sys_physics_kinematic

Derive the velocity of kinematic rigid bodies from the change in their position.

This allows entities to move by changing their transform directly (e.g. through sys_move) and also take part in the physics simulation, in particular in the collision response step in sys_physics_resolve.

import {mat4_get_translation} from "../../lib/mat4.js"; import {Vec3} from "../../lib/math.js"; import {vec3_copy, vec3_scale, vec3_subtract} from "../../lib/vec3.js"; import {Entity} from "../../lib/world.js"; import {RigidKind} from "../components/com_rigid_body.js"; import {Game} from "../game.js"; import {Has} from "../world.js";

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

function update(game: Game, entity: Entity, delta: number) { let transform = game.World.Transform[entity]; let rigid_body = game.World.RigidBody[entity]; mat4_get_translation(current_position, transform.World); if (rigid_body.Kind === RigidKind.Kinematic) { vec3_subtract(movement_delta, current_position, rigid_body.LastPosition); // Compute velocity from this frame's movement. vec3_scale(rigid_body.VelocityLinear, movement_delta, 1 / delta); } vec3_copy(rigid_body.LastPosition, current_position); }