf(pair));
+      return contacts.get(pair)!;
+    };
+    for (const node of interpreter.eventNodes('OnCollisionStay')) {
+      const interval = Math.max(0, Number(node.params.interval ?? 0)) || 0;
+      const clocks = interpreter.nodeState.get(node.id) ?? {};
+      const running: Record<string, number> = {};
+      for (const side of stays) {
+        let fires = 1;
+        if (interval > 0) {
+          const key = `${side.pair.a.id}|${side.pair.b.id}`;
+          let elapsed = (clocks[key] ?? 0) + dt;
+          for (fires = 0; elapsed >= interval - 1e-9; fires++) elapsed -= interval;
+          running[key] = elapsed;
+        }
+        for (let i = 0; i < fires; i++)
+          interpreter.fire('OnCollisionStay', ctx, outputsOf(side, contactOf(side.pair)), (n) => n === node);
+      }
+      if (interval > 0) interpreter.nodeState.set(node.id, running);
+      else interpreter.nodeState.delete(node.id);
+    }
+    for (const side of mine(collisions.exits)) interpreter.fire('OnCollisionExit', ctx, outputsOf(side));
   }
 
   /**
@@ -569,6 +610,18 @@ export class BehaviorSystem implements System {
         found.y += dy;
         return NOT_BLOCKED;
       },
+      raycast: (from, direction, length, { ignore, triggers }) => {
+        const hit = this.collisions?.raycast(world, from, direction, length, {
+          ignore: resolve(ignore) ?? null,
+          triggers,
+        });
+        world.noteRay(from, hit?.point ?? pointAlong(from, direction, length), Boolean(hit));
+        return hit ? { ...hit, object: bodyOf(hit.collider) } : null;
+      },
+      ignoreOneWay: (target, seconds) => {
+        const found = resolve(target);
+        if (found) world.ignoreOneWay(found, seconds);
+      },
       physics:
         this.collisions instanceof PhysicsSystem
           ? physicsControl(world, this.collisions, resolve)
@@ -608,6 +661,13 @@ export class BehaviorSystem implements System {
   }
 }
 
+/** Where a ray of that length ends; where it has no direction, where it starts. */
+function pointAlong(from: Vec2, direction: Vec2, length: number): Vec2 {
+  const d = Math.hypot(direction.x, direction.y);
+  if (!(d > 0) || !(length > 0)) return from;
+  return { x: from.x + (direction.x / d) * length, y: from.y + (direction.y / d) * length };
+}
+
 /** The physics nodes' way into the played game's engine, with the handles of the graph resolved. */
 function physicsControl(
   world: World,

src/runtime/systems/CollisionSystem.ts

@@ -2,13 +2,17 @@ import { isHandleEnabled } from '../../core/graph';
 import { shapesOverlap } from '../../core/properties/collider';
 import type { Entity } from '../Entity';
 import type { World } from '../World';
+import type { Vec2 } from '../../core/model/Properties';
 import {
   bodyOf,
+  type Contact,
   type CollisionPair,
   type CollisionSource,
   isCollisionBody,
   type MoveResult,
   partsOf,
+  type RayFilter,
+  type RayResult,
   Solids,
 } from './solids';
 import type { System } from './System';
@@ -78,4 +82,13 @@ export class CollisionSystem implements System, CollisionSource {
   moveAndSlide(world: World, entity: Entity, dx: number, dy: number): MoveResult {
     return this.solids.moveAndSlide(world, entity, dx, dy);
   }
+
+  raycast(world: World, from: Vec2, direction: Vec2, length: number, filter: RayFilter): RayResult | null {
+    return this.solids.raycast(world, from, direction, length, filter);
+  }
+
+  /** Nothing is simulated here, so a contact has no normal or impulse to tell. */
+  contactOf(): Contact | null {
+    return null;
+  }
 }

