Can anyone tell me why my collision detection does not work?

1

in my enemy class I create my rectangle like this.

enemyPos = new Vector2(spritePosX, spritetPosY);
 Rectangle enemyRect = new Rectangle((int)enemyPos.X - enemySprite.Width / 2,
     (int)enemyPos.Y - enemySprite.Height / 2, enemySprite.Width, enemySprite.Height);

they are updated like this.

enemyPos += heading * currentEnemySpeed;
 enemyRect.X = (int)enemyPos.X - enemySprite.Width / 2;
 enemyRect.Y = (int)enemyPos.Y - enemySprite.Height / 2;

and drawn

spriteBatch.Draw(enemySprite, enemyPos, null,
    Color.FromNonPremultiplied(255, spriteVarColor, 255, opacityVal),
    enemyOrientation, enemyRotOrigin, scale, SpriteEffects.None, 0f);

in the projectile class

spritePos = new Vector2(ProjectilePosX, ProjectilePosY);
 Rectangle projectileRect = new Rectangle((int)spritePos.X -
     projectileSprite.Width / 2, (int)spritePos.Y - projectileSprite.Height / 2,
     projectileSprite.Width, projectileSprite.Height);

and updated

spritePos = new Vector2(ProjectilePosX, ProjectilePosY);
projectileRect.X = (int)spritePos.X - projectileSprite.Width / 2;
projectileRect.Y = (int)spritePos.Y - projectileSprite.Height / 2;

ans drawn

spriteBatch.Draw(projectileSprite, spritePos, null,
    Color.FromNonPremultiplied(255, 255, 255, 255), spriteHeading,
    spriteRotOrigin, 1.0f, SpriteEffects.None, 0f);

then in the main game class i do this

foreach (Projectile projectile in projectiles)
{
    foreach (Enemy enemy in enemies)
    {
 
        if (projectile.ColRect.Intersects(enemy.ColRect))
        {
 
            projectile.Active = false;
            Exit();
            Constants.score += 1;

There are no collision detections. Can anyone tell me why? Is it because I have the rectangles as null in the draw method? Please help. :confused:

2

no idea, but to find the bug:

  1. I would render the collision rectangles so that I have a visual idea of what’s happenning.
  2. I’d put a breakpoint at if (projectile.ColRect.Intersects(enemy.ColRect)) and check what the values are there, and why they’re not passing the ‘if’
3

Are you changing scale when drawing the enemy? If it’s not 1.0 then you’ll need to scale enemyRect too for the math to match the visuals.

4

First thing: It is inefficient, but enough for small quantities of projectiles*enemies. Basically it should work the way you describe it.

Two things came into mind here (longshot, since code is incomplete) in addition to the already stated things:

  1. You’re telling us about projectileRect and enemyRect, yet you’re testing for projectile.ColRect and enemy.ColRect)…
  2. If you’re rotating sprites (I just infer that since you’re having a rotOrigin and the position is in the middle of the rectangles), then you’d have to create new axis-aligned-bounding-boxes (AABBs) since the rotation wouldn’t be taken into account (you’re just drawing the rotation)… but it should give you some collision in this case, just not ‘exact’…
5

I abandoned the rectangle collision approach and went to collision circle and everything worked like a charm. Thanks for the comments guys. :slight_smile:

6

Nice to hear you were able to solve it.
If you’re up for it you could take a step to the next level by installing some broad-phase collision detection to resolve collision-candidates before doing the narrow-phase collision detection.
After all n*m scales very badly :slight_smile:

Here is some stuff with sample code and nuget package ready to roll…

have fun

7

Thanks Bro! You’re a Pro! :ok_hand:

8

Lol…
No.
But virtually everyone else around here sure is.
:slight_smile: