--- ray/src/rt/pmapamb.c	2015/02/24 19:39:26	2.1
+++ ray/src/rt/pmapamb.c	2015/08/18 18:45:55	2.6
@@ -1,13 +1,17 @@
+#ifndef lint
+static const char RCSid[] = "$Id: pmapamb.c,v 2.6 2015/08/18 18:45:55 greg Exp $";
+#endif
 /* 
    ==================================================================
    Photon map interface to RADIANCE ambient calculation
 
    Roland Schregle (roland.schregle@{hslu.ch, gmail.com})
    (c) Fraunhofer Institute for Solar Energy Systems,
-       Lucerne University of Applied Sciences & Arts
+   (c) Lucerne University of Applied Sciences and Arts,
+   supported by the Swiss National Science Foundation (SNSF, #147053)
    ==================================================================   
    
-   $Id: pmapamb.c,v 2.1 2015/02/24 19:39:26 greg Exp $
+   $Id: pmapamb.c,v 2.6 2015/08/18 18:45:55 greg Exp $
 */
 
 
@@ -57,8 +61,9 @@ int ambPmapCaustic (COLOR aval, RAY *r, int rdepth)
    /* Handle precedence in case of multiple photon maps: contrib > caustic */
    PhotonMap *pmap = contribPhotonMapping ? contribPmap : causticPmap;
 
-   /* Get caustic photon density estimate only at primary rays */
-   if (pmap && !rdepth) {
+   /* Get caustic photon density estimate at primary rays or when
+    * filling in ambient rays that have no global photon map to use */
+   if (pmap && (!rdepth || !globalPmap & !contribPmap & !preCompPmap)) {
       /* Temporarily factor ambient value into ray coefficient
        * (required for contribution photon map) */
       copycolor(rcoef, r -> rcoef);