src/runtime/systems/solids.ts

@@ -17,9 +17,14 @@ import {
   contactBetween,
   exitDistance,
   isTrigger,
+  landsOn,
+  movedShape,
+  oneWayFacing,
   overlapDepth,
   shapeExtent,
+  shapesOverlap,
 } from '../../core/properties/collider';
+import { rayCast } from '../../core/properties/ray';
 import { colliderMaterial } from '../../core/properties/rigidbody';
 import type { Entity } from '../Entity';
 import type { World } from '../World';
@@ -36,14 +41,15 @@ const SQUARE = 1e-6;
 /**
  * Two bodies that overlap (or overlapped) – always the same pair order per key. Either side is a
  * collider or a placed tilemap, which takes part as a whole with its solid cells (#132).
- * `normal` points from `b` towards `a` and `impulse` is how hard they met; both are only known
- * where the physics engine saw the contact begin (#146), and zero elsewhere.
+ * `normal` points from `b` towards `a`, `impulse` is how hard they met and `point` where; they are
+ * only known where the physics engine saw the contact begin (#146), and zero elsewhere.
  */
 export interface CollisionPair {
   a: Entity;
   b: Entity;
   normal?: Vec2;
   impulse?: number;
+  point?: Vec2;
 }
 
 /**
@@ -75,14 +81,36 @@ export const NOT_BLOCKED: MoveResult = Object.freeze({
   normal: Object.freeze({ x: 0, y: 0 }),
 });
 
-/** A shape in the mover's way and the collider or tilemap it belongs to. */
-interface Obstacle {
+/**
+ * A shape of a collider or tilemap, and for a one-way one the world direction it blocks from (#155):
+ * only a contact whose normal lies within 45° of it stops anything.
+ */
+export interface SolidShape {
   shape: ColliderShape;
+  facing: Vec2 | null;
+}
+
+/** A shape in the mover's way and the collider or tilemap it belongs to. */
+interface Obstacle extends SolidShape {
   body: Entity;
 }
 
+/** What a ray met (#153): the collider or tilemap, where, the face's normal and how far along the ray. */
+export interface RayResult {
+  collider: Entity;
+  point: Vec2;
+  normal: Vec2;
+  distance: number;
+}
+
+/** Which colliders a ray looks at: all but those of `ignore` and below it, triggers only when asked. */
+export interface RayFilter {
+  ignore: Entity | null;
+  triggers: boolean;
+}
+
 /** Where a sweep stopped: what it met, with which own collider, the normal, and the move left over. */
-interface Contact {
+interface SweepContact {
   by: Entity;
   own: Entity;
   normal: Vec2;
@@ -96,6 +124,20 @@ export interface CollisionSource {
   readonly exits: CollisionPair[];
   touching(world: World, a: Entity, b: Entity): boolean;
   moveAndSlide(world: World, entity: Entity, dx: number, dy: number): MoveResult;
+  raycast(world: World, from: Vec2, direction: Vec2, length: number, filter: RayFilter): RayResult | null;
+  /**
+   * How a pair that stays in contact touches right now (#149): the normal from `b` towards `a`, the
+   * impulse of the last physics step and the middle of the contact points; null where nothing
+   * simulates the contact (the editor run).
+   */
+  contactOf(pair: CollisionPair): Contact | null;
+}
+
+/** A contact as the physics engine knows it (see `CollisionSource.contactOf`). */
+export interface Contact {
+  normal: Vec2;
+  impulse: number;
+  point: Vec2;
 }
 
 /**
@@ -108,23 +150,27 @@ export class Solids {
    * painting, or a behavior changing the map, is picked up by the next one – and turned into world
    * shapes only when asked, since the map may move in between.
    */
-  private blocks = new Map<Entity, { rects: CellRect[]; polygons: CellPolygon[] }>();
+  private blocks = new Map<Entity, TilemapBlocks>();
 
   /** Forgets the cells, so the next tick works them out afresh. */
   reset(): void {
     this.blocks = new Map();
   }
 
