jumpstorm/engine/systems/Collision.ts

220 lines
6.4 KiB
TypeScript

import { SystemNames, System } from ".";
import {
Mass,
BoundingBox,
ComponentNames,
Jump,
Velocity,
Forces,
} from "../components";
import { Game } from "../Game";
import { PhysicsConstants } from "../config";
import { Entity } from "../entities";
import type { Dimension2D, Velocity2D } from "../interfaces";
import { QuadTree } from "../structures";
export class Collision extends System {
private static readonly COLLIDABLE_COMPONENT_NAMES = [
ComponentNames.Collide,
ComponentNames.TopCollidable,
];
private static readonly QUADTREE_MAX_LEVELS = 10;
private static readonly QUADTREE_SPLIT_THRESHOLD = 10;
private quadTree: QuadTree;
constructor(screenDimensions: Dimension2D) {
super(SystemNames.Collision);
this.quadTree = new QuadTree(
{ x: 0, y: 0 },
screenDimensions,
Collision.QUADTREE_MAX_LEVELS,
Collision.QUADTREE_SPLIT_THRESHOLD,
);
}
public update(_dt: number, game: Game) {
// rebuild the quadtree
this.quadTree.clear();
const entitiesToAddToQuadtree: Entity[] = [];
Collision.COLLIDABLE_COMPONENT_NAMES.map((componentName) =>
game.componentEntities.get(componentName),
).forEach(
(entityIds?: Set<number>) =>
entityIds?.forEach((id) => {
const entity = game.entities.get(id);
if (!entity || !entity.hasComponent(ComponentNames.BoundingBox)) {
return;
}
entitiesToAddToQuadtree.push(entity);
}),
);
entitiesToAddToQuadtree.forEach((entity) => {
const boundingBox = entity.getComponent<BoundingBox>(
ComponentNames.BoundingBox,
);
let dimension = { ...boundingBox.dimension };
if (boundingBox.rotation != 0) {
dimension = boundingBox.getOutscribedBoxDims();
}
this.quadTree.insert({
id: entity.id,
dimension,
center: boundingBox.center,
});
});
// find colliding entities and perform collisions
const collidingEntities = this.getCollidingEntities(
entitiesToAddToQuadtree,
game,
);
collidingEntities.forEach(([entityAId, entityBId]) => {
const [entityA, entityB] = [entityAId, entityBId].map((id) =>
game.entities.get(id),
);
if (entityA && entityB) {
this.performCollision(entityA, entityB);
}
});
}
private performCollision(entityA: Entity, entityB: Entity) {
const [entityABoundingBox, entityBBoundingBox] = [entityA, entityB].map(
(entity) => entity.getComponent<BoundingBox>(ComponentNames.BoundingBox),
);
let velocity: Velocity2D = { dCartesian: { dx: 0, dy: 0 }, dTheta: 0 };
if (entityA.hasComponent(ComponentNames.Velocity)) {
velocity = entityA.getComponent<Velocity>(
ComponentNames.Velocity,
).velocity;
}
if (
entityA.hasComponent(ComponentNames.Collide) &&
entityB.hasComponent(ComponentNames.TopCollidable) &&
entityABoundingBox.center.y <= entityBBoundingBox.center.y &&
velocity.dCartesian.dy >= 0 // don't apply "floor" logic when coming through the bottom
) {
if (entityBBoundingBox.rotation != 0) {
throw new Error(
`entity with id ${entityB.id} has TopCollidable component and a non-zero rotation. that is not (yet) supported.`,
);
}
// remove previous velocity in the y axis
if (velocity) velocity.dCartesian.dy = 0;
// apply normal force
if (entityA.hasComponent(ComponentNames.Gravity)) {
const mass = entityA.getComponent<Mass>(ComponentNames.Mass).mass;
const F_n = -mass * PhysicsConstants.GRAVITY;
entityA.getComponent<Forces>(ComponentNames.Forces).forces.push({
fCartesian: { fy: F_n, fx: 0 },
torque: 0,
});
}
// reset the entities' jump
if (entityA.hasComponent(ComponentNames.Jump)) {
entityA.getComponent<Jump>(ComponentNames.Jump).canJump = true;
}
entityABoundingBox.center.y =
entityBBoundingBox.center.y -
entityBBoundingBox.dimension.height / 2 -
this.getDyToPushOutOfFloor(entityABoundingBox, entityBBoundingBox);
}
}
private getCollidingEntities(
collidableEntities: Entity[],
game: Game,
): [number, number][] {
const collidingEntityIds: [number, number][] = [];
for (const entity of collidableEntities) {
const boundingBox = entity.getComponent<BoundingBox>(
ComponentNames.BoundingBox,
);
const neighborIds = this.quadTree
.getNeighborIds({
id: entity.id,
dimension: boundingBox.dimension,
center: boundingBox.center,
})
.filter((neighborId) => neighborId != entity.id);
neighborIds.forEach((neighborId) => {
const neighbor = game.getEntity(neighborId);
if (!neighbor) return;
const neighborBoundingBox = neighbor.getComponent<BoundingBox>(
ComponentNames.BoundingBox,
);
if (boundingBox.isCollidingWith(neighborBoundingBox)) {
collidingEntityIds.push([entity.id, neighborId]);
}
});
}
return collidingEntityIds;
}
// ramblings: https://excalidraw.com/#json=z-xD86Za4a3duZuV2Oky0,KaGe-5iHJu1Si8inEo4GLQ
private getDyToPushOutOfFloor(
entityBoundingBox: BoundingBox,
floorBoundingBox: BoundingBox,
): number {
const {
dimension: { width, height },
center: { x },
} = entityBoundingBox;
const outScribedRectangle = entityBoundingBox.getOutscribedBoxDims();
let rads = entityBoundingBox.getRotationInPiOfUnitCircle();
let dx = (width * Math.cos(rads) - height * Math.sin(rads)) / 2;
if (rads >= Math.PI / 2) {
rads -= Math.PI / 2;
dx = (height * Math.cos(rads) - width * Math.sin(rads)) / 2;
}
const clippedX = x + dx; // x coordinate of the vertex below the surface (if existant)
let boundedCollisionX = 0; // bounded x on the surface from width
if (x >= floorBoundingBox.center.x) {
boundedCollisionX = Math.min(
floorBoundingBox.center.x + floorBoundingBox.dimension.width / 2,
clippedX,
);
return (
outScribedRectangle.height / 2 -
Math.max((clippedX - boundedCollisionX) * Math.tan(rads), 0)
);
}
boundedCollisionX = Math.max(
floorBoundingBox.center.x - floorBoundingBox.dimension.width / 2,
clippedX,
);
return (
outScribedRectangle.height / 2 -
Math.max((boundedCollisionX - clippedX) * Math.tan(Math.PI / 2 - rads), 0)
);
}
}