Jump not working

Questions
1

There is an issue with my jump for my character, when jump is pressed the y value increases but i dont know how to get the player back to the ground.

local jump_speed = 400
-- Initalise the script
function init(self)
	msg.post(".", "acquire_input_focus") 
	self.vel = vmath.vector3()
	self.anim = nil 	
end

-- movement
function update(self, dt)
	local pos = go.get_position() 
	pos = pos + self.vel * dt 
	go.set_position(pos) 

	self.vel.x = 0 
	self.vel.y = 0

end

--keyboard input
function on_input(self, action_id, action)
	if action_id == hash("left") then
		play_animation(self, (hash "walk_hero"))
		sprite.set_hflip("#sprite", true)
		self.vel.x = -200 
	elseif action_id == hash("right") then
		play_animation(self, (hash "walk_hero"))
		sprite.set_hflip("#sprite", false)
		self.vel.x = 200
	elseif action_id == hash("up") then 
		play_animation(self, (hash "jump_hero"))
		self.vel.y = jump_speed
	end
end

thanks

2 
	if self.vel.y > 0 then
		self.vel.y = jump_speed * 0.8

i tried with some code but its not working

3

You’re not applying any gravity to the character. There are a number of examples and tutorials showing this:

1 Like
4

i looked at a tutorial and i tried to apply some code however now my character just floats up really slowly , idk what to do

-- It flips the character sprite
local function play_animation(self, animation)
	if self.current_animation ~= animation then
		self.current_animation = animation
		sprite.play_flipbook("#sprite", animation)
	end
end

local gravity = 500
local jump_speed = 400
-- Initalise the script
function init(self)
	msg.post(".", "acquire_input_focus") 
	self.vel = vmath.vector3()
	self.anim = nil 	
end

-- movement
function update(self, dt)
	self.vel.y = self.vel.y + gravity * dt
	local pos = go.get_position() 
	pos = pos + self.vel * dt 
	go.set_position(pos) 

	
	self.vel.x = 0 
	self.vel.y = 0

end

local function jump(self) 
	self.vel.y = jump_speed
	play_animation(self, (hash "jump_hero"))
end

local function stop(self)
	if self.vel.y > 0 then
		self.vel.y = self.vel.y * 0.5
	end
end

--keyboard input
function on_input(self, action_id, action)
	if action_id == hash("left") then
		play_animation(self, (hash "walk_hero"))
		sprite.set_hflip("#sprite", true)
		self.vel.x = -200 
	elseif action_id == hash("right") then
		play_animation(self, (hash "walk_hero"))
		sprite.set_hflip("#sprite", false)
		self.vel.x = 200
	elseif action_id == hash("up") then 
		if action.pressed then
			jump(self)
		elseif action.released then
			stop(self)
		end
	end
end
5

Note that the Defold coordinate system has origin in the lower left corner of the screen and that moving up on the y-axis increases the y position. What you are doing now is applying a gravity that moves the character up, not down. Set gravity to -500 and try again.

1 Like
6

I also notice your value for gravity is way too high. Bear in mind that it is applied every frame so you’ll need something like -25 for the gravity, otherwise the player is going to be slammed into the ground the whole time.

7

Note that the gravity is multiplied by dt!

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8

i changed my gravity but now the character just sinks through the floor and his jump isnt that high

9

Yes, if you’re using kinetic collision shapes you need to handle collision yourself. E.g. handle the case when the player lands on a platform.

10

There are many tuturials on how to design jump mechnisms online,
here’s one

2 Likes
11

Have you compared your project to any of the resources I shared?

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12

how do i do that

13

It’s shown in the tutorials and examples I shared. Have you looked at any of those yet?

1 Like
14

i got it working using Resolving kinematic collsions in Defold thanks for your help

2 Likes