Help with getting a constant velocity with random forces

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#1

Hello. I am making a game where a dynamic object randomly moves around the screen. My current code makes sure the two forces add up to a certain value. However this does not give the same velocity. Would there be any way to do that?

Here is my code currently

local impulseVal = 400 local impulseX local impulseY local signDet1 local signDet2local mRand = math.random math.randomseed( os.time() ) local function bubbleClick() --remove later bubble:setFillColor(55,10,0 ) print("rand") --get random number impulseX = mRand(0,impulseVal) impulseY = impulseVal - impulseX signDet1 = mRand(0,1) if signDet1 == 0 then impulseX = impulseX \* 1 elseif signDet1 == 1 then impulseX = impulseX \* -1 end signDet2 = mRand(0,1) if signDet2 == 0 then impulseY = impulseY \* 1 elseif signDet1 == 1 then impulseY = impulseY \* -1 end bubble:applyForce(impulseX,impulseY,bubble.x,bubble.y) end

I cannot use transition to because that messes up my object’s x and y coordinates.

Any help is greatly appreciated!

#2

It is going to be extremely difficult to work out the object’s velocity from the applied force. I’ve been there - avoid it if you can. This is a Box2D thing and incredibly complex.

If you want to know what the velocity is, you should simply set it:

http://docs.coronalabs.com/daily/api/type/Body/setLinearVelocity.html

http://docs.coronalabs.com/daily/api/type/Body/angularVelocity.html

#3

Hey, thanks for the advice. Instead of using applyForce I used setLinerVelocity with my randomly generated numbers. However my object still has varying velocities. Do you know of a way that I could set a global velocity value and split that number into x and y components of varying values. Then randomly decide if each one is either positive or negative?

Thanks for the help!

#4

I still have had no luck. Is there any way to give an object x velocity at y degrees? I want to make my object go in random directions but at the same velocity? So can I choose a number 0 - 360, use the number to give my object a certain direction, and then give that object a certain velocity?

Thanks for any help

#5

You can do it like this:
 

local xSpeed = math.cos(degree\*math.pi/180) local ySpeed = math.sin(degree\*math.pi/180) obj:setLinearVelocity(xSpeed\*objSpeed, ySpeed\*objSpeed);

objSpeed is the general speed at which you would like the object to move (:

#6

Thanks! That seemed to do the trick. Just one thing. For the most part, the velocity of the object looks the same. However there is maybe like 1 in every 10 repetitions it looks a bit slower. Is this from the code or is just an illusion (going from top to bottom may look longer than going from side to side).

Thanks again!

#7

It should be an illusion :D, maybe given from the ratio width/height of the screen. I guess you can make sure of it if you place a background with a grid, might be easier to check if it’s going faster/slower (;

#8

Haha alright thanks again! :smiley:

#9

It is going to be extremely difficult to work out the object’s velocity from the applied force. I’ve been there - avoid it if you can. This is a Box2D thing and incredibly complex.

If you want to know what the velocity is, you should simply set it:

http://docs.coronalabs.com/daily/api/type/Body/setLinearVelocity.html

http://docs.coronalabs.com/daily/api/type/Body/angularVelocity.html

#10

Hey, thanks for the advice. Instead of using applyForce I used setLinerVelocity with my randomly generated numbers. However my object still has varying velocities. Do you know of a way that I could set a global velocity value and split that number into x and y components of varying values. Then randomly decide if each one is either positive or negative?

Thanks for the help!

#11

I still have had no luck. Is there any way to give an object x velocity at y degrees? I want to make my object go in random directions but at the same velocity? So can I choose a number 0 - 360, use the number to give my object a certain direction, and then give that object a certain velocity?

Thanks for any help

#12

You can do it like this:
 

local xSpeed = math.cos(degree\*math.pi/180) local ySpeed = math.sin(degree\*math.pi/180) obj:setLinearVelocity(xSpeed\*objSpeed, ySpeed\*objSpeed);

objSpeed is the general speed at which you would like the object to move (:

#13

Thanks! That seemed to do the trick. Just one thing. For the most part, the velocity of the object looks the same. However there is maybe like 1 in every 10 repetitions it looks a bit slower. Is this from the code or is just an illusion (going from top to bottom may look longer than going from side to side).

Thanks again!

#14

It should be an illusion :D, maybe given from the ratio width/height of the screen. I guess you can make sure of it if you place a background with a grid, might be easier to check if it’s going faster/slower (;

#15

Haha alright thanks again! :smiley: