## Physics - Reducing friction upon contact

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cakexploder
Prole
Posts: 1
Joined: Sun Aug 22, 2010 3:51 am

### Physics - Reducing friction upon contact

Hey everyone. Total Lua/Löve newbie here. I'm working on a physics-based 2D sidescroller (I know, I know) and I'm having some trouble with jumping. I managed to get applyForce under control to prevent the character from flying off in to space, but upon landing friction brings the character to a stop, regardless of any x/y velocity. I'm assuming I'm missing/doing something obvious/wrong, so any input would be incredibly helpful. I've added all the source code below, feel free to pick apart anything I'm doing wrong at all - I'm here to learn!

Code: Select all

function love.load()
love.graphics.setMode(900, 400, false, true, 0)
world = love.physics.newWorld(900, 400)
world:setGravity(0, 700)
world:setMeter(64)

bodies = {}
shapes = {}

bodies[0] = love.physics.newBody(world, 900/2, 400, 0, 0)
shapes[0] = love.physics.newRectangleShape(bodies[0], 0, 0, 900, 50, 0) -- This is the ground

bodies[1] = love.physics.newBody(world, 100, 400/2, 10, 0)
shapes[1] = love.physics.newCircleShape(bodies[1], 0, 0, 20) -- Invisible shape that the sprite follows

love.graphics.setBackgroundColor(104, 136, 248)
char = love.graphics.newImage("sprite-r.gif");
char_x = 100
char_y = 100
jumplimit = false -- Default the jump limit (has the sprite jumped to max height allowed) to "no"
end

function love.update(dt)
world:update(dt) --this puts the world into motion

vel_x, vel_y = bodies[1]:getLinearVelocity( )

if love.keyboard.isDown("right") then
bodies[1]:applyForce(300, 0)
if vel_x > 200 then
bodies[1]:setLinearVelocity(200, vel_y) -- Max speed
end
char = love.graphics.newImage("sprite-r.gif"); -- Turn the sprite around
elseif love.keyboard.isDown("left") then
bodies[1]:applyForce(-300, 0)
if vel_x < -200 then
bodies[1]:setLinearVelocity(-200, vel_y)
end
char = love.graphics.newImage("sprite-l.gif"); -- Turn the sprite around
end
if love.keyboard.isDown("up") then
if jumplimit == false then -- If it's okay to jump...
if vel_y < -600 then
jumplimit = true -- You've jumped enough! (This is a little broken, allows for multiple jumps pre -600. working on it!)
else
bodies[1]:applyForce(0, -800) -- Do some jumping!
end
end
if vel_y == 0 then
jumplimit = false -- Occurs upon landing, okay to jump again!
end
end
box_x, box_y = bodies[1]:getPosition( ) -- Get the shape position so the sprite can follow
end

function love.draw()
love.graphics.draw(char, box_x, box_y-70) -- Sprite always follows the physics circle
local x1, y1, x2, y2, x3, y3, x4, y4 = shapes[0]:getBoundingBox()
local boxwidth = x3 - x2 --calculate the width of the box
local boxheight = y2 - y1 --calculate the height of the box
love.graphics.circle("fill", bodies[1]:getX(), bodies[1]:getY(), 0, 0) -- invisible
end


The Burrito
Party member
Posts: 153
Joined: Mon Sep 21, 2009 12:14 am
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### Re: Physics - Reducing friction upon contact

Reducing the friction probably isn't the best way to do it, but you can try shapes[1]:setFriction( .1 ) somewhere after you've defined shapes[1].