How handle with angle?

General
1

Hi, kind folks, i have some problem with rotating object on the screen. I will try explain my problem clearly.
I have one rectangle on the screen (more precisely png image) and i need rotate it accordingly player touches. I used angleBetween() func, but it not so accurately (or i misunderstand this func). There is my class and screenshots:

Lasers = class()

function Lasers:init()
    -- you can accept and set parameters here
    self.laserx = WIDTH/2+20
    self.lasery = 130
    self.angle = 0
    self.vec = vec2(WIDTH/2,0)
end

function Lasers:draw()
    -- Codea does not automatically call this method
    self.angle = math.deg(self.vec:angleBetween(vec2(CurrentTouch.x,CurrentTouch.y)))
    pushMatrix()
    translate(self.laserx,self.lasery)
    
    if CurrentTouch.x < WIDTH/2 then
        rotate(-self.angle)
        else 
        rotate(self.angle)
    end
    print(self.angle)
    sprite("Documents:Laser",0,0,1024/6,768/6)
    popMatrix()
end


2

@lupino8211 Try this.


displayMode(FULLSCREEN)

function setup()
    rectMode(CORNER)
    angle=0 -- angle
    lx=300  -- laser x
    ly=100  -- laser y
end

function draw()
    background(0)
    
    fill(255)
    sprite("Platformer Art:Hill Tall",300,100)
    
    pushMatrix()
    translate(lx,ly)
    rotate(angle)
    rect(0,0,100,10) 
    popMatrix()   
end


function touched(t)
    if t.state==BEGAN then
        angle=math.deg(math.atan2(t.y-ly,t.x-lx))
    end
end
3

@dave1707 thank you very much!

4

If you look carefully at the screen, the direction that the laser is pointing in is parallel to the line joining the lower-left of the screen to the point where you touch. That’s because the self.vec:angleBetween(CurrentTouch.x,CurrentTouch.y) computes the angle subtended at the origin which is the lower-left of the screen. What Dave’s code does is relocate that to the pivot of the laser arm.

5

Here’s the code above, but using angleBetween instead of atan2. I’m not sure if one has an advantage over the other. I also added code for a bullet.


displayMode(FULLSCREEN)

function setup()
    angle=0 -- angle
    lx=300  -- laser x
    ly=100  -- laser y
    ex=-5
    ey=-5
    dir=vec2(0,0)
end

function draw()
    background(0)        
    sprite("Platformer Art:Hill Tall",300,100)
    
    pushMatrix()
    translate(lx,ly)
    rotate(angle)
    rect(0,-5,100,10) 
    popMatrix() 
    
    ex=ex+dir.x*10
    ey=ey+dir.y*10
    fill(255)
    ellipse(ex,ey,8)
end


function touched(t)
    if t.state==BEGAN then
        angle=math.deg(vec2(0,0):angleBetween(vec2(t.x-lx,t.y-ly)))
        v1=vec2(t.x-lx,t.y-ly)
        dir=v1:normalize()
        ex=lx
        ey=ly
    end
end
6

@LoopSpace thank you for explanation , and @Dave1707 thank you for another example