Improve Collision Detection: More Active w/ Actors

* Improve the collision detection algorithm so that Actor OnCollide
  scripts get called more often WHILE an actor is moving, to prevent a
  fast-moving actor from zipping right through the "solid" hitbox and
  not giving the subject actor time to protest the movement.
* It's implemented by adding a `Settled` boolean to the OnCollide event
  object. When the game is testing out movement, Settled=false to give
  the actor a chance to say "I'm solid!" and have the moving party be
  stopped early.
* After all this is done, for any pair of actors still with overlapping
  hitboxes, OnCollide is called one last time with Settled=true. This is
  when the actor should run its actions (like publishing messages to
  other actors, changing state as in a trapdoor, etc.)
* The new collision detection algorithm works as follows:
  * Stage 1 is the same as before, all mobile actors are moved and
    tested against level geometry. They record their Original and New
    position during this phase.
  * Stage 2 is where we re-run that movement but ping actors being
    intersected each step of the way. We trace the steps between
    Original and New position, test OnCollide handler, and if it returns
    false we move the mobile actor to the Last Good Position along the
    trace.
  * Stage 3 we run the final OnCollide(Settled=true) to let actors run
    actions they wanted to for their collide handler, WITHOUT spamming
    those actions during Stage 2.
* This should now allow for tweaking of gravity speed and player speed
  without breaking all actor collision checking.

dev-assets/doodads/azulian/azulian-red.js

@@ -11,24 +11,16 @@ function main() {
 	Self.AddAnimation("walk-left", 100, ["red-wl1", "red-wl2", "red-wl3", "red-wl4"]);
 	Self.AddAnimation("walk-right", 100, ["red-wr1", "red-wr2", "red-wr3", "red-wr4"]);
 
-	// var nextTurn = time.Add(time.Now(), 2500);
-
 	// Sample our X position every few frames and detect if we've hit a solid wall.
 	var sampleTick = 0;
 	var sampleRate = 5;
 	var lastSampledX = 0;
 
 	setInterval(function() {
-		// if (time.Now().After(nextTurn)) {
-		// 	direction = direction === "right" ? "left" : "right";
-		// 	nextTurn = time.Add(time.Now(), 2500);
-		// }
-
 		if (sampleTick % sampleRate === 0) {
 			var curX = Self.Position().X;
 			var delta = Math.abs(curX - lastSampledX);
 			if (delta < 5) {
-				log.Error("flip red azulian");
 				direction = direction === "right" ? "left" : "right";
 			}
 			lastSampledX = curX;

dev-assets/doodads/buttons/button.js

@@ -4,6 +4,10 @@ function main() {
 	var timer = 0;
 
 	Events.OnCollide(function(e) {
+		if (!e.Settled) {
+			return;
+		}
+
 		// Verify they've touched the button.
 		if (e.Overlap.Y + e.Overlap.H < 24) {
 			return;

dev-assets/doodads/buttons/sticky.js

@@ -13,6 +13,10 @@ function main() {
 	})
 
 	Events.OnCollide(function(e) {
+		if (!e.Settled) {
+			return;
+		}
+
 		if (pressed) {
 			return;
 		}

dev-assets/doodads/doors/electric-door.js

@@ -37,11 +37,4 @@ function main() {
 			}
 		}
 	});
-	Events.OnLeave(function() {
-		// if (opened) {
-		// 	Self.PlayAnimation("close", function() {
-		// 		opened = false;
-		// 	});
-		// }
-	})
 }

dev-assets/doodads/doors/locked-door.js

@@ -2,8 +2,6 @@ function main() {
 	Self.AddAnimation("open", 0, [1]);
 	var unlocked = false;
 
-	// Self.Canvas.SetBackground(RGBA(0, 255, 255, 100));
-
 	// Map our door names to key names.
 	var KeyMap = {
 		"Blue Door": "Blue Key",
@@ -12,8 +10,6 @@ function main() {
 		"Yellow Door": "Yellow Key"
 	}
 
-	// log.Warn("%s loaded!", Self.Doodad.Title);
-	// console.log("%s Setting hitbox", Self.Doodad.Title);
 	Self.SetHitbox(16, 0, 32, 64);
 
 	Events.OnCollide(function(e) {
@@ -28,11 +24,10 @@ function main() {
 				return false;
 			}
 
+			if (e.Settled) {
 				unlocked = true;
 				Self.PlayAnimation("open", null);
 			}
+		}
 	});
-	// Events.OnLeave(function(e) {
-	// 	console.log("%s has stopped touching %s", e, Self.Doodad.Title)
-	// })
 }

dev-assets/doodads/switches/switch.js

@@ -14,6 +14,10 @@ function main() {
 	});
 
