How to run "Actions " in Defold (SOLVED)

Questions
1

Okay so i’m a person who used to use Spritekit, and I used to use Cocos(But too much Resources… That’s why I moved to Defold) So I started using Defold because it is lightweight, easy to collaborate, and most importantly Cross-Platform… but here’s when I have a question, In both engines there’s actions that Sprites or objects can run to move or whatever… For example you could have a Sprite move to X coordinate 150; and it would, but importantly the engine would move it smoothly almost like an animation, Is there anyway to run “Actions” in Defold, for now I’m using go.set_position() to change the position of the character but is there anyway to smoothly have the character “move(Not just teleport instantly, but to almost walk there)” to a certain position ?

This is basically what I want to do

Screen Shot 2016-05-01 at 8.07.50 PM.png2560×1342 106 KB

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2

You could do this with a simple script on the sprite’s object - I haven’t done that much with SpriteKit, so this might not quite parallel how things work in that but hopefully it’s close:

function init(self)
  self.move_time = 0
  self.velocity = vmath.vector3(0)
end

function update(self, dt)
  local t0 = self.move_time
  self.move_time = self.move_time - dt
  if self.move_time < 0 then self.move_time = 0 end
  local t1 = self.move_time
  go.set_position(go.get_position() + self.velocity * (t0 - t1))
end

function on_message(self, message_id, message, sender)
  if message_id == hash("move") then
    self.move_time = message.time
    self.velocity = message.displacement / message.time
  end
end

If you attach this script to the object with the sprite, sending a message to your object like this should make it move (displacement) in (time) seconds:

msg.post("/my_object", "move", {time = (time), displacement = (displacement)})

Let me know if there’s anything I need to clarify, I’m trying to figure out how word my answer less awkwardly and it’s not working :slight_smile:

1 Like
3

So looks like it did not work… but I found an example that worked, I am just having a hard time understanding the logic of it… so this is the script I copied, an object sends a message after a trigger, and the camera Starts moving…

   go.property("speed", 70)
   Is_Started_Yet = false
  currentPositionX = 100.67755126953
    function init(self)
-- Add initialization code here
-- Remove this function if not needed
	msg.post("#camera", "acquire_camera_focus")
		
     end

    function update(self, dt)
 if Is_Started_Yet then
  local pos = go.get_world_position()
	pos.x = math.max(35, pos.x + self.speed * dt)
  go.set_position(pos)
 end
end

function on_message(self, message_id, message, sender)
-- Add message-handling code here
    -- Remove this function if not needed
   if message_id == hash("Started") then

 Is_Started_Yet = true

    end
end

'
So can you or another member here help me understand the logic of this script?

1 Like
4

go.property("speed", 70)
In stead of defining self.speed = 70 it’s defined as a property of det Gameobject. This can be set from the editor, when you click on the game object in your collection.

Is_Started_Yet = false
This is just a variable, tracking the movement-state of object. Could have been self.moving = false as well. Prevents the camera from moving before it’s supposed to.

currentPositionX = 100.67755126953
Another variable containing the objects current position. Could have been self.currentPosition = XXX. (Doesn’t look like it’s used for anything in your snippet)

function init(self)
        -- Add initialization code here
        -- Remove this function if not needed
	msg.post("#camera", "acquire_camera_focus")
 end

This just “activates” the camera upon initialization.

function update(self, dt)
    -- Only move if told by message
    if Is_Started_Yet then
       -- Get game object world position
       local pos = go.get_world_position()
       -- Set pos.x to the maximum value between 35 and current position + (70 * dt)
       pos.x = math.max(35, pos.x + self.speed * dt)
       -- Move game object to new position.
       go.set_position(pos)
   end
end

Added comments

function on_message(self, message_id, message, sender)
     -- Object got a message to start
     if message_id == hash("Started") then
        -- Toggle movement state
        Is_Started_Yet = true
    end
end

This is just the message receiver. Something is telling the camera to start moving.

2 Likes
5

If you just want to animate a game object, check out go.animate()! See http://www.defold.com/ref/go/#go.animate

3 Likes
6

So, I guess that there’s two main ways to move something:

  1. Move from point A to point B in a straight line and in a specific amount of time
  2. Move in varying direction with or without variable speed, based on either user input or some logic (AI or otherwise)

In case #1 the obvious and most performant choice would be to use go.animate() and animate position, specify a destination position, a duration and an easing function:

-- cancel any already existing animation
go.cancel_animations("my_go", "position")
-- move 100 to the right in 1.5 seconds with 0 seconds delay
go.animate("my_go", "position", go.PLAYBACK_ONCE_FORWARD, go.get_position() + vmath.vector3(100, 0, 0), go.EASING_LINEAR, 1.5, 0)

I use this kind of animation to move the aliens in the Space Invaders game I made.

In case #2 you most likely need to animate the game object programmatically based on some algorithm and according to some rules. In such a case you read user input or set some variables (speed, direction etc) and use the update(self, dt) function to continuously move the game object. Use delta-time to get consistent movement!

I created an example that shows the two ways of movement here: https://github.com/britzl/publicexamples/tree/master/examples/game_object_movement

4 Likes
7

Thank you all so much, makes so much more sense now!

1 Like