How do you create a follow camera?

Questions
1

Hi everyone, this is my first post so bear with me! I am trying to create a camera to follow my ball and I can’t figure it out… If anyone has any tips please feel free to share! I have provided the code below feel free to use and improve it. Thanks!


--# Main
-- Phisics Project
displayMode(FULLSCREEN)
supportedOrientations(LANDSCAPE_RIGHT)
-- Use this function to perform your initial setup
function setup()
    
-- parameter.boolean("UseAccelerometer")
    bullets = {}
    
    ball = physics.body(CIRCLE, 28)
    ball.x = WIDTH/1.9
    ball.y = HEIGHT/2
    ball.restitution = .9
    ball.gravityScale = 0
    ball.sensor = true
    
    floor = physics.body(EDGE, vec2(0,0), vec2(WIDTH, 0))
    floor.restitution = 0
    rightWall = physics.body(EDGE, vec2(WIDTH,0), vec2(WIDTH,HEIGHT))
    rightWall.restitution = 0
    leftWall = physics.body(EDGE, vec2(0,0), vec2(0, HEIGHT))
    leftWall.restitution = 0
    ceiling = physics.body(EDGE, vec2(0,HEIGHT), vec2(WIDTH, HEIGHT))
    ceiling.restitution = 0
    
  defaultGravity = physics.gravity()
    bgLines = StreamingLines()
    
end

-- This function gets called once every frame
function draw()
    -- This sets a dark background color
    background(0, 0, 0, 255)
    
    bgLines.spawnRate = BackgroundSpawnRate
    bgLines:update()
    bgLines:draw()
    
    
    physics.gravity(Gravity)
    
    -- This sets the line thickness
    strokeWidth(5)
    ellipse(ball.x, ball.y, 55)
    pushStyle()
    fill(251, 1, 35, 255)
    for i, bullet in ipairs(bullets) do
        ellipse(bullet.x, bullet.y, 10)
      --  bullet.y = bullet.y + 5
    end
    popStyle()
      --   if UseAccelerometer == true then
  --  physics.gravity(Gravity)
--else
    --  physics.gravity(defaultGravity)
 -- end 
    fill(0, 0, 0, 255)
    ball.x = ball.x +Gravity.x *5
    ball.y = ball.y +Gravity.y*5
    -- Do your drawing here
end

function touched(touch)
    if touch.state == BEGAN then
       
        dx = touch.x - ball.x
        dy = touch.y - ball.y
        theta = math.atan(dx,dy)
        deg = (theta * (180 / math.pi) -90)*-1
        
        --angle = math.tan(theta)
        print("degree"..deg)
        
        y = math.sin(deg)*100
        x = (math.cos(deg)*100)*-1
        print("x"..x)
        print(y)

        
        bullet = physics.body(CIRCLE, 10)
        bullet.x = ball.x 
        bullet.y = ball.y 
        bullet.gravityScale = 0
        
        
         bullet:applyForce(vec2(dx,dy))
        table.insert(bullets, bullet)
       
    end
end

--# Lines
--parameter.boolean("UseAccelerometer", true)
StreamLine = class()
function StreamLine:init(pos, vel)
    self.position = pos
    self.velocity = vel
end

function StreamLine:update()
    self.position.y = self.position.y - self.velocity
end

function StreamLine:draw()
    p = self.position
    line(p.x + Gravity.x*200,p.y,p.x + Gravity.x * 200,p.y + self.velocity)
end

function StreamLine:shouldCull()
    -- Check if off the bottom of the screen
    if (self.position.y + self.velocity) < 0 then
        return true
    end 

    return false
end


StreamingLines = class()

function StreamingLines:init()
    self.minSpeed = 5
    self.speed = 30
    self.spawnRate = 2
    self.lines = {}
end

function StreamingLines:updateAndCull()
    toCull = {}
    for i,v in ipairs(self.lines) do
        if v:shouldCull() then
            -- table.insert( toCull, i )
            table.remove( self.lines, i )
        else
            v:update()
        end
    end

    -- print("Removing ", #toCull)
    --for i = #toCull,1,-1 do
    --    table.remove( self.lines, i )
    --end
end

function StreamingLines:update()
    -- Create spawnRate lines per update
     i = 1,self.spawnRate do
        -- Generate random spawn location
        vel = math.random(self.minSpeed, self.speed)
        spawn = vec2( math.random(WIDTH), HEIGHT + vel )

        table.insert(self.lines, StreamLine(spawn, vel))
    end

    -- Update and cull offscreen lines
    self:updateAndCull()
end

function StreamingLines:draw()
    --print("Num lines = ", #self.lines)

    pushStyle()

    noSmooth()
    stroke(179, 153, 180, 173)
    strokeWidth(2)
    lineCapMode(SQUARE)
    
    for i,v in ipairs(self.lines) do
        v:draw()
    end

    popStyle()
  
      --   if UseAccelerometer == true then
       --physics.gravity(Gravity)
   --else
     --  physics.gravity(defaultGravity)
 --  end 

end
2

@Bboy When you post code, put 3 ~'s on a line before and after your code so it shows correctly. I added them to your code.

3

Good to know, thanks! If you have time, do you know how to create a camera that follows the ball?@dave1707

4

@Bboy There was another post that used the camera command to keep something centered in the screen while the background moved around. I’ve been trying to find it, but I haven’t had any luck so far. Maybe someone else will give you the info while I continue to search.

5

@Bboy - From the LuaJump demo project

-- Center the camera on the girl character
    camPos = vec2(WIDTH/2, 
                  math.min(HEIGHT/2 - girl.position.y, 140))
    translate(camPos.x,camPos.y)
6

Awesome thank you! @Ignatz

7

This is what I use:

myThing = vec3(200,300,200)
camera(myThing.x, myThing.y, myThing.z - 300, myThing.x, myThing.y, 0)
perspective()