 	Events.OnCollide(function(e) {
+		if (!e.Settled) {
+			return;
+		}
+
 		if (collide === false) {
 			state = !state;
 			Message.Publish("power", state);

dev-assets/doodads/trapdoors/trapdoor.js

@@ -18,11 +18,11 @@ function main() {
 	if (direction === "left") {
 		Self.SetHitbox(48, 0, doodadSize, doodadSize);
 	} else if (direction === "right") {
-		Self.SetHitbox(0, 0, thickness+4, doodadSize);
+		Self.SetHitbox(0, 0, thickness, doodadSize);
 	} else if (direction === "up") {
 		Self.SetHitbox(0, doodadSize - thickness, doodadSize, doodadSize);
 	} else { // Down, default.
-		Self.SetHitbox(0, 0, 72, 6);
+		Self.SetHitbox(0, 0, doodadSize, thickness);
 	}
 
 	var animationSpeed = 100;
@@ -46,18 +46,43 @@ function main() {
 		// Is the actor colliding our solid part?
 		if (e.InHitbox) {
 			// Are they touching our opening side?
-			if (direction === "left" && (e.Overlap.X+e.Overlap.W) < (doodadSize-thickness)) {
+			if (direction === "left") {
+				if (doodadSize - e.Overlap.X < thickness) {
+					// Touching the right edge, open the door.
+					opened = true;
+					Self.PlayAnimation("open", null);
+					return;
+				}
+				if (e.Overlap.W === doodadSize - thickness) {
 					return false;
-			} else if (direction === "right" && e.Overlap.X > 0) {
+				}
+			} else if (direction === "right") {
+				if (e.Overlap.X > 0) {
 					return false;
-			} else if (direction === "up" && (e.Overlap.Y+e.Overlap.H) < doodadSize) {
-				return false;
-			} else if (direction === "down" && e.Overlap.Y > 0) {
-				return false;
-			} else {
+				} else if (e.Settled) {
 					opened = true;
 					Self.PlayAnimation("open", null);
 				}
+			} else if (direction === "up") {
+				if (doodadSize - e.Overlap.Y < thickness) {
+					// Touching the bottom edge, open the door.
+					opened = true;
+					Self.PlayAnimation("open", null);
+					return;
+				}
+				if (e.Overlap.H === doodadSize - thickness) {
+					return false;
+				}
+			} else if (direction === "down") {
+				if (e.Overlap.Y > 0) {
+					return false;
+				} else if (e.Settled) {
+					opened = true;
+					Self.PlayAnimation("open", null);
+				}
+			}
+
+			return true;
 		}
 	});
 

pkg/balance/boolprops.go

@@ -17,6 +17,9 @@ var (
 
 	// Pretty-print JSON files when writing.
 	JSONIndent bool
+
+	// Temporary debug flag.
+	TempDebug bool
 )
 
 // Human friendly names for the boolProps. Not necessarily the long descriptive
@@ -25,6 +28,7 @@ var props = map[string]*bool{
 	"showAllDoodads":    &ShowHiddenDoodads,
 	"writeLockOverride": &WriteLockOverride,
 	"prettyJSON":        &JSONIndent,
+	"tempDebug":         &TempDebug,
 
 	// WARNING: SLOW!
 	"disableChunkTextureCache": &DisableChunkTextureCache,

pkg/collision/actors_test.go

@@ -101,11 +101,19 @@ func TestActorCollision(t *testing.T) {
 		case 0:
 			assert(i, overlap, 0, 1)
 		case 1:
-			assert(i, overlap, 3, 4)
+			assert(i, overlap, 1, 0)
 		case 2:
-			assert(i, overlap, 5, 6)
+			assert(i, overlap, 3, 4)
 		case 3:
+			assert(i, overlap, 4, 3)
+		case 4:
+			assert(i, overlap, 5, 6)
+		case 5:
 			assert(i, overlap, 5, 7)
+		case 6:
+			assert(i, overlap, 6, 5)
+		case 7:
+			assert(i, overlap, 7, 5)
 		default:
 			t.Errorf("got unexpected collision result, index %d, tuple (%d,%d)",
 				i, a, b,

pkg/collision/collide_actors.go

@@ -31,8 +31,10 @@ func BetweenBoxes(boxes []render.Rect) chan BoxCollision {
 	go func() {
 		// Outer loop: test each box for intersection with the others.
 		for i, box := range boxes {
-			for j := i + 1; j < len(boxes); j++ {
-				other := boxes[j]
+			for j, other := range boxes {
+				if i == j {
+					continue
+				}
 				collision, err := CompareBoxes(box, other)
 				if err == nil {
 					collision.A = i

pkg/scripting/pubsub.go

@@ -35,7 +35,6 @@ func RegisterPublishHooks(vm *VM) {
 	// Register the Message.Subscribe and Message.Publish functions.
 	vm.vm.Set("Message", map[string]interface{}{
 		"Subscribe": func(name string, callback otto.Value) {
-			log.Error("SUBSCRIBE: %s", name)
 			if !callback.IsFunction() {
 				log.Error("SUBSCRIBE(%s): callback is not a function", name)
 				return

pkg/scripting/vm.go

@@ -73,6 +73,9 @@ func (vm *VM) RegisterLevelHooks() error {
 		"Point":  render.NewPoint,
 		"Self":   vm.Self, // i.e., the uix.Actor object
 		"Events": vm.Events,
+		"GetTick": func() uint64 {
+			return shmem.Tick
+		},
 
