Index: mesh_navmesh.c
===================================================================
--- mesh_navmesh.c	(revision 49732)
+++ mesh_navmesh.c	(working copy)
@@ -65,7 +65,56 @@
 
 #include "mesh_intern.h"
 #include "recast-capi.h"
+#include "DNA_group_types.h"
 
+// info: since this step is done for common objects and group objects I tried to extract a method so the code
+//       keeps nicer...but as soon as I have 2 group objects it dies. note sure what I'm doing wrong here.
+static void createObjectVertsTrisData(Object* ob, DerivedMesh* dm, float* verts, int* basenverts, int* tri) {
+
+	MVert *mvert;
+	int i, curnverts, curnfaces;
+	MFace *mface;
+	float co[3], wco[3];
+
+	curnverts = dm->getNumVerts(dm);
+	mvert = dm->getVertArray(dm);
+
+	/* copy verts */
+	for (i = 0; i < curnverts; i++) {
+		MVert *v = &mvert[i];
+
+		copy_v3_v3(co, v->co);
+		mul_v3_m4v3(wco, ob->obmat, co);
+
+		verts[3 * (*basenverts + i) + 0] = wco[0];
+		verts[3 * (*basenverts + i) + 1] = wco[2];
+		verts[3 * (*basenverts + i) + 2] = wco[1];
+	}
+
+	/* create tris */
+	curnfaces = dm->getNumTessFaces(dm);
+	mface = dm->getTessFaceArray(dm);
+
+	for (i = 0; i < curnfaces; i++) {
+		MFace *mf = &mface[i];
+
+		tri[0] = *basenverts + mf->v1;
+		tri[1] = *basenverts + mf->v3;
+		tri[2] = *basenverts + mf->v2;
+		tri += 3;
+
+		if (mf->v4) {
+			tri[0] = *basenverts + mf->v1;
+			tri[1] = *basenverts + mf->v4;
+			tri[2] = *basenverts + mf->v3;
+			tri += 3;
+		}
+	}
+
+	*basenverts += curnverts;
+
+}
+
 static void createVertsTrisData(bContext *C, LinkNode *obs, int *nverts_r, float **verts_r, int *ntris_r, int **tris_r)
 {
 	MVert *mvert;
@@ -73,6 +122,11 @@
 	MFace *mface;
 	float co[3], wco[3];
 	Object *ob;
+	GroupObject *gobj;
+
+	float mat4[4][4];
+
+
 	LinkNode *oblink, *dmlink;
 	DerivedMesh *dm;
 	Scene *scene = CTX_data_scene(C);
@@ -87,20 +141,48 @@
 	/* calculate number of verts and tris */
 	for (oblink = obs; oblink; oblink = oblink->next) {
 		ob = (Object *) oblink->link;
-		dm = mesh_create_derived_no_virtual(scene, ob, NULL, CD_MASK_MESH);
-		BLI_linklist_append(&dms, (void *)dm);
 
-		nverts += dm->getNumVerts(dm);
-		nfaces = dm->getNumTessFaces(dm);
-		ntris += nfaces;
+		// is it a group-instance?
+		if (ob->type == OB_EMPTY && ob->dup_group) {
+			Group *gr = ob->dup_group;
+			/* printf("group detected '%s'\n", gr->id.name+2); */
+			for (gobj = (GroupObject *)(gr->gobject.first); gobj; gobj = gobj->next) {
+				// create a function for this!?
+				dm = mesh_create_derived_no_virtual(scene, gobj->ob, NULL, CD_MASK_MESH);
+				BLI_linklist_append(&dms, (void *)dm);
 
-		/* resolve quad faces */
-		mface = dm->getTessFaceArray(dm);
-		for (i = 0; i < nfaces; i++) {
-			MFace *mf = &mface[i];
-			if (mf->v4)
-				ntris += 1;
+				nverts += dm->getNumVerts(dm);
+				nfaces = dm->getNumTessFaces(dm);
+				ntris += nfaces;
+
+				/* resolve quad faces */
+				mface = dm->getTessFaceArray(dm);
+				for (i = 0; i < nfaces; i++) {
+					MFace *mf = &mface[i];
+					if (mf->v4)
+						ntris += 1;
+				}
+				//-----
+
+			}
 		}
+		else {
+			// and reuse it here...same code! Yeah, sry! This could have been done better
+			dm = mesh_create_derived_no_virtual(scene, ob, NULL, CD_MASK_MESH);
+			BLI_linklist_append(&dms, (void *)dm);
+
+			nverts += dm->getNumVerts(dm);
+			nfaces = dm->getNumTessFaces(dm);
+			ntris += nfaces;
+
+			/* resolve quad faces */
+			mface = dm->getTessFaceArray(dm);
+			for (i = 0; i < nfaces; i++) {
+				MFace *mf = &mface[i];
+				if (mf->v4)
+					ntris += 1;
+			}
+		}
 	}
 
 	/* create data */
@@ -113,46 +195,111 @@
 	     oblink = oblink->next, dmlink = dmlink->next)
 	{
 		ob = (Object *) oblink->link;
-		dm = (DerivedMesh *) dmlink->link;
 
-		curnverts = dm->getNumVerts(dm);
-		mvert = dm->getVertArray(dm);
 
