How can I get rid of this extra math

Tom2012

In the code below I need to fire something towards another object using Atan2, cos and sin

It works, but I'm converting to degrees and then back to radians. (I'm guessing this has some overhead).

Snippet:

local angle = math.atan2(yDiff,xDiff) angle = math.deg(angle) + 180   local nextX = ball:getX() + (math.cos(math.rad(angle)) * move) local nextY = ball:getY() + (math.sin(math.rad(angle)) * move)

Is there a better way to 'reverse' the angle?

Thank you!

-- Add hero   local hero = Bitmap.new(Texture.new("gfx/happy-block.png")) hero:setAnchorPoint(.5,.5) stage:addChild(hero) hero:setPosition(100,100)   -- Add ball   local ball = Bitmap.new(Texture.new("gfx/ball.png")) ball:setAnchorPoint(.5,.5) stage:addChild(ball) ball:setPosition(400,200)     -- pixels moved each frame local move = 1;   local moving = false -- keep track of if ball already moving   -- This function moves the ball each frame   function moveBall()   local xDiff = ball:getX() - hero:getX() local yDiff = ball:getY() - hero:getY()   local angle = math.atan2(yDiff,xDiff) angle = math.deg(angle) + 180   local nextX = ball:getX() + (math.cos(math.rad(angle)) * move) local nextY = ball:getY() + (math.sin(math.rad(angle)) * move)   --print(nextX, nextY)   ball:setPosition(nextX,nextY)   end   function touchedEnd(event)   if(not moving) then   moving = true ball:setPosition(event.touch.x, event.touch.y) -- move ball to touch x,y stage:addEventListener(Event.ENTER_FRAME, moveBall) -- add event listener to move ball each frame     end   end   stage:addEventListener(Event.TOUCHES_END, touchedEnd)

techdojo

As both sin, cos and atan2 all work in radians, why not just work in radians all the time and in the line

angle = math.deg(angle) + 180

change it to

angle = angle + (180 * 0.0174532925) -- 1 degrees = 0.0174532925 radians

Tom2012

Ah, thanks. That works great.

zvardin

Also, I believe I read you can get some improvements by storing math functions into local functions when you're going to be using them a lot.

So, you can store any math functions you're going to use like:

local sin = math.sin

techdojo

@Tom2012 - absolutely, should have mentioned that

OZApps

...and set up a variable to contain the constant deg2rad so that you know what that magic number is/was when you revisit the code.