You could assign points to the black rectangle...

A cleaner, all-around more substantial solution would involve using an off-screen PGraphics object. This approach is used by professional game developers and others... and, although it may be beyond the scope of the problem, I feel like describing it...

You have to draw everything that shows up on the screen in the PGraphics object, and each object should have its own color. If you give the objects transparency, then you can find overlapping objects by the new colors that are formed.

Calsign thank you for your reply.

I do not really know what PGraphics object is but I am going to check it to see if it helps.

Let me give you some more info about my program..

The program I am doing is a simple game and I have a craft that fires bullets..

Now the things are simple .. The stage consists of black and white shapes.. where the black are the obstacles..

The bullets are kept in an ArrayList..

When I fire a bullet, a function inside the bullet checks if the color is black and if this is the case, the bullet is removed..


A new need came up.. I want to fire bullets against enemies.. The enemies probably are going to be kept in an ArrayList.. Based on the same philosophy I can check if the bullet overlaps in an object of color of the enemy.. and so I can remove the bullet..

What I cannot really figure out is how to tell which enemy was hit by that bullet..


The only solution that I have not tested yet is to have some kind of getters to get the x,y of 3-4 points of each enemy.. When a bullet hits somewhere, I check if it is an enemy and then I check if the x,y of the bullet is within the range of the x,y of the enemy..

I do NOT like this solution for two reasons:
1) If the enemy hasn't the shape of a rectangle the equations are much harder to implements correctly
2) I have to have a function in each enemy that checks if a bullet is in the same area as itself..

Any thoughts?


Thanks!

You have a bounding box solution... most of the time, a simple bounding box is enough, as users won't be able to notice at a high frame rate. Instead of just using four points, however, you could use the entire border, or even a border of a couple of pixels...

When you have two arrays / lists of objects that you want to collision detect (it's a verb, now?), it's simple to create a nested for loop looping through every object...

Collision detection is a popular topic in general. For more ideas, you can search on the main site.