sys_physics_integrate

The first step of the physics simulation: integrate the rigid body's acceleration and velocity, and update the entity's transform.

import {Vec2} from "../../lib/math.js"; import {vec2_add, vec2_scale, vec2_set} from "../../lib/vec2.js"; import {Entity} from "../../lib/world.js"; import {RigidKind} from "../components/com_rigid_body2d.js"; import {Game} from "../game.js"; import {Has} from "../world.js";

export function sys_physics2d_integrate(game: Game, delta: number) { for (let ent = 0; ent < game.World.Signature.length; ent++) { if ((game.World.Signature[ent] & QUERY) === QUERY) { update(game, ent, delta); } } }

function update(game: Game, entity: Entity, delta: number) { let local = game.World.LocalTransform2D[entity]; let rigid_body = game.World.RigidBody2D[entity]; if (rigid_body.Kind === RigidKind.Dynamic) { // Compute change to velocity due to the gravity. rigid_body.VelocityLinear[1] += GRAVITY * delta; // Compute change to velocity due to external forces. vec2_scale(rigid_body.Acceleration, rigid_body.Acceleration, delta); vec2_add(rigid_body.VelocityLinear, rigid_body.VelocityLinear, rigid_body.Acceleration); // Compute and apply drag. vec2_scale(velocity_drag, rigid_body.VelocityLinear, -rigid_body.Drag); vec2_add(rigid_body.VelocityLinear, rigid_body.VelocityLinear, velocity_drag); // Apply velocity to position. vec2_scale(velocity_delta, rigid_body.VelocityLinear, delta); vec2_add(local.Translation, local.Translation, velocity_delta); local.Rotation += rigid_body.VelocityAngular * delta; game.World.Signature[entity] |= Has.Dirty; // Reset force/acceleration. vec2_set(rigid_body.Acceleration, 0, 0); } }