Android Open Source - RollOverSphere---a-simple-libgdx-game Collision Helper

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License

The source code is released under:

MIT License

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Java Source Code

package com.igorcrevar.rolloverchuck.utils;
//w  w  w  .  j a v  a 2 s. c o  m
import com.badlogic.gdx.math.Vector2;
import com.badlogic.gdx.math.Vector3;

public class CollisionHelper {
  private static Vector2 segmentV = new Vector2();
  private static Vector2 ptV = new Vector2();
  private static Vector2 tmpV2 = new Vector2();
  private static Vector2 closestPointOnSegment(Vector2 segA, Vector2 segB, Vector2 circleCenter) {
    segmentV.set(segB).sub(segA);
    ptV.set(circleCenter).sub(segA);
        float segmentVLen = segmentV.len();
        if (segmentVLen == 0f) {
          throw new IllegalArgumentException("segA == segB for closestPointOnSegment");
        }
        
        Vector2 segVUnit = segmentV.scl(1 / segmentVLen);
        float proj = ptV.dot(segVUnit);
        if (proj <= 0f) {
          return segA;
        }
        if (proj >= segmentVLen) {
          return segB;
        }
        
        segVUnit.scl(proj).add(segA);
        return segVUnit;
   }

   public static boolean intersection(Vector2 segA, Vector2 segB, Vector3 circleCenter, float circleRadius) {
    tmpV2.set(circleCenter.x, circleCenter.z);
    return intersection(segA, segB, tmpV2, circleRadius);
   }
  
   public static boolean intersection(Vector2 segA, Vector2 segB, Vector2 circleCenter, float circleRadius) {
    Vector2 closest = closestPointOnSegment(segA, segB, circleCenter);
    tmpV2.set(circleCenter); // for god sake
    tmpV2.sub(closest);
    float len = tmpV2.len();
    if (len > circleRadius) {
      return false; // no collision
    }
    if (len == 0) {
      return false;
    }
    
    return true;
     /*closest = closest_point_on_seg(seg_a, seg_b, circ_pos)
    dist_v = circ_pos - closest
    if dist_v.len() > circ_rad:
      return vec(0, 0)
    if dist_v.len() <= 0:
      raise ValueError, "Circle's center is exactly on segment"
    offset = dist_v / dist_v.len() * (circ_rad - dist_v.len())
    return offset*/
   }
  
}

Java Source Code List