 		"TypeOf": reflect.TypeOf,
 		"time": map[string]interface{}{

pkg/uix/actor_collision.go

@@ -100,26 +100,31 @@ func (w *Canvas) loopActorCollision() error {
 		a, b := w.actors[tuple.A], w.actors[tuple.B]
 		collidingActors[a.ID()] = b.ID()
 
-		// Call the OnCollide handler.
+		// Call the OnCollide handler for A informing them of B's intersection.
 		if w.scripting != nil {
-			// Tell actor A about the collision with B.
-			if err := w.scripting.To(a.ID()).Events.RunCollide(&CollideEvent{
-				Actor:    b,
-				Overlap:  tuple.Overlap,
-				InHitbox: tuple.Overlap.Intersects(a.Hitbox()),
-			}); err != nil {
-				if err == scripting.ErrReturnFalse {
-					if origPoint, ok := originalPositions[b.ID()]; ok {
-						// Trace a vector back from the actor's current position
-						// to where they originated from and find the earliest
-						// point where they are not violating the hitbox.
 			var (
 				rect        = doodads.GetBoundingRect(b)
-							hitbox = a.Hitbox()
+				lastGoodBox = boxes[tuple.B] // worst case scenario we get blocked right away
 			)
+
+			// Firstly we want to make sure B isn't able to clip through A's
+			// solid hitbox if A protests the movement. Trace a vector from
+			// B's original position to their current one and ping A's
+			// OnCollide handler for each step, with Settled=false. A should
+			// only return false if it protests the movement, but not trigger
+			// any actions (such as emit messages to linked doodads) until
+			// Settled=true.
+			if origPoint, ok := originalPositions[b.ID()]; ok {
+				// Trace a vector back from the actor's current position
+				// to where they originated from. If A protests B's position at
+				// ANY time, we mark didProtest=true and continue backscanning
+				// B's movement. The next time A does NOT protest, that is to be
+				// B's new position.
+
+				var firstPoint = true
 				for point := range render.IterLine(
-							b.Position(),
 					origPoint,
+					b.Position(),
 				) {
 					test := render.Rect{
 						X: point.X,
@@ -127,15 +132,40 @@ func (w *Canvas) loopActorCollision() error {
 						W: rect.W,
 						H: rect.H,
 					}
-							info, err := collision.CompareBoxes(
-								boxes[tuple.A],
-								test,
-							)
-							if err != nil || !info.Overlap.Intersects(hitbox) {
-								b.MoveTo(point)
+
+					if info, err := collision.CompareBoxes(boxes[tuple.A], test); err == nil {
+						// B is overlapping A's box, call its OnCollide handler
+						// with Settled=false and see if it protests the overlap.
+						err := w.scripting.To(a.ID()).Events.RunCollide(&CollideEvent{
+							Actor:    b,
+							Overlap:  info.Overlap,
+							InHitbox: info.Overlap.Intersects(a.Hitbox()),
+							Settled:  false,
+						})
+
+						// Did A protest?
+						if err == scripting.ErrReturnFalse {
 							break
+						} else {
+							lastGoodBox = test
 						}
 					}
+
+					firstPoint = false
+				}
+
+				// Were we stopped before we even began?
+				if firstPoint {
+					// TODO: undo the effect of gravity this tick. Use case:
+					// the player lands on top of a solid door, and their
+					// movement is blocked the first step by the door. Originally
+					// he'd continue falling, so I had to move him up to stop it,
+					// turns out moving up by the -gravity is exactly the distance
+					// to go. Don't know why.
+					b.MoveBy(render.NewPoint(0, int32(-balance.Gravity)))
+				} else {
+					b.MoveTo(lastGoodBox.Point())
+				}
 			} else {
 				log.Error(
 					"ERROR: Actors %s and %s overlap and the script returned false,"+
@@ -143,7 +173,17 @@ func (w *Canvas) loopActorCollision() error {
 					a.Doodad.Title, b.Doodad.Title, b.Doodad.Title,
 				)
 			}
-				} else {
+
+			// Movement has been settled. Check if B's point is still invading
+			// A's box and call its OnCollide handler one last time in
+			// Settled=true mode so it can run its actions.
+			if info, err := collision.CompareBoxes(boxes[tuple.A], lastGoodBox); err == nil {
+				if err := w.scripting.To(a.ID()).Events.RunCollide(&CollideEvent{
+					Actor:    b,
+					Overlap:  info.Overlap,
+					InHitbox: info.Overlap.Intersects(a.Hitbox()),
+					Settled:  true,
+				}); err != nil && err != scripting.ErrReturnFalse {
 					log.Error(err.Error())
 				}
 			}

pkg/uix/actor_events.go

@@ -7,4 +7,5 @@ type CollideEvent struct {
 	Actor    *Actor
 	Overlap  render.Rect
 	InHitbox bool // If the two elected hitboxes are overlapping
+	Settled  bool // Movement phase finished, actor script can fire actions
 }