move object up down with math.sin

Solar2D General Questions/Discussion
#1

hi

can somebody convert the code below to corona code

it should basically move an object up and down using math.sin

var numberOfTicks = 0;

function gameLoop() {

    numberOfTicks++;

    ufo.y = (250 * sin(numberOfTicks * 0.5 * pi)) + 350;

    ufo.x += ufo.xSpeed;

}

thanks

this page is from

http://gamedevelopment.tutsplus.com/tutorials/quick-tip-create-smooth-enemy-movement-with-sinusoidal-motion–gamedev-6009

#2

It’s pretty easy and you should definitly try to understand it yourself, as JavaScript and LUA are quite similar.

local numberOfTics = 0 local ySpeed = 0.5 local function gameLoop() ufo.y = (250\*math.sin(numberOfTicks\*ySpeed\*math.pi)) + 350 ufo.x = ufo.x + ufo.xSpeed numberOfTics = numberOfTics + 1 end

I added a ySpeed value, which you can alter to your needs.

#3

HI

could not manage to get anything moving i am using code as below

can somebody try the code with moving an object

local ufo = display.newRect( 500, 500, 15, 15 )

local numberOfTics = 0
local ySpeed = 0.5

local function gameLoop()
ufo.y = (250*math.sin(numberOfTicks*ySpeed*math.pi)) + 350
ufo.x = ufo.x + ufo.xSpeed
numberOfTics = numberOfTics + 1
end

thankyou

#4

Well, of course you need an enterFrame listener to call the gameLoop.

Runtime:addEventListner("enterFrame", gameLoop)

Call this after you declared the gameLoop function.

#5

HI

ok im trying this code , but seems object just moves right along the screen and not up and down

local ufo = display.newRect( 500, 500, 15, 15 )

local numberOfTics = 0
local ySpeed = 2.5

local function gameLoop( event )
   ufo.y = (250*math.sin(numberOfTicks*ySpeed*math.pi)) + 350
   ufo.x = ufo.x + 20 --ufo.xSpeed
   numberOfTics = numberOfTics + 1
end

Runtime:addEventListener(“enterFrame”, gameLoop)
 

your help much appreciated

#6

You need a much lower value for ySpeed.

One sinus wave goes from zero (0) to two pi (6.2831…), so if you multiply pi with a values greater than 1 there wont be much going on.

Take something in the range 0.01 to 0.1 or even smaller.

#7

Still no joy, still seems to move horizontal only

can somebody actually try the code

local ufo = display.newRect( 500, 500, 15, 15 )

local numberOfTics = 0
local ySpeed = 0.1

local function gameLoop( event )
   ufo.y = (250*math.sin(numberOfTicks*ySpeed*math.pi)) + 350
   ufo.x = ufo.x + 20 --ufo.xSpeed
   numberOfTics = numberOfTics + 0.1
end

Runtime:addEventListener(“enterFrame”, gameLoop)
 

#8

I tried the code above and it does move downward on the screen. I modified it to slow the x axis speed of the object, so that you can see the behavior yourself:

local ufo = display.newRect( display.contentCenterX, display.actualContentHeight, 15, 15 ) local numberOfTics = 0 local ySpeed = 0.1 local function gameLoop( event ) ufo.y = (250\*math.sin(numberOfTics\*ySpeed\*math.pi)) ufo.x = ufo.x + 2 --ufo.xSpeed numberOfTics = numberOfTics + 0.1 end Runtime:addEventListener("enterFrame", gameLoop)
#9

It’s pretty easy and you should definitly try to understand it yourself, as JavaScript and LUA are quite similar.

local numberOfTics = 0 local ySpeed = 0.5 local function gameLoop() ufo.y = (250\*math.sin(numberOfTicks\*ySpeed\*math.pi)) + 350 ufo.x = ufo.x + ufo.xSpeed numberOfTics = numberOfTics + 1 end

I added a ySpeed value, which you can alter to your needs.

#10

HI

could not manage to get anything moving i am using code as below

can somebody try the code with moving an object

local ufo = display.newRect( 500, 500, 15, 15 )

local numberOfTics = 0
local ySpeed = 0.5

local function gameLoop()
ufo.y = (250*math.sin(numberOfTicks*ySpeed*math.pi)) + 350
ufo.x = ufo.x + ufo.xSpeed
numberOfTics = numberOfTics + 1
end

thankyou

#11

Well, of course you need an enterFrame listener to call the gameLoop.

Runtime:addEventListner("enterFrame", gameLoop)

Call this after you declared the gameLoop function.

#12

HI

ok im trying this code , but seems object just moves right along the screen and not up and down

local ufo = display.newRect( 500, 500, 15, 15 )

local numberOfTics = 0
local ySpeed = 2.5

local function gameLoop( event )
   ufo.y = (250*math.sin(numberOfTicks*ySpeed*math.pi)) + 350
   ufo.x = ufo.x + 20 --ufo.xSpeed
   numberOfTics = numberOfTics + 1
end

Runtime:addEventListener(“enterFrame”, gameLoop)
 

your help much appreciated

#13

You need a much lower value for ySpeed.

One sinus wave goes from zero (0) to two pi (6.2831…), so if you multiply pi with a values greater than 1 there wont be much going on.

Take something in the range 0.01 to 0.1 or even smaller.

#14

Still no joy, still seems to move horizontal only

can somebody actually try the code

local ufo = display.newRect( 500, 500, 15, 15 )

local numberOfTics = 0
local ySpeed = 0.1

local function gameLoop( event )
   ufo.y = (250*math.sin(numberOfTicks*ySpeed*math.pi)) + 350
   ufo.x = ufo.x + 20 --ufo.xSpeed
   numberOfTics = numberOfTics + 0.1
end

Runtime:addEventListener(“enterFrame”, gameLoop)
 

#15

I tried the code above and it does move downward on the screen. I modified it to slow the x axis speed of the object, so that you can see the behavior yourself:

local ufo = display.newRect( display.contentCenterX, display.actualContentHeight, 15, 15 ) local numberOfTics = 0 local ySpeed = 0.1 local function gameLoop( event ) ufo.y = (250\*math.sin(numberOfTics\*ySpeed\*math.pi)) ufo.x = ufo.x + 2 --ufo.xSpeed numberOfTics = numberOfTics + 0.1 end Runtime:addEventListener("enterFrame", gameLoop)