code: package org.sunflow.core;
  
  import org.sunflow.image.Color;
  import org.sunflow.math.Point3;
  import org.sunflow.math.Vector3;
  
  /**
   * Represents a global photon map. This is a structure which can return a rough
   * approximation of the diffuse radiance at a given surface point.
   */
  public interface GlobalPhotonMapInterface extends PhotonStore {
  
      /**
       * Lookup the global diffuse radiance at the specified surface point.
       * 
       * @param p surface position
       * @param n surface normal
       * @return an approximation of global diffuse radiance at this point
       */
      public Color getRadiance(Point3 p, Vector3 n);
  }