refactor: physics

app/ecs-components/forces.js

@@ -1,7 +1,21 @@
 import Component from '@/ecs/component.js';
 
 export default class Forces extends Component {
+  instanceFromSchema() {
+    return class ForcesInstance extends super.instanceFromSchema() {
+      applyForce({x, y}) {
+        this.forceX += x;
+        this.forceY += y;
+      }
+      applyImpulse({x, y}) {
+        this.impulseX += x;
+        this.impulseY += y;
+      }
+    }
+  }
   static properties = {
+    dampingX: {type: 'float32'},
+    dampingY: {type: 'float32'},
     forceX: {type: 'float32'},
     forceY: {type: 'float32'},
     impulseX: {type: 'float32'},

app/ecs-systems/apply-control-movement.js

@@ -1,10 +1,11 @@
 import {System} from '@/ecs/index.js';
+import {normalizeVector} from '@/util/math.js';
 
 export default class ApplyControlMovement extends System {
 
   static get priority() {
     return {
-      before: 'ApplyForces',
+      before: 'IntegratePhysics',
     };
   }
 
@@ -16,8 +17,14 @@ export default class ApplyControlMovement extends System {
   tick() {
     for (const {Controlled, Forces, Speed} of this.select('default')) {
       if (!Controlled.locked) {
-        Forces.impulseX += Speed.speed * (Controlled.moveRight - Controlled.moveLeft);
-        Forces.impulseY += Speed.speed * (Controlled.moveDown - Controlled.moveUp);
+        const movement = normalizeVector({
+          x: (Controlled.moveRight - Controlled.moveLeft),
+          y: (Controlled.moveDown - Controlled.moveUp),
+        });
+        Forces.applyImpulse({
+          x: Speed.speed * movement.x,
+          y: Speed.speed * movement.y,
+        });
       }
     }
   }

app/ecs-systems/calculate-aabbs.js

@@ -4,7 +4,7 @@ export default class CalculateAabbs extends System {
 
   static get priority() {
     return {
-      after: 'ApplyForces',
+      after: 'IntegratePhysics',
     };
   }
 

app/ecs-systems/clamp-positions.js

@@ -4,7 +4,7 @@ export default class ClampPositions extends System {
 
   static get priority() {
     return {
-      after: 'ApplyForces',
+      after: 'IntegratePhysics',
     }
   }
 

app/ecs-systems/integrate-physics.js

@@ -1,6 +1,6 @@
 import {System} from '@/ecs/index.js';
 
-export default class ApplyForces extends System {
+export default class IntegratePhysics extends System {
 
   static queries() {
     return {

app/ecs-systems/reset-forces.js

@@ -12,8 +12,22 @@ export default class ResetForces extends System {
     };
   }
 
-  tick() {
+  tick(elapsed) {
     for (const {Forces} of this.select('default')) {
+      if (0 !== Forces.forceX) {
+        const factorX = Math.pow(1 - Forces.dampingX, elapsed);
+        Forces.forceX *= factorX;
+        if (Math.abs(Forces.forceX) <= 1) {
+          Forces.forceX = 0;
+        }
+      }
+      if (0 !== Forces.forceY) {
+        const factorY = Math.pow(1 - Forces.dampingY, elapsed);
+        Forces.forceY *= factorY;
+        if (Math.abs(Forces.forceY) <= 1) {
+          Forces.forceY = 0;
+        }
+      }
       Forces.impulseX = 0;
       Forces.impulseY = 0;
     }

app/engine.js

@@ -153,7 +153,7 @@ export default class Engine {
     const defaultSystems = [
       'ResetForces',
       'ApplyControlMovement',
-      'ApplyForces',
+      'IntegratePhysics',
       'ClampPositions',
       'PlantGrowth',
       'FollowCamera',

app/util/math.js

@@ -0,0 +1,7 @@
+export function normalizeVector({x, y}) {
+  if (0 === y && 0 === x) {
+    return {x: 0, y: 0};
+  }
+  const k = 1 / Math.sqrt(x * x + y * y);
+  return {x: x * k, y: y * k};
+}