crystal.Movement

Component allowing an entity to move of its own volition. Entities should have at most one Movement component.

Expected usage of this component is to call set_heading every frame in response to player inputs or AI logic. Every frame, the PhysicsSystem:

• Sets the entity’s linear velocity to match the heading and speed of its movement component.
• Sets the rotation of the entity’s Body to match the heading of its movement component.

A nil heading indicates that the entity is standing still. Its velocity will be zero’ed out by the PhysicsSystem.

Disabling a movement component makes it relinquish control of the entity’s velocity.

Entities using this component should have a Body with the dynamic or kinematic body type.

Constructor

Like all other components, Movement components are created by calling Entity:add_component. This constructor takes one optional number parameter initializing movement speed. Its default value is 10 pixels / s.

local movement_speed = 20; -- pixels / s
entity:add_component(crystal.Movement, movement_speed);

Methods

Name	Description
disable_movement	Prevents this component from affecting entity physics.
enable_movement	Allows this component to affect entity physics.
heading	Returns the direction this entity is attempting to move towards.
is_movement_enabled	Returns whether this movement component is currently enabled.
set_heading	Sets the direction this entity is attempting to move towards.
set_speed	Sets how fast this entity can move.
speed	Returns how fast this entity can move.

Examples

local ecs = crystal.ECS:new();
local physics_system = ecs:add_system(crystal.PhysicsSystem);

local entity = ecs:spawn(crystal.Entity);
entity:add_component(crystal.Body);
entity:add_component(crystal.Movement);
entity:set_heading(0); -- in radians

for i = 1, 100 do
  ecs:update();
  physics_system:simulate_physics(0.01);
  print(entity:position()); -- Prints entity position as it's moving to the right
end