CODEWITHSUNDEEP
c#xnaxna-4.0
PepperTheDog
PepperTheDog

Reputation: 43

How do I check for an object at a certain position?

I have a black targetBox that is used to check the area it covers for the existence of Block objects such as the grey one in the top left hand corner and return a boolean if there is a Block at that position. It's a tile system and I have included one case where it would return "false" and one that would return "true".

This would return false

This would return true

I understand I can do something like

public bool checkTargetObjects()
{
    if(block.x == target.x && block.y == target.y) 
    {
        return true;
    }
    else
    {
    return false;
    }
}

But I am unsure of how to look for Block objects at the position. How can I do this?

Upvotes: 2

Views: 2041

Answers (2)

Pierre-Luc Pineault
Pierre-Luc Pineault

Reputation: 9201

Instead of storing the X and Y position of your tiles, save that data as a Rectangle. The only additional thing you need is the Width and Height of your tiles (which should be a constant somewhere).

So instead of having 

public class Block 
{
    public int X { get; set; }
    public int Y { get; set; }
}

you can have

public class Block 
{
    public Rectangle Area { get; set; }
}

Then you can take all your blocks (Let's say you got them all in a List<Block> called blocks) and iterate over them to see which one intersects with your Target :

var blocksInTarget = blocks.Where(b => b.Area.Intersects(target.Area));

where Area is your rectangle.

If you only want to know if there is a rectangle (and not which ones), you can change that Where with Any, which you can read as "Return true if there is any block intersecting my target" :

bool isBlockPresent = blocks.Any(b => b.Area.Intersects(target.Area));

Upvotes: 2

JosephDoggie
JosephDoggie

Reputation: 1594

You can create a compare double function like

  const THRESH = 1e-3; // define as desired for your application
   public bool compareDoubles(double a1, double a2)
   {
      if( fabs(a1-a2) < THRESH)
          return true;
     else
          return false;
   }

This allows for a tolerance from getting ONLY exact matches, which are rare for dobules! Then you would use the function on the x and y dimensions of each object (and z if anyone is using 3D). you could even make THRESH a parameter if there is a significant difference in the tolerance on a per dimension basis.

Upvotes: 0

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