Ball bouncing effect

[NikG]

Something I was just playing with... a ball falling and bouncing off the bottom of the screen. I tried to simulate friction and gravity.

code:

View.Set ("offscreenonly") var BallX := 50.0 var BallY := 200.0 %starting ball height var maxBallY := BallY var newVelMplr := 0.069 %0.068 to 0.075 var VelX := 2.5 var VelY := 0.0 var Gravity := -0.6 %good values from -0.49 to -0.71 var Friction := -0.09 loop     BallX += VelX     BallY += VelY     if BallY > maxBallY then         maxBallY := BallY     end if     VelY += Gravity     if round (BallY) <= 12 then         VelY := maxBallY * newVelMplr         maxBallY := 0         if VelX > 0 then             VelX += Friction         end if     end if     drawfilloval (round (BallX), round (BallY), 10, 10, green)     View.Update     exit when VelX <= 0     delay (20)     drawfilloval (round (BallX), round (BallY), 10, 10, white) end loop

Anything wrong with this approach?

[blaster009]

Looks fine to me!

[upthescale]

Cool man nice effect

[Darkmantis]

This is awesome! I've been trying to figure this out for so long, Yay my search is over !

[Remm]

thats awsome; you should put somthing in so you can drag it up 'n drop it.

[Aziz]

Good. Gravity is 9.8 though, in physics Just playing, it's nice. Shouldn't be hard to convert to drag-and-drop.

[TheOneTrueGod]

Yarr, what people don't realise is that gravity is 9.8 metres / second Code doesn't work in metres per second, it works in pixels per loop execution. You could do some calculations to convert it, but for a simple effect like this, it isn't worth it

Also, the diminishing returns (I believe thats what its called) of the ball's movement doesn't work the way you have it. It should be something more along the lines of

code:

%Pseudo Code if the ball hits the ground then     ball's yspeed *= -0.9 %Or some other value that is approximately = 1 end if This way, the ball's speed is adjusted properly. Other than that, nice work.  This is the simplest application of vector movement, but its a good example to refer back to when the more complicated stuff fails ya. :P

[Aziz]

Yeah, I realized that. Figured that. And tried it. It just goes flump. You'd have to make a scale (1 metre = 50 px?) and then could would work

[TheOneTrueGod]

1 metre for 50 pixels? wow dude, my monitor is 1200 pixels across, and its not even half a metre. Depending on your resolution, the scale would have to be different, so that it would work on all computers. You'd have to set the screensize to max/max, you would have to KNOW the dimensions of their monitor, and not to mention the fact that g is not a constant, and it changes as your distance from the earth changes. Also, just converting it from metres to pixels doesn't work either, because you still have to convert time to a relative one. You would have to know the frames per second that your program is operating at, then you would have to factor that into the conversion. Theres a lot more to think about than just plugging in the value of 9.8 and assuming itll work . In my experiences, (using my formulae, though) the best g to work with is one of 0.3-0.5.

[Aziz]

Lol, no, sorry if I didn't clarify, I meant using a scale to represent 1 metre as 50 pixels (like you would do on a graph. Such as 'let 1cm represent 1m'). And the value of g isn't constant, you're right, but it's basically irrelevant to include to difference for this purpose Then again, it's irrelevant to put this into terms of real physics, too When it's so much easier to just do it so it works out . I was just experimenting, as yours/his method is *muchos* more effecient. But hey, >_> I always think of those "hey I wonder how we could do that..." thinks. Then I get worked up and can't sleep (generally I think about these things while lying in bed lol)

[sylvester-27]

actually the maximum velocity for objects falling to earth is 9.81 m/s. ya the ball falling thing is pretty good

[Aziz]

sylvester-27 wrote:

actually the maximum velocity for objects falling to earth is 9.81 m/s. ya the ball falling thing is pretty good

You mean acceleration Acceleration due to gravity is 9.8m/s^2. Velocity for a falling object at any given time is HEIGHT - 9.8 * TIME (given the object started at rest) Wow, why are we debating physics?

[NikG]

I tried adding the Mouse drag code and it works for the most part:

code:

View.Set ("offscreenonly") var x, y, b, b2 : int var BallInHand := false var BallInMotion := true var BallX := 50.0 var BallY := 200.0 %starting ball height var maxBallY := BallY var newVelMplr := 0.068 %0.068 to 0.075 var VelX := 2.0 var VelY := 0.0 var Gravity := -0.6 %good values from -0.49 to -0.71 var Friction := -0.11 loop     Mouse.Where (x, y, b)     if Mouse.ButtonMoved ("down") and Math.Distance (x, y, BallX, BallY) <= 10 then         Mouse.ButtonWait ("down", x, y, b, b2)         BallInHand := true     elsif Mouse.ButtonMoved ("up") and BallInHand then         Mouse.ButtonWait ("up", x, y, b, b2)         BallInHand := false         BallInMotion := true         maxBallY := y         VelX := 2         VelY := 0     elsif Mouse.ButtonMoved ("downup") then         Mouse.ButtonWait ("downup", x, y, b, b2)     end if     if BallInHand then         BallX := x         BallY := y     else         if BallInMotion then             VelY += Gravity             BallX += VelX             BallY += VelY             if BallY > maxBallY then                 maxBallY := BallY             end if             if round (BallY) <= 30 then                 if VelX > 0 then                     VelY := maxBallY * newVelMplr                     maxBallY := 0                     VelX += Friction                 else                     BallInMotion := false                 end if             end if         end if     end if     drawline (0, 20, maxx, 20, black)     drawfilloval (round (BallX), round (BallY), 10, 10, green)     View.Update     delay (35)     drawfilloval (round (BallX), round (BallY), 10, 10, white) end loop

There are a few problems though... for some reason, the ball seems to jump higher if you drop it from too high, and I still haven't gotten a good feel for friction.

[_justin_]

wow man thats pretty awesome real nice work keep it up

[sylvester-27]

dunno, we just finished the Motion unit of gr 10 science. i can't believe i said maximum velocity. i think like the max v for a human is like 200 km/h.