Arrow

gistfile1.txt

--Physics 6a
--Arrow

displayMode(FULLSCREEN)

function setup()
    arrows={}
end

function AddArrow()
    table.insert(arrows,Ballistics(vec2(50,10+math.random(30,100)),
                    vec2(.95+.1*math.random(),.95+.1*math.random()),
                    math.random(225,275),
                    .01,color(255,255,0),2,30))
end

function draw()
    background(0)
    AddArrow()
    for i,p in pairs(arrows) do 
        p:draw()
        if p.position.x>WIDTH or p.position.y<0 then table.remove(arrows,i) end
    end
end

-- Physics Library class below ---
Ballistics = class()

--constants which apply to all physics objects
Ballistics.gravityStrength=vec2(0,-133) --not accurate

--parameters are position,velocity,speed,mass,color,diameter,length
function Ballistics:init(position,direction,speed,mass,colour,diameter,length)
    --these properties belong to our physics object
    self.position=position
    self.velocity=direction*speed
    self.mass=mass
    self.color=colour or color(0)
    self.width,self.length=diameter,length
    --initialise
    self.damping= 0.99
    self.acceleration = vec2(0,0) --w.accel   
    Ballistics.gravityOn=true 
end

function Ballistics:draw()
    self:AdjustPosition(DeltaTime) 
    pushMatrix()
        fill(self.color)
        pushMatrix()
        local a=math.deg(math.atan(self.velocity.x/self.velocity.y))
        translate(self.position.x, self.position.y)
        rotate(-a)
        ellipse( 0,0, self.width ,self.length)
        popMatrix()
    popMatrix()
end

function Ballistics:AdjustPosition(t)
    --update speed
    if Ballistics.gravityOn then 
        self.acceleration = self.acceleration + Ballistics.gravityStrength 
    end
    self.velocity = self.velocity + self.acceleration * t
    --set (x,y) position
    self.position = self.position + self.velocity * t
    --reset acceleration to 0
    self.acceleration=vec2(0,0)
end