Is there any way to tell if a shape collides with another shape im trying to make a simple game to test things. Im drawing circles with fillpie.

9 Years
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Last Post by atqamar

Simplest collision detection.
Circle to circle for 2D.
Sphere to Sphere for 3D

Radius of sphere???? (r)
Radius of Sphere A = rA
Radius of Sphere B = rB
Center position of Sphere A = vA
Center position of Sphere B = vB

You mentioned a circle, but for 2D or 3D but same principle applies.

Calculate distance between two points! (Pythagorean Thereom)

vD = vB - vA;

          vD.x = vB.x - vA.x
          vD.y = vB.y - vA.y
          vD.z = vB.z - vA.z       // If 3D

fDist = sqrt( (vD.x * vD.x) + (vD.y * vD.y) );                          // 2D
fDist = sqrt( (vD.x * vD.x) + (vD.y * vD.y) + (vD.z * vD.z) );  // 3D

So fDist is distance between the two points.

If distance between the two sphere centers is equal to rA + rB then you are touching. Less then that then you're merged!

So          if (fDist < rA+rB)          collided
             else if (fDist == rA+rB)  touching
              else                              not collision

If you have a lot of objects doing the square root takes time so instead do the distance calculation but skip the square root.
Then calculate but square the radius distance
r = rA + rB
r = r * r;

So now do the same comparison, but no need to spend processor time doing the square root operation.


There are many ways to optimize this, however, implementing those in script is difficult. Does anyone have any suggestions?

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