diff --git a/samples/tcl/pathtrace.tcl b/samples/tcl/pathtrace.tcl
index 713295a370..670b4ce85d 100644
--- a/samples/tcl/pathtrace.tcl
+++ b/samples/tcl/pathtrace.tcl
@@ -1,51 +1,51 @@
-#########################################################################
-# 26437: Visualization - Improve path tracing rendering engine
-#########################################################################
+# Script demonstrating Global illumination effects using non-interactive 
+# path tracing rendering engine in 3d view
 
-pload ALL
+#Category: Visualization
+#Title: Path tracing
+
+pload MODELING VISUALIZATION
 
 # setup 3D viewer content
 vinit name=View1 w=512 h=512
 vglinfo
 
-vvbo 0
-vsetdispmode 1
-vcamera -persp
-
-box b 1 1 1 
-explode b FACE 
-vdisplay b_1 b_2 b_3 b_5 b_6
-
-vfront
-vfit
-
-vsetmaterial b_1 plastic
-vsetmaterial b_2 plastic
-vsetmaterial b_3 plastic
-vsetmaterial b_5 plastic
-vsetmaterial b_6 plastic
-
-vbsdf b_1 -kd 1 -ks 0
-vbsdf b_2 -kd 1 -ks 0
-vbsdf b_3 -kd 1 -ks 0
-vbsdf b_5 -kd 1 -ks 0
-vbsdf b_6 -kd 1 -ks 0
-
-vbsdf b_2 -kd 0.3 0.5 1
-vbsdf b_1 -kd 1 0.3 0.3
-
-vsetlocation b_1  1  0  0
-vsetlocation b_2 -1  0  0
-vsetlocation b_5  0  0  1
-vsetlocation b_6  0  0 -1
-vsetlocation b_3  0  1  0
-
+# setup light sources
 vlight del 0
 vlight del 1
 vlight add positional head 0 pos 0.5 0.5 0.85
 vlight change 0 sm 0.06
 vlight change 0 int 60.0
 
+vvbo 0
+vsetdispmode 1
+vcamera -persp
+
+# setup outer box
+box b 1 1 1 
+explode b FACE 
+vdisplay b_1 b_2 b_3 b_5 b_6
+vsetlocation b_1  1  0  0
+vsetlocation b_2 -1  0  0
+vsetlocation b_3  0  1  0
+vsetlocation b_5  0  0  1
+vsetlocation b_6  0  0 -1
+
+vsetmaterial b_1 plastic
+vsetmaterial b_2 plastic
+vsetmaterial b_3 plastic
+vsetmaterial b_5 plastic
+vsetmaterial b_6 plastic
+vbsdf b_1 -kd 1 0.3 0.3 -ks 0
+vbsdf b_2 -kd 0.3 0.5 1 -ks 0
+vbsdf b_3 -kd 1 -ks 0
+vbsdf b_5 -kd 1 -ks 0
+vbsdf b_6 -kd 1 -ks 0
+
+vfront
+vfit
+
+# setup first inner sphere
 psphere s 0.2
 vdisplay s
 vsetlocation s 0.21 0.3 0.2
@@ -53,6 +53,7 @@ vsetmaterial s glass
 vbsdf s -absorpcolor 0.8 0.8 1.0
 vbsdf s -absorpcoeff 6
 
+# setup first inner box
 box c 0.3 0.3 0.2
 vdisplay c
 vsetlocation c 0.55 0.3 0.0
@@ -60,6 +61,7 @@ vlocrotate c 0 0 0 0 0 1 -30
 vsetmaterial c plastic
 vbsdf c -kd 1.0 0.8 0.2 -ks 0.3 -n
 
+# setup second inner box
 box g 0.15 0.15 0.3
 vdisplay g
 vsetlocation g 0.7 0.25 0.2
@@ -68,6 +70,7 @@ vsetmaterial g glass
 vbsdf g -absorpcolor 0.8 1.0 0.8
 vbsdf g -absorpcoeff 6
 
+# setup second inner sphere
 psphere r 0.1
 vdisplay r
 vsetmaterial r plastic
@@ -75,4 +78,10 @@ vbsdf r -kd 0.5 0.9 0.3 -ks 0.0 -kr 0.3 -n
 vbsdf r -fresnel Constant 1.0
 vsetlocation r 0.5 0.65 0.1
 
+puts "Trying path tracing mode..."
 vrenderparams -ray -gi -rayDepth 8
+
+puts "Make several path tracing iterations to refine the picture, please wait..."
+vfps 100
+