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Collision Detection + Classes

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Started by Robbie Woods May 05, 2012 05:47 PM

6 comments, last by frazchaudhry 11 years, 9 months ago

Robbie Woods

137

Author

May 05, 2012 05:47 PM

Hi guys. I'm making an asteroid clone using allegro following a tutorial. In the tutorial, he uses structs to make objects and puts the functions in main.cpp, but I've used classes to clean the code up a bit. He suggest using bounding box collision detection and I've followed how to do it but as I've used classes instead of structs, it doesn't work.

Here's my detection code:



void collideBullet(Bullet bullet[], int bSize, Comet comets[], int cSize)

{

for (int i = 0; i < bSize; i++)

{

  if (bullet.live)

  {

   for (int j = 0; j < cSize; j++)

   {

    if (comets[j].live)

    {

	 if (bullet.x > (comets[j].x - comets[j].boundX) &&

	  bullet.x < (comets[j].x + comets[j].boundX) &&

	  bullet.y > (comets[j].y - comets[j].boundY) &&

	  bullet.y < (comets[j].y + comets[j].boundY))

	 {

	  bullet.live = false;

	  comets[j].live = false;

	 }

    }

   }

  }

}

}

Everything else works in my game, apart from the comets don't disappear. Thanks.

alnite

3,454

May 05, 2012 05:56 PM

What's boundX and boundY? Are they width and height? If so, you collision should actually look like this:





		 if (bullet.x > (comets[j].x) &&

		  bullet.x < (comets[j].x + comets[j].boundX) &&

		  bullet.y > (comets[j].y) &&

		  bullet.y < (comets[j].y + comets[j].boundY))

		 {

		  bullet.live = false;

		  comets[j].live = false;

		 }

Robbie Woods

137

Author

May 05, 2012 06:11 PM

boundX and boundY are the bounding box of the comet.

Robbie Woods

137

Author

May 05, 2012 11:52 PM

I tried your suggestion but it didn't work :/

alnite

3,454

May 06, 2012 01:34 AM

boundX and boundY are the bounding box of the comet.

Then you need the width and height of the bounding box.

		 if (bullet.x > (comets[j].boundX) &&

		  bullet.x < (comets[j].boundX + comets[j].boundWidth) &&

		  bullet.y > (comets[j].boundY) &&

		  bullet.y < (comets[j].boundY + comets[j].boundHeight))

kruncher

354

May 10, 2012 04:38 PM

I do not understand the specifics of your game, but surely wouldn't circular collision be more appropriate for a comet?

I am guessing that you are using C# from the syntax (not tested, but looks right):

[font=courier new,courier,monospace]



void collideBullet(Bullet bullet[], int bSize, Comet comets[], int cSize) {

   // change to meet your needs

   float bulletRadius = 3.0f;



   for (int i = 0; i < bSize; i++) {

	  if (bullet.live) {

		 for (int j = 0; j < cSize; j++) {

			if (comets[j].live) {

               // Calculate distance from origins

			   float distanceBetween = Math.Sqrt(

					 Math.Pow(bullet.x - comets[j].x, 2.0f) +

					 Math.Pow(bullet.y - comets[j].y, 2.0f)

				  );

			   // Remove radius of bullet and comet to get inner distance

			   distanceBetween -= bulletRadius + comets[j].radius;



			   // Touching or overlapping?

			   if (distanceBetween <= 0.0f) {

				  bullet.live = false;

				  comets[j].live = false;

			   }

			}

		 }

	  }

   }

}

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littletray26

284

July 04, 2012 01:56 AM

I've followed how to do it but as I've used classes instead of structs, it doesn't work.

FTR: C++ Structs and Classes are, for the most part, identical. Therefore there is something else causing your code to fail

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frazchaudhry

1,220

July 04, 2012 04:42 AM

[quote name='Shenaynay' timestamp='1336240037' post='4937638']
I've followed how to do it but as I've used classes instead of structs, it doesn't work.

FTR: C++ Structs and Classes are, for the most part, identical. Therefore there is something else causing your code to fail
[/quote]

yup structs and classes are inherently the same thing. The only difference being that the members and methods of a class are private by default and public in the case of structs. If your object does not disappear you might wanna check the part of the code responsible for drawing the object to the screen, and once the object is no longer "live" do not draw it to the screen. Maybe that's the issue can't tell without looking at the rest of the code.

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