[SOLVETH] Physics - can't set mass of a body.

[Beliar]

Hello there.

I've been playing with the physics tutorial code, and I couldn't find a way to change the mass of a body. I've tried everything but the thing always stays the same, like if the masses are more or less equal. If i have a 5000kg ball and a 1kg brick, the brick won't stop the ball easily, i'm trying to reproduce something like this.

Here is the code:

Code: Select all

function love.load()
  love.physics.setMeter(64) --the height of a meter our worlds will be 64px
  world = love.physics.newWorld(0, 9.81*64, false) --create a world for the bodies to exist in with horizontal gravity of 0 and vertical gravity of 9.81

  objects = {} -- table to hold all our physical objects
 
  --let's create the ground
  objects.ground = {}
  objects.ground.body = love.physics.newBody(world, 650/2, 650-50/2) --remember, the shape (the rectangle we create next) anchors to the body from its center, so we have to move it to (650/2, 650-50/2)
  objects.ground.shape = love.physics.newRectangleShape(650, 50) --make a rectangle with a width of 650 and a height of 50
  objects.ground.fixture = love.physics.newFixture(objects.ground.body, objects.ground.shape); --attach shape to body
 
	objects.ground1 = {}
  objects.ground1.body = love.physics.newBody(world, 2, 2) --remember, the shape (the rectangle we create next) anchors to the body from its center, so we have to move it to (650/2, 650-50/2)
  objects.ground1.shape = love.physics.newRectangleShape(50, 6500) --make a rectangle with a width of 650 and a height of 50
  objects.ground1.fixture = love.physics.newFixture(objects.ground1.body, objects.ground1.shape); --attach shape to body
 
	objects.ground1 = {}
  objects.ground1.body = love.physics.newBody(world, 648, 2) --remember, the shape (the rectangle we create next) anchors to the body from its center, so we have to move it to (650/2, 650-50/2)
  objects.ground1.shape = love.physics.newRectangleShape(50, 6500) --make a rectangle with a width of 650 and a height of 50
  objects.ground1.fixture = love.physics.newFixture(objects.ground1.body, objects.ground1.shape); --attach shape to body

 
  --let's create a ball
  objects.ball = {}
  objects.ball.body = love.physics.newBody(world, 650/2, 650/2, "dynamic") --place the body in the center of the world and make it dynamic, so it can move around
  objects.ball.body:setMassData(1,1,1000,0) --give it a mass of 15
  objects.ball.shape = love.physics.newCircleShape(20) --the ball's shape has a radius of 20
  objects.ball.fixture = love.physics.newFixture(objects.ball.body, objects.ball.shape, 1) --attach shape to body and give it a friction of 1
  objects.ball.fixture:setRestitution(0.0) --let the ball bounce

  --let's create a couple blocks to play around with
  objects.block1 = {}
  objects.block1.body = love.physics.newBody(world, 200, 550, "dynamic")
  objects.block1.body:setMassData(1,1,1,0) --uff, very heavy block at the bottom
  objects.block1.shape = love.physics.newRectangleShape(0, 0, 50, 100)
  objects.block1.fixture = love.physics.newFixture(objects.block1.body, objects.block1.shape, 5) --with plenty of friction, will be hard to move around

  t={}
  
  for i = -29, -27, 1 do
  
  block2 = {}
  block2.body = love.physics.newBody(world, 100, i*-16.5, "dynamic")
  block2.body:setMassData(7,7,0.001,10)
  block2.shape = love.physics.newRectangleShape(0, 0, 15, 15)
  block2.fixture = love.physics.newFixture(block2.body, block2.shape, 2)
  table.insert(t,block2)

  end
  
  
  --initial graphics setup
  love.graphics.setBackgroundColor(104, 136, 248) --set the background color to a nice blue
  love.graphics.setMode(650, 650, false, true, 0) --set the window dimensions to 650 by 650
end


function love.update(dt)
  world:update(dt) --this puts the world into motion
 
  --here we are going to create some keyboard events
  if love.keyboard.isDown("right") then --press the right arrow key to push the ball to the right
    objects.ball.body:applyForce(4000, 0)
  elseif love.keyboard.isDown("left") then --press the left arrow key to push the ball to the left
    objects.ball.body:applyForce(-4000, 0)
  elseif love.keyboard.isDown("up") then --press the up arrow key to set the ball in the air
    objects.ball.body:setPosition(650/2, 650/2)
  end
end

function love.draw()
  love.graphics.setColor(72, 160, 14) -- set the drawing color to green for the ground
  love.graphics.polygon("fill", objects.ground.body:getWorldPoints(objects.ground.shape:getPoints())) -- draw a "filled in" polygon using the ground's coordinates

  love.graphics.setColor(193, 47, 14) --set the drawing color to red for the ball
  love.graphics.circle("fill", objects.ball.body:getX(), objects.ball.body:getY(), objects.ball.shape:getRadius())

  love.graphics.setColor(50, 50, 50) -- set the drawing color to grey for the blocks
  love.graphics.polygon("fill", objects.block1.body:getWorldPoints(objects.block1.shape:getPoints()))
  
  
  
  
  
  
  
  
  
  
  for index,value in ipairs(t) do 

	love.graphics.polygon("fill", value.body:getWorldPoints(value.shape:getPoints()))
  end
  
  
  
  --love.graphics.polygon("fill", objects.block2.body:getWorldPoints(objects.block2.shape:getPoints()))
  
  
  
  
  
end

Any clues?

Thank you guys.

[Beliar]

Hah! Now we're talking!

Just added objects.ball.body:resetMassData() after setting the mass and it worked like a charm.

[juno]

The 0.8.0 version messed with with masses of my objects big time...
It seems that what ever value you give for the density of the body, Love takes that value and produces a mass value in conjunction with the shape(s) volume.
You can manually alter the mass of the body by using body:setMassData() and then body:resetMassData() for it to take effect.
If you can, you should output the computed mass of each body "Body:getMass()" to the screen to see which objects are heavier...Then alter the density and see if it has much effect.

[Beliar]

OK, thanks for the clarification.