Simple Circle Class

Cesar

I just want to share a simple Circle class

Circle = Core.class(Shape)   function Circle:init(x, y, radius) local sides=math.floor(radius/2) local angleStep=360/sides --self:setFillStyle(Shape.SOLID, 0xff0000, 1) self:setLineStyle(1, 0xff0000, 0.8) self:beginPath() self:moveTo(radius, 0)   for i = 1,sides do local angle = math.rad(i*angleStep) xx = math.cos(angle)*radius yy = math.sin(angle)*radius self:lineTo(xx,yy) end   self:endPath() self:setPosition(x,y) end

antix

@Cesar, thanks for sharing

Here's a function to test if a given x,y position is inside a circle..

function Circle:pointInCircle(x, y) local r = self.radius ^ 2 if (y - self.y) ^ 2 / r + (x - self.x) ^ 2 / r <= 1 then return true end return false end

Also, if you ever want to expand the abilities of your circle class to include collision with other circles you should checkout the following page.. http://blogs.love2d.org/content/circle-collisions, it's pretty cool stuff.

Cesar

@antix I think you can use hitTestPoint() as Circle class inherits from Sprite class. Thank you anyway.

keszegh

@Cesar, hitTestPoint() only tests against the bounding box of the sprite, so it won't work properly for a circle.

talis

As you can see in this threat also, whenever your buttons will be round not rectangular you can have some miss clicks with normal hitTestPoint() . (As button class is inheriting sprite)
http://giderosmobile.com/forum/discussion/3595/non-rectangle-button/p1

Cesar

Thank you very much for the observation

antix

@Cesar, Also if you are going to make many circles you could optimize things a little..

for i = 1,sides do local rad, sin, cos = math.rad, math.sin, math.cos local angle = rad(i*angleStep) local xx = cos(angle)*radius local yy = sin(angle)*radius self:lineTo(xx,yy) end

Making things local makes a difference

chuz0

For round buttons I use the Vector2 class; I just check the e.x,e.y:distanceTo(center_of_button), if it's shorter than the radius it's a hit.

SinisterSoft

@antix, will not making the functions local to the function rather than local to the loop be faster - I've not checked what bytecode will be produced.

antix

@chuz0, care to share your solution?

@SinisterSoft, you are most likely right. Hmm, I have MANY things to change in my codebase

SinisterSoft

I'm not sure if making things local to the app is the same speed as local to the function. It may be.

chuz0

@antix, sure, take a look here : http://giderosmobile.com/tools/vector2
I've used the method in the past, and probably it's not the most effective solution but it worked

Something like this :

game = Core.class(Sprite) function game:init()   button = Bitmap.new(Texture.new("roundbutton.png",true)) button:setAnchorPoint(.5,.5) button:setPosition(100,100)     self:addEventListener(Event.MOUSE_UP, self.onMouseUp, self)   end   function game:onMouseUp(event) local v = Vector2.new(e.x,e.y) if v:distanceTo(button:getX(),button:getY())<=button:getWidth()/2 then print("button touched") end   end

I haven't tried but it should work.

antix

@chuz0 cheers, I had not previously seen the vector2 library . I still will stick with mine since it doesn't need to do a math.sqrt