moving items in JPanel

Question

I am working on a pong game and I am working on the mechanism to move the ball. If I add 1 to x the ball moves 1 pixel to the right, if i add 1 to y the ball moves 1 pixel to the bottom. What if I want to move the ball at a certain angle how can 1 calculate the coordinates.

Answer 1

you are looking for line drawing algorithms, something like Bresenham or DDA you can find some reasonable implementations here ofcourse instead of drawing a complete line you would move your ball along that line but the way of finding the set of lines to move on is the same.

Answer 2

You might find these resources helpful.

Answer 3

for something like Pong you should be investigating vector math, but if all you want is to know an angle all you really need is SOHCAHTOA.

Answer 4

Trying to work with angles will get a bit more complicated than you need to get. For this kind of animation you generally want to use floats to store your objects x and y coordinates and move it by applying x and y deltas (The floats will preserve the detail of the position which is lost to rounding when drawn on the screen). The deltas represent the speed your object is moving in each axis and can be negative or positive.

For each iteration of your animation, add xdelta to your x coordinate and add ydelta to your y coordinate. Round them off to position them on the screen.

When you hit the top or bottom border, you would swap the sign on your ydelta component and likewise for side borders.

You wouldn't want to keep the same x and y delta all the time so when the objects hits a paddle, modify the x or y delta a little bit to change up the angle.