-  private blocksOf(world: World, tilemap: Entity): { rects: CellRect[]; polygons: CellPolygon[] } {
+  private blocksOf(world: World, tilemap: Entity): TilemapBlocks {
     let blocks = this.blocks.get(tilemap);
     if (!blocks) {
       const asset = findAssetOf(world.project, tilemap.assetId, 'tilemap');
+      const { project } = world;
+      const { props } = tilemap;
       blocks = asset
         ? {
-            rects: solidRects(world.project, tilemap.props, asset),
-            polygons: solidPolygons(world.project, tilemap.props, asset),
+            rects: solidRects(project, props, asset),
+            polygons: solidPolygons(project, props, asset),
+            oneWayRects: solidRects(project, props, asset, true),
+            oneWayPolygons: solidPolygons(project, props, asset, true),
           }
-        : { rects: [], polygons: [] };
+        : { rects: [], polygons: [], oneWayRects: [], oneWayPolygons: [] };
       this.blocks.set(tilemap, blocks);
     }
     return blocks;
@@ -132,17 +178,48 @@ export class Solids {
 
   /**
    * The shapes a body occupies in the world: one for a collider; for a tilemap one box per merged
-   * rectangle and one polygon per outlined cell (#141). A tilemap placed before the first tick is
-   * worked out on the spot.
+   * rectangle and one polygon per outlined cell (#141), the one-way cells blocking from the map's
+   * top (#155). A tilemap placed before the first tick is worked out on the spot.
    */
-  shapesOf(world: World, body: Entity): ColliderShape[] {
-    if (body.type !== 'tilemap') return [shapeOf(body)];
+  solidShapesOf(world: World, body: Entity): SolidShape[] {
     const m = worldMatrixOf(body);
-    const { rects, polygons } = this.blocksOf(world, body);
-    return [
-      ...rects.map((rect) => cellRectShape(body.props, rect, m)),
-      ...polygons.map((polygon) => cellPolygonShape(body.props, polygon, m)),
+    if (body.type !== 'tilemap')
+      return [{ shape: colliderShape(body.props, m), facing: oneWayFacing(body.props, m) }];
+    const { rects, polygons, oneWayRects, oneWayPolygons } = this.blocksOf(world, body);
+    const up = oneWayFacing({ oneWay: true }, m);
+    const shapes = (cells: CellRect[], outlines: CellPolygon[], facing: Vec2 | null) => [
+      ...cells.map((rect) => ({ shape: cellRectShape(body.props, rect, m), facing })),
+      ...outlines.map((polygon) => ({ shape: cellPolygonShape(body.props, polygon, m), facing })),
     ];
+    return [...shapes(rects, polygons, null), ...shapes(oneWayRects, oneWayPolygons, up)];
+  }
+
+  shapesOf(world: World, body: Entity): ColliderShape[] {
+    return this.solidShapesOf(world, body).map(({ shape }) => shape);
+  }
+
+  /**
+   * The first solid the ray from `from` along `direction` meets within `length` (world units): any
+   * blocking collider or tilemap cell, triggers when asked, a one-way one only on the side it blocks
+   * from. What the ray starts inside is not met (see `rayCast`).
+   */
+  raycast(world: World, from: Vec2, direction: Vec2, length: number, filter: RayFilter): RayResult | null {
+    const d = unitOf(direction);
+    if ((d.x === 0 && d.y === 0) || !(length > 0)) return null;
+    let best: RayResult | null = null;
+    for (const body of world.entities) {
+      if (!isCollisionBody(body) || !isHandleEnabled(body)) continue;
+      if (body.type === 'collider' && isTrigger(body.props) && !filter.triggers) continue;
+      if (filter.ignore && travelsWith(body, filter.ignore)) continue;
+      for (const { shape, facing } of this.solidShapesOf(world, body)) {
+        const hit = rayCast(shape, from, d, best?.distance ?? length);
+        if (!hit || (facing && !landsOn(hit.normal, facing))) continue;
+        if (best && hit.distance >= best.distance) continue;
+        const point = { x: from.x + d.x * hit.distance, y: from.y + d.y * hit.distance };
+        best = { collider: body, point, normal: hit.normal, distance: hit.distance };
+      }
+    }
+    return best;
   }
 
   /**
@@ -170,13 +247,19 @@ export class Solids {
       return NOT_BLOCKED;
     }
     // Nothing that blocks moves while this one does, so its shapes are taken once for the whole move.
-    const obstacles = world.entities
+    const obstacles: Obstacle[] = world.entities
       .filter((c) => blocksMover(c, entity))
-      .flatMap((body) => this.shapesOf(world, body).map((shape) => ({ shape, body })));
-    const contacts: Contact[] = [];
+      .flatMap((body) => this.solidShapesOf(world, body).map((solid) => ({ ...solid, body })));
+    // A one-way solid the mover is inside already, or told to fall through, lets it pass for the
+    // whole move: it is on its way through, from below or from the side.
+    const ignoring = world.ignoresOneWay(entity);
+    const passing = new Set(
+      obstacles.filter((o) => o.facing && (ignoring || own.some((a) => shapesOverlap(shapeOf(a), o.shape)))),
+    );
+    const contacts: SweepContact[] = [];
     let rest = wanted;
     for (let pass = 0; pass < MAX_PASSES && (rest.x !== 0 || rest.y !== 0); pass++) {
-      const contact = sweep(entity, frame, own, obstacles, rest);
+      const contact = sweep(entity, frame, own, obstacles, passing, rest);
       if (!contact) break;
       contacts.push(contact);
       rest = slideAlong(contact.left, contact.normal, frictionBetween(contact.own, contact.by));
@@ -213,8 +296,16 @@ function parentFrame(entity: Entity): Mat {
 /**
  * Moves the entity along `move` (world) in steps no solid is thinner than, until a step runs into
  * one: then it is set back flush against it and the contact is reported with what is left of the move.
+ * A one-way solid met anywhere but on its blocking side joins `passing` instead.
  */
-function sweep(entity: Entity, frame: Mat, own: Entity[], obstacles: Obstacle[], move: Vec2): Contact | null {
+function sweep(
+  entity: Entity,
+  frame: Mat,
+  own: Entity[],
+  obstacles: Obstacle[],
+  passing: Set<Obstacle>,
+  move: Vec2,
+): SweepContact | null {
   const distance = Math.hypot(move.x, move.y);
   const forward = { x: move.x / distance, y: move.y / distance };
   const steps = Math.min(MAX_STEPS, Math.max(1, Math.ceil(distance / stepLimit(own, obstacles, forward))));
@@ -238,6 +329,7 @@ function sweep(entity: Entity, frame: Mat, own: Entity[], obstacles: Obstacle[],
     for (const [k, a] of own.entries()) {
       const mover = shapeOf(a);
       for (const [j, obstacle] of obstacles.entries()) {
+        if (passing.has(obstacle)) continue;
         const was = before[k]![j]!;
         if (overlapDepth(contactBetween(mover, obstacle.shape, forward).separation) <= was + DEEPER) continue;
         // Coming from outside, the step goes back exactly to where the two met; from inside, all
@@ -246,6 +338,13 @@ function sweep(entity: Entity, frame: Mat, own: Entity[], obstacles: Obstacle[],
           was === 0
             ? Math.min(step, exitDistance(mover, obstacle.shape, { x: -forward.x, y: -forward.y }))
             : step;
+        if (obstacle.facing) {
+          const met = movedShape(mover, (p) => ({ x: p.x - forward.x * back, y: p.y - forward.y * back }), 0);
+          if (!landsOn(contactBetween(met, obstacle.shape, forward).normal, obstacle.facing)) {
+            passing.add(obstacle);
+            continue;
+          }
+        }
         if (back > correction || !found) {
           correction = back;
           found = { own: a, obstacle };
@@ -299,6 +398,13 @@ function unitOf(v: Vec2): Vec2 {
   return length > 0 ? { x: v.x / length, y: v.y / length } : v;
 }
 
+interface TilemapBlocks {
+  rects: CellRect[];
+  polygons: CellPolygon[];
+  oneWayRects: CellRect[];
+  oneWayPolygons: CellPolygon[];
+}
+
 export function shapeOf(collider: Entity): ColliderShape {
   return colliderShape(collider.props, worldMatrixOf(collider));
 }