CODEWITHSUNDEEP
android2dcollision-detection
carefacerz
carefacerz

Reputation: 1297

Android Development: Simplest collision detection?

I'm trying to accomplish collision detection. Im not using OpenGl, I'm using canvas/surfaceview.

I have 2 bitmaps. This is what ive come up to so far:

public boolean inBounds(int x2,int y2, int x,int y,int width,int height){
    if(x2 > x && x2 < x + width -1 && y2 > y && y2 < y + height -1){
        return true;
    }
     return false;

       }

This does run but it only detects collision if x2 and y2's corner is inside the other object.

So how do I improve my collision detection?

enter image description here

This image I found on the web should detect collision in my program.

//Simon

Upvotes: 2

Views: 2862

Answers (4)

pthomaid
pthomaid

Reputation: 177

The android.graphics.Rect class contains some nice functions to do this in one line. You can check out intersect.

Upvotes: 0

user1140237
user1140237

Reputation: 5045

To detect Rectangle Collission

bool isIntersect(Rectangle a, Rectangle b){
    return a.Left < b.Right && a.Top < b.Bottom &&
           b.Left < a.Right && b.Top < a.Bottom;
}

For Two Circle Collission Detection

bool isIntersect(Circle a, Circle b)
{ 
Vector<ClassWithLengthRadiusProp> vDistanceProp = a.Center - b.Center;
    return vDistanceProp.Length < a.Radius + b.Radius;
}

OR(Accurate With Sqrt)

bool isIntersect(Circle a, Circle b)
{
   Vector<ClassWithLengthRadiusProp> vDistanceProp = a.Center - b.Center;
    float radiusSum = a.Radius + b.Radius;
    float squaredDistanceLength = vDistanceProp .x * vDistanceProp .x +
                                  vDistanceProp .y * vDistanceProp .y;

    return squaredDistanceLength < radiusSum * radiusSum;
}

Upvotes: 1

pqn
pqn

Reputation: 1532

If they are circles then here's a little pseudo code for you:

if (Math.sqrt(Math.pow(bitmap1.centerX-bitmap2.centerX, 2) + Math.pow(bitmap1.centerY-bitmap2.centerY, 2))<=bitmap1.width) 
    return true;
else
    return false;

Since you now want rectangles (and assuming they're different sizes):

if (Math.abs(bitmap1.centerX-bitmap2.centerX)<=(bitmap1.width+bitmap2.width)/2f
    && Math.abs(bitmap1.centerY-bitmap2.centerY)<=(bitmap1.height+bitmap2.height)/2f)
    return true;
else
    return false;

Hope that helps!

Upvotes: 2

Chris
Chris

Reputation: 1766

if(r1.lowerLeft.x < r2.lowerLeft.x + r2.width 
   && r1.lowerLeft.x + r1.width > r2.lowerLeft.x 
   && r1.lowerLeft.y < r2.lowerLeft.y + r2.height 
   && r1.lowerLeft.y + r1.height > r2.lowerLeft.y)
   return true;

   else
   return false;

That should do it unless you want to do a circle collision detection. r1 & r2 and defined as Rects

Upvotes: 0

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