-		/* copy verts */
-		for (i = 0; i < curnverts; i++) {
-			MVert *v = &mvert[i];
+		// dupli-groups
+		if (ob->type == OB_EMPTY && ob->dup_group) {
 
-			copy_v3_v3(co, v->co);
-			mul_v3_m4v3(wco, ob->obmat, co);
+			Group *gr = ob->dup_group;
+							/* printf("group detected '%s'\n", gr->id.name+2); */
+			for (gobj = (GroupObject *)(gr->gobject.first); gobj; gobj = gobj->next) {
+				// actually this is more or less the same as for the common objects
+				// with the difference that additionally you have to apply the group-object-position and the object-position
+				// (hmm, there is something like an offset for group-instances?!..if yes, this needs to be done yet)
+				dm = (DerivedMesh *) dmlink->link;
 
-			verts[3 * (basenverts + i) + 0] = wco[0];
-			verts[3 * (basenverts + i) + 1] = wco[2];
-			verts[3 * (basenverts + i) + 2] = wco[1];
+				curnverts = dm->getNumVerts(dm);
+				mvert = dm->getVertArray(dm);
+
+				// combine positioning of the group-instance and the group-objects
+				mult_m4_m4m4(mat4,ob->obmat,gobj->ob->obmat);
+				/* copy verts */
+				for (i = 0; i < curnverts; i++) {
+					MVert *v = &mvert[i];
+
+
+					copy_v3_v3(co, v->co);
+					mul_v3_m4v3(wco, mat4, co);
+
+
+					verts[3 * (basenverts + i) + 0] = wco[0];
+					verts[3 * (basenverts + i) + 1] = wco[2];
+					verts[3 * (basenverts + i) + 2] = wco[1];
+				}
+
+				/* create tris */
+				curnfaces = dm->getNumTessFaces(dm);
+				mface = dm->getTessFaceArray(dm);
+
+				for (i = 0; i < curnfaces; i++) {
+					MFace *mf = &mface[i];
+
+					tri[0] = basenverts + mf->v1;
+					tri[1] = basenverts + mf->v3;
+					tri[2] = basenverts + mf->v2;
+					tri += 3;
+
+					if (mf->v4) {
+						tri[0] = basenverts + mf->v1;
+						tri[1] = basenverts + mf->v4;
+						tri[2] = basenverts + mf->v3;
+						tri += 3;
+					}
+				}
+
+				basenverts += curnverts;
+
+
+				if (gobj->next)
+					dmlink = dmlink->next;
+			}
 		}
+		// common objects with mesh
+		else {
+			// again the same code. hurts a bit in the eye. feel free to merge these to a function ;D
+			dm = (DerivedMesh *) dmlink->link;
 
-		/* create tris */
-		curnfaces = dm->getNumTessFaces(dm);
-		mface = dm->getTessFaceArray(dm);
+			curnverts = dm->getNumVerts(dm);
+			mvert = dm->getVertArray(dm);
 
-		for (i = 0; i < curnfaces; i++) {
-			MFace *mf = &mface[i];
+			/* copy verts */
+			for (i = 0; i < curnverts; i++) {
+				MVert *v = &mvert[i];
 
-			tri[0] = basenverts + mf->v1;
-			tri[1] = basenverts + mf->v3;
-			tri[2] = basenverts + mf->v2;
-			tri += 3;
+				copy_v3_v3(co, v->co);
+				mul_v3_m4v3(wco, ob->obmat, co);
 
-			if (mf->v4) {
+				verts[3 * (basenverts + i) + 0] = wco[0];
+				verts[3 * (basenverts + i) + 1] = wco[2];
+				verts[3 * (basenverts + i) + 2] = wco[1];
+			}
+
+			/* create tris */
+			curnfaces = dm->getNumTessFaces(dm);
+			mface = dm->getTessFaceArray(dm);
+
+			for (i = 0; i < curnfaces; i++) {
+				MFace *mf = &mface[i];
+
 				tri[0] = basenverts + mf->v1;
-				tri[1] = basenverts + mf->v4;
-				tri[2] = basenverts + mf->v3;
+				tri[1] = basenverts + mf->v3;
+				tri[2] = basenverts + mf->v2;
 				tri += 3;
+
+				if (mf->v4) {
+					tri[0] = basenverts + mf->v1;
+					tri[1] = basenverts + mf->v4;
+					tri[2] = basenverts + mf->v3;
+					tri += 3;
+				}
 			}
+
+			basenverts += curnverts;
+
 		}
-
-		basenverts += curnverts;
 	}
 
+
 	/* release derived mesh */
 	for (dmlink = dms; dmlink; dmlink = dmlink->next) {
 		dm = (DerivedMesh *) dmlink->link;
@@ -433,7 +580,9 @@
 
 	CTX_DATA_BEGIN (C, Base *, base, selected_editable_bases)
 	{
-		if (base->object->type == OB_MESH) {
+		if (base->object->type == OB_MESH
+				|| ((base->object->type == OB_EMPTY)
+						&& (base->object->transflag & OB_DUPLIGROUP) == OB_DUPLIGROUP && base->object->dup_group)) {
 			if (base->object->body_type == OB_BODY_TYPE_NAVMESH) {
 				if (!navmeshBase || base == scene->basact) {
 					navmeshBase = base;