code: public void setFrustum(Matrix4f projMatrix)
      {
          if (projMatrix != null)
          {
              if (mProjMatrix == null)
              {
                  mProjMatrix = new float[16];
              }
              mProjMatrix = projMatrix.get(mProjMatrix, 0);
              mScene.setPickVisible(false);
              if (mCuller != null)
              {
                  mCuller.set(projMatrix);
              }
              else
              {
                  mCuller = new FrustumIntersection(projMatrix);
              }
          }
          mProjection = projMatrix;
      }
docs: Set the view frustum to pick against from the given projection  matrix.
  
  If the projection matrix is null, the picker will revert to picking
  objects that are visible from the viewpoint of the scene's current camera.
  If a matrix is given, the picker will pick objects that are visible
  from the viewpoint of it's owner the given projection matrix.
  
  @param projMatrix 4x4 projection matrix or null
  @see GVRScene#setPickVisible(boolean)