shooting bullets - transition.to versus applyLinearImpulse

Physics
#1

Heyho :slight_smile:

I have a little prototype game with box2d physics activated. in my game there is a player that shoots bullets where every bullet has a “dynamic” physics body to detect collision with other objects. in a later stage of my game there will probably be a lot of bullets flying around on the screen. now there are two implementations I thought about:

local BulletClass = {} function BulletClass.new(stage, xPos, yPos) local bullet = display.newCircle(xPos, yPos, 5) stage:insert(bullet) physics.addBody( bullet, "dynamic", {density=1, friction=0, bounce=0, radius = 5 } ) bullet.isBullet = true camera:add(bullet, 2) bullet.speedPerSecond = 400 bullet.distance = 200 bullet.name = "bullet" function bullet.shoot(toXPos, toYPos, withPhysics) if withPhysics then local vector = utils.getDirection(toXPos - xPos, toYPos - yPos, 1) bullet:applyLinearImpulse(vector.x\*1, vector.y\*1, xPos, yPos) timer.performWithDelay( 2000, function() display.remove(bullet) end, 1) else local vector = utils.getDirection(toXPos - xPos, toYPos - yPos, bullet.distance) local travelTime = (bullet.distance / bullet.speedPerSecond) \* 1000 transition.moveBy( bullet, { time = travelTime, x = vector.x, y = vector.y, onComplete = function() display.remove(bullet) end} ) end end return bullet end return BulletClass

the important part is inside the shoot function where I can switch between a physics version and a transition version. I would like to use the physics version because it is easier to implement bouncing bullets or things like that in the future. but with a lot of bullets on the screen I am afraid that I will see huge fps drops due to a lot more calculations compared to the transition.to version of my bullet. how much more does the applyLinearImpulse version cost me?

grettings

gritob :slight_smile:

#2

If you’re asking what the performance impact would be with the physics implementation, you would be the only way possible to judge. You would need to gauge how many bullets can be on screen and being acted on by physics before you saw a FPS drop, and this would likely be drastically different between devices between operating systems.

FWIW I have modeled my projectile logic around physics and it works fine on most modern devices.

#3

Here’s the link to my github for physics projectile logic. I don’t do much commenting but it should be relatively straightforward.

#4

If you’re asking what the performance impact would be with the physics implementation, you would be the only way possible to judge. You would need to gauge how many bullets can be on screen and being acted on by physics before you saw a FPS drop, and this would likely be drastically different between devices between operating systems.

FWIW I have modeled my projectile logic around physics and it works fine on most modern devices.

#5

Here’s the link to my github for physics projectile logic. I don’t do much commenting but it should be relatively straightforward.