Another q. about time based movement

Redoc · 2003-05-02T22:43:46

Hi there!, I hope you can help me Im trying to get the hang of movement of time, instead of movement of frames. To begin with I made a test application, this holds a variable of the sprites speed. float Speed = 300; and I made a slow down rate for this object float SlowRate = 0.96; I calculate the time each frame took, known as TimeElapsed but I dont know what to do with it, its calculation is 17. Inside my main loop I apply the slow down to the speed as so: Speed = Speed * SlowRate; I measured the amout of time this takes to reach 0, at 60 FPS it takes just over 3 seconds. After that test I added a Sleep(30); in to the main loop reducing the FPS to 20 and this time it took just over 9 seconds for Speed to reach 0 So it must be something so simple I am missing Anyone available to help me? I want to make Speed reach 0 at the same rate no matter what the FPS is. Thanks I hope I made everything clear! [edited by - redoc on April 30, 2003 4:53:14 AM]

Math and Physics Programming

Started by Redoc April 30, 2003 03:51 AM

15 comments, last by Redoc 20 years, 11 months ago

Redoc

122

Author

May 01, 2003 05:58 AM

Airo: Thanks, would that work on negative speeds though? Just a thought..

AP: thanks for that too! Im not sure why PI is in the formulae, what is ''e'' for?

And about this:

x = x * (e ^ (k * t))

This is just my version I can read better, I want to see if that read the same as the formulae Sneftel has (I dont know how to make the floaty letters / numbers

)

Thanks again

Anonymous

May 01, 2003 06:25 AM

you should be careful with x subscript 0, it is different to x. (x sub 0 is a constant)

Anonymous

May 01, 2003 06:29 AM

e is an un-natural number made up by mad scientist.

Anonymous

May 01, 2003 06:37 AM

quote:Original post by Anonymous Poster
Secondly e does not equal 2.71... it is infact 3.14... I''m sure everyone will agree on this point too.

Yeah, I''m sure they will...

Anonymous

May 01, 2003 07:01 AM

pi/pi = 1
e/e = 1,
thus it stand to reason pi = e

brassfish89

122

May 02, 2003 05:56 PM

quote:
maybe you could use a different approach?

like speed += acceleration*time-elapsed;

i agree. here is an example:

  double last_frame=/*time last frame*/;double this_frame=GetTickCount();double delta=this_frame-last_frame;double x=0.0f,y=0.0f;// speed==amount of pixels you want to move// in a secondint speed=300;x+=((float)delta/1000)*speed;

doh, nuts. Mmmm... donuts
My website

Redoc

122

Author

May 02, 2003 10:43 PM

Thanks for all the messages so far.

Brassfish, I know how to speed my object up

I need to know how to slow it down naturally.. What I have done to slow the sprite down works exactly how I want it here:

float SlowRate = 0.96;

// each frame aceleration is added (Speed += Aceleration * FrameTime)
// then to slow down I have
Speed = Speed * SlowRate;

BUT, on fast computers the speed slows very FAST and on slow computers it slows slower. I want to adapt that formulae to reach 0 no matter what FPS is at.

Does that make sense? I hope it does. thanks

Another q. about time based movement

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Another q. about time based movement

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