1. Collision detection?

Sorry if this sounds like a stupid question, but I was just wondering what
collision detection was.  If anyone knows, I'd like some information on the
subject.

I was also wondering if there was a way in Euphoria of displaying images on the
screen (display_image()) that would merge images and backgrounds (like Qbasic's
XOR or AND).

Thanks in advance.



       __    ___       __    ___       ___
      /_/|  /__/\     /_/|  /__/\     /__/|
      | ||  |   \\    | ||  |   \\   /   ||
      | ||  | |\ \\   | ||  | |\ \\ /    ||
      | ||  | ||\ \\  | ||  | ||\ \/ /|  ||
 _    | ||  | || \ \\ | ||  | || \  //|  ||
/_/\__| ||  | ||  \ \\| ||  | ||  \// |  ||
\ \/__/ //  | ||   \ \| ||  | ||      |  ||
 \_____//   |_|/    \___||  |_|/      |__|/

                Joshua N. Milligan
              silverlaser at HoTMail.com

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2. Re: Collision detection?

On Wed, 9 Apr 1997, Joshua Milligan wrote:
>
> Sorry if this sounds like a stupid question, but I was just wondering what
> collision detection was.  If anyone knows, I'd like some information on the
> subject.

Collision detection is DETECTING if things are COLLIDING.  A collision is
when parts of two or more objects try to occupying the same space at the
same time, like when two cars hit each other, or when a ball its a wall.
In computer graphics, it's when the Area Of Interest of image 1 overlaps
the Area of Interest of image 2 on the screen.  If you don't want that to
happen, say you want to explode your ship when it hits an oid, you need to
do some sort of collision detection every once in awhile to see if they
are colliding, then do something about it.

I say Area of Interest (AoI) of the images, since usually the image is
bigger than the part your interested in colliding with something.  You
animate with rectangular images, but your ship, say doesn't completely
fill the rectangle, so you pick a smaller AoI that closer corresponds to
your ship.  Sometimes you want to have part of your objects overlap before
you blow them up.

To actually check for a collision, an easy way is to check the upper left
and lower right x,y coordinates of the AoI of object 1 and see either of
them are inside the AoI of object 2, then do the same with object 2.


Michael Packard
Lord Generic Productions
lgp at exo.com http://exo.com/~lgp
A Crash Course in Game Design and Production
http://exo.com/~lgp/euphoria

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