So I’m pretty new to defold, and am trying to learn basic best practices for capturing player input.
In one of the very basic tutorials, player input is handled in the “on_input” function, by basically setting a variable to say that a key has been pressed (in this case, if the up arrow has been pressed, we set the variable “self.input.y” to 1.) Then, the movement is actually implemented in the “update” function, by checking to see if self.input.y is equal to 1, and if so, we move the player character up, and finally, we set self.input.y to 0 at the end of the function, so that if the up arrow is not pressed during the next game loop, we will not continue moving up.
This approach works well, and seem logical to me, as executing movement inside the “update” function instead of during the “on_input” function allows us to do things like check if multiple keys are pressed at the same time, and change behavior accordingly, etc.
However, I have run into a problem while trying to implement this same approach while using a fixed time step. As far as I can tell, the “on_input” function is triggered during every game loop when using a variable timestep, but when using a fixed timestep, every 50 frames or so (on my pc, anyways) there will randomly be a loop where the “fixed_update” function runs, but the “on_input” function does not, even while holding a key down continuously.
I’m including the full test script at the end of this post; if you build a game with an object running that script, and hold down the up arrow key, it constantly prints “input” in the console, reliably doing so every frame until you release the arrow key. However, if you change the “update” function to “fixed_update” and enable “Use Fixed Timestep” in the game settings, then build the game and test out holding the up arrow continuously, it will have a (seemingly random) loop every second or so where it prints “no input”, meaning it thought the key wasn’t pressed.
So my question is: how should input be handled when using a fixed timestep? If I do like the tutorial indicates and set a variable during the “on_input” function, and then use that variable during the “fixed_update” function to determine if the key is pressed, there will be random frames where it thinks the key isn’t pressed, and motion will be jittery.
Any advice and/or guidance would be greatly appreciated. Thanks!
function init(self) -- [1]
msg.post(".", "acquire_input_focus") -- [2]
self.moving = false -- [3]
self.input = vmath.vector3() -- [4]
self.dir = vmath.vector3(0, 1, 0) -- [5]
self.speed = 50 -- [6]
end
function final(self) -- [7]
msg.post(".", "release_input_focus") -- [8]
end
function update(self, dt) -- [9]
if self.moving then
print('input')
else
print('no input')
end
self.input.x = 0 -- [13]
self.input.y = 0
self.moving = false
end
function on_input(self, action_id, action) -- [14]
if action_id == hash("up") then
self.input.y = 1 -- [15]
elseif action_id == hash("down") then
self.input.y = -1
elseif action_id == hash("left") then
self.input.x = -1
elseif action_id == hash("right") then
self.input.x = 1
end
if vmath.length(self.input) > 0 then
self.moving = true -- [16]
self.dir = vmath.normalize(self.input) -- [17]
end
end
