Clicking on 3d object - positon of click on object

Troubleshooting General Help
1

Hi, I am trying to make 3d strategy game. I am using mouse to click on gameboard, but problem is that i cant determine where I am clicking on board, all I can get is possition of cursor on screen. I guess theres some equation, but cant find it or make it out. Or perhaps theres some function?

Any help is appreciated.

2

you need to cast a ray into the scene and check the intersections…

here's some code to find triangle intersection with a ray…


final  static  public  TrianglePickData    findClosestTriangle(Ray cl_ray, Spatial cl_testAgainst) {
   TrianglePickResults        lcl_pick = new TrianglePickResults();
   lcl_pick.setCheckDistance(true);
   cl_testAgainst.findPick(cl_ray, lcl_pick);

   if(lcl_pick.getNumber() == 0) {
      return null;
   }

   float       lf_distance = Float.MAX_VALUE;
   int         li_lowestIndex = -1;

   for(int li_index = 0; li_index < lcl_pick.getNumber(); li_index++) {
      TrianglePickData        lcl_data = (TrianglePickData)lcl_pick.getPickData(li_index);
      if(lcl_data.getDistance() < lf_distance) {
         lf_distance = lcl_data.getDistance();
         li_lowestIndex = li_index;
      }
   }

   if(li_lowestIndex == -1) {
      return null;
   }

   return (TrianglePickData)lcl_pick.getPickData(li_lowestIndex);
}



you would use it then like this...


Vector2f      lcl_pt = new Vector2f(MouseInput.get().getXAbsolute(), MouseInput.get().getYAbsolute());
Vector3f lcl_worldNear = DisplaySystem.getDisplaySystem().getWorldCoordinates(lcl_pt, 0);
Vector3f lcl_worldFar = DisplaySystem.getDisplaySystem().getWorldCoordinates(lcl_pt, 1);

Ray lcl_ray = new Ray(lcl_worldNear, lcl_worldFar.subtractLocal(lcl_worldNear).normalizeLocal());

TrianglePickData        lcl_p = findClosestTriangle(lcl_ray, rootNode);

if(lcl_p == null) {
    System.out.println("no sel");
    return;
}

if(lcl_p.getTargetMesh() instanceof TriMesh) {
    TriMesh     lcl_mesh = (TriMesh)lcl_p.getTargetMesh();
    System.out.println("sel = " + lcl_mesh.getName());
}


3

Thanks a lot! thats exactly what i was looking for