Question

I am trying to create a simple rigid body 2D physics engine.

I was able to create a rectangle image by using four lines and able to manipulate the image according to its angle and position; I can move and rotate it (though I made it possible to rotate I do not use the rotating function since I am unable to comprehend angular momentum theory yet).

The image will fall and bounce back based on simple formula:

v(velocity) += a(acceleration)
x += v(velocity)

But I have to click a button every time I want execute a movement.

I want it to execute itself automatically and update automatically, I tried to use loop but for some reason program seems to stop during the time it is in loop section. And because I use an infinite loop that will start over and over again, my program just freezes.

Not only this is the problem but also my good friend, who has better knowledge in physics, told me that I should be able to calculate the amount of time if I want to make this engine work properly.

Answer 1

I like DJ KRAZE’s comment – use a System.Windows.Threading.DispatcherTimer, and set the interval to however often you want the picture to redraw. On the timer’s Tick event, do your redraw.

If you want to know why the simple loop doesn’t work, you have to know a little bit about the Windows message loop. For a brief and somewhat inaccurate overview, all of stuff running in your application, it sounds like, is happening on one thread. Windows uses a message WM_PAINT, which goes through the message loop, to make the control paint itself. It only processes on message at a time.

Where you have your infinite loop, that is happening in the processing of some message. So this keeps the message loop from processing any messages, including messages for the controls to paint. So you don’t see anything updating in your infinite loop.