Trigger

This example shows how a physics trigger is used to trigger an event. In this case the bunny sprite is disabled and enabled.

Project files

The setup consists of two game objects.

trigger

The invisible trigger. Contains:

A Collision object component. The Type is set to TRIGGER. A box Shape is added to the components.

bunny

The bunny. Contains:

A Sprite component with the bunny image.
A Collision object component. It has Type set to DYNAMIC. A sphere Shape matching the sprite image is added to the components.
A Script component that animates the bunny’s position and reacts to physics messages when interacting with the trigger.

Scripts

bunny.script

function init(self)
	local pos = go.get_position() -- <1>
	go.animate(".", "position.x", go.PLAYBACK_LOOP_PINGPONG, pos.x + 600, go.EASING_INOUTSINE, 6)
end

function on_message(self, message_id, message, sender)
	if message_id == hash("trigger_response") then -- <2>
		if message.enter then -- <3>
			msg.post("#sprite", "disable") -- <4>
		else
			msg.post("#sprite", "enable") -- <5>
		end
	end
end

--[[
1. Get the current position, then animate the position's x component
   looping in a ping-pong manner against an offset of 600.
2. The physics engine has detected that this game object contains
   collision object components that have collided with a trigger.
3. The `message` data table contains a field `enter` that is set
   to `true` when the trigger event signals that the trigger shape
   was entered. On exiting the trigger, this field is `false`.
4. Disable the sprite when the trigger is entered
5. Enable the sprite again on exit.
--]]