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[java] J2ME: Thrust and Gravity...

Started by RageMatrix Feb 25, 2005 at 4:58 AM 1 replies 850+ views

Original Post

Feb 25, 2005 at 4:58 AM

I'm trying to implement the following and have no real idea on how to do this, especially because of the lack of floating point under J2ME MIDP1.0 and also because my math sucks. What I want to do is have a sprite at the bottom of the screen that when you press UP thrusts into the air up the Y axis up to a maximum acceleration. When letting go of the UP button, I'd like him to fall back down again until he either hits a platform or the "ground" which is (getHeight()). Any pointers, hints, advice on how to achieve this? This is actually (from my point of view) the hardest part of my game.....after this, its plain sailing. Thanks.

Skizz

Feb 25, 2005 at 5:26 AM

Use fixed point maths. You will need to be very careful with the range of values you use - it can be very easy to overflow the fixed point range. Search google/gamedev for fixed point - it has been covered a lot.

Skizz

Thygrrr

Feb 28, 2005 at 10:56 AM

You can also just add integer values to integer velocities to represent acceleration. Increase the speed by 1 every 100 ms: Voila, pretty close to an acceleration of 9.81 units per second squared.

But fixed point is the bestway to go. Very easy, fairly efficient, and a lot of fun to use!

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