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Tutorial:Platformer Jumping
| This tutorial is incomplete. Do you want to complete it? |
Due to a request on IRC, this guide has been written to show a basic implementation of platformer-style jumping physics for a player character.
The tutorial is fairly basic and even a newbie should have no issue understanding.
First, let's start off with our basic code, without any jumping.
player = { -- nice and organised.
x = 0,
y = 0,
image = love.graphics.newImage("hamster.png") -- let's just re-use this sprite.
}
winW, winH = love.graphics.getWidth(), love.graphics.getHeight() -- this is just
-- so we can draw it in a fabulous manner.
end
function love.draw()
love.graphics.rectangle("fill", 0, winH / 2, winW, winH / 2)
love.graphics.translate(winW / 2, winH / 2) -- you don't need to understand this
love.graphics.draw(player.image, player.x, -player.y, 0, 1, 1, 64, 103) -- trust me
-- on the origin position. just trust me.
end
- Note: The hamster.png file is File:Resource-HamsterBall.png.
You should get something that looks like this:
Now, it's time to make it jump. To do this, we'll give the player an upwards velocity, create a gravity variable and a jump height variable.
Add this to your love.load function:
...
y_velocity = 0,
}
...
gravity = 400
jump_height = 300
When the player presses the jump button (spacebar for this tutorial) we will increase the x_velocity by the jump_height.
Then, we will move the player upwards while decreasing the velocity by the gravity. We'll add a love.update and love.keypressed callback to make this work.
if player.y_velocity ~= 0 then -- we're probably jumping
player.y = player.y + player.y_velocity * dt -- dt means we wont move at
-- different speeds if the game lags
player.y_velocity = player.y_velocity - gravity * dt
if player.y < 0 then -- we hit the ground again
player.y_velocity = 0
player.y = 0
end
end
end
function love.keypressed(key)
if key == " " then
if player.y_velocity == 0 then -- we're probably on the ground, let's jump
player.y_velocity = jump_height
end
end
end
Yay, jumping!
However, this is not true platformer-style jumping. In a lot of platformers, holding the jump key makes you jump higher. Let's implement this.
First, let's create a new player variable in love.load.
...
jetpack_fuel = 0.5, -- note: not an actual jetpack. variable is the time (in seconds)
-- you can hold spacebar and jump higher.
jetpack_fuel_max = 0.5,
}
Now, we remove our love.keypressed callback. We won't exact time, which is just bothersome to find out using keypressed and keyreleased. Instead, we'll move that logic to love.update.
....glhf
if player.jetpack_fuel > 0 -- we can still move upwards
and love.keyboard.isDown(" ") then -- and we're actually holding space
player.jetpack_fuel = player.jetpack_fuel - dt -- decrease the fuel meter
player.y_velocity = player.y_velocity + jump_height * (dt / player.jetpack_fuel_max)
end
if player.y_velocity ~= 0 then -- we're probably jumping
player.y = player.y + player.y_velocity * dt -- dt means we wont move at
-- different speeds if the game lags
player.y_velocity = player.y_velocity - gravity * dt
if player.y < 0 then -- we hit the ground again
player.y_velocity = 0
player.y = 0
player.jetpack_fuel = player.jetpack_fuel_max
end
end
end
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