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Posted: **Wed Apr 19, 2017 11:42 pm**

So right now I'm making an astroid-y game, however I've ran into an issue and it's driving me crazy. The ship rotates around and the value of the rotation is stored in the variable angle. Now the bullets shot out of the ship also need to come out at the same angle, and I got that to work. However, the bullets continue to use the changing angle variable. So the bullets are changing angle when the ship turns. How can I make it so the bullet maintains it's own angle when it's created. I found local variables in the lua by googling around. I tried making a local variable which stores the current value of the angle in both the update and draw functions but that didn't work. Is there anything I'm missing?

Code: Select all

debug = true
angle = math.pi
currentAngle = 0

-- player starting location and image
player = {x = love.graphics.getWidth()/2, y = love.graphics.getHeight()/2, img = nil}
-- table that holds bullet objects
bullets = {}

function love.load(arg)
  --loading images for the game
  player.img = love.graphics.newImage('assests/player.png')
  bulletImg = love.graphics.newImage('assests/bullet.png')
  backgroundImg = love.graphics.newImage('assests/starBackground.png')
end

function love.update(dt)
  if love.keyboard.isDown('escape') then
    love.event.push('quit')
  end

  if love.keyboard.isDown('a') then
    angle = angle - (dt * 5 * math.pi/2)
  end
  if love.keyboard.isDown('d') then
    angle = angle + (dt * 5 * math.pi/2)
  end
  if love.keyboard.isDown('w') then
    player.x = player.x + 200 * (math.cos(angle) * dt)
    player.y = player.y + 200 * (math.sin(angle) * dt)
  end

  if love.keyboard.isDown('space') then
    bulletExitX = player.x
    currentBullet = bulletExitX
    bulletExitY = player.y
    newBullet = {img = bulletImg, x = player.x, y = player.y, speed = 250}
    table.insert(bullets, newBullet)
  end
      for i, bullet in ipairs(bullets) do

      local angle1 = angle
      bullet.x = bullet.x + ( math.cos(angle1) * 250 * dt)
      bullet.y = bullet.y + ( math.sin(angle1) * 250 * dt)

  end

function love.draw(dt)
-- background for the screen
  love.graphics.draw(backgroundImg, love.graphics.getHeight(), love.graphics.getWidth() )
  -- draw the player image with it's origin at the center of the image
  love.graphics.draw(player.img, player.x, player.y, angle + (math.pi/2), 1, 1,  player.img:getWidth()/2, player.img:getHeight()/2)
  -- for each bullet in bullets draw them
  for i, bullet in ipairs(bullets) do
    local angle1 = angle
    love.graphics.draw(bullet.img, bullet.x, bullet.y, angle1 + (math.pi/2))
  end
end
end

Posted: **Thu Apr 20, 2017 4:15 am**

Scoots wrote: ↑Wed Apr 19, 2017 11:42 pm So right now I'm making an astroid-y game, however I've ran into an issue and it's driving me crazy. The ship rotates around and the value of the rotation is stored in the variable angle. Now the bullets shot out of the ship also need to come out at the same angle, and I got that to work. However, the bullets continue to use the changing angle variable. So the bullets are changing angle when the ship turns. How can I make it so the bullet maintains it's own angle when it's created. I found local variables in the lua by googling around. I tried making a local variable which stores the current value of the angle in both the update and draw functions but that didn't work. Is there anything I'm missing?

Hi and welcome to the forums!

When you create the bullets (and player), you can't store their own angles as a variable inside their tables as well, because...?

Code: Select all

debug = true

-- player starting location and image
player = {
    x = love.graphics.getWidth()/2,
    y = love.graphics.getHeight()/2,
    img = nil,
    angle = math.pi -- Store this in player table instead, no globals to mess with you.
}
-- table that holds bullet objects
bullets = {}

function love.load(arg)
    --loading images for the game
    player.img = love.graphics.newImage('assests/player.png')
    bulletImg = love.graphics.newImage('assests/bullet.png')
    backgroundImg = love.graphics.newImage('assests/starBackground.png')
end

function love.update(dt)
    if love.keyboard.isDown('escape') then
        love.event.push('quit')
    end

    if love.keyboard.isDown('a') then
        player.angle = player.angle - (dt * 5 * math.pi/2)
    end

    if love.keyboard.isDown('d') then
        player.angle = player.angle + (dt * 5 * math.pi/2)
    end

    if love.keyboard.isDown('w') then
        player.x = player.x + 200 * (math.cos(player.angle) * dt)
        player.y = player.y + 200 * (math.sin(player.angle) * dt)
    end

    if love.keyboard.isDown('space') then
        bulletExitX = player.x
        currentBullet = bulletExitX
        bulletExitY = player.y
        newBullet = {
            img = bulletImg,
            x = player.x,
            y = player.y,
            speed = 250,
            angle = player.angle -- Unique variable for each bullet, because you need it.
        }
        table.insert(bullets, newBullet)
    end

    for i, bullet in ipairs(bullets) do
        bullet.x = bullet.x + ( math.cos(bullet.angle) * 250 * dt)
        bullet.y = bullet.y + ( math.sin(bullet.angle) * 250 * dt)
    end
end

function love.draw(dt)
    -- background for the screen
    love.graphics.draw(backgroundImg, love.graphics.getHeight(), love.graphics.getWidth() )
    -- draw the player image with it's origin at the center of the image
    love.graphics.draw(player.img, player.x, player.y, player.angle + (math.pi/2), 1, 1,  player.img:getWidth()/2, player.img:getHeight()/2)
    -- for each bullet in bullets draw them
    for i, bullet in ipairs(bullets) do
        love.graphics.draw(bullet.img, bullet.x, bullet.y, bullet.angle + (math.pi/2))
    end
end

Posted: **Thu Apr 20, 2017 9:01 pm**

Thank you so much! I'll try to avoid global values in the future, this was causing me so much grief.

LÖVE

Value from one variable to another

Value from one variable to another

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Re: Value from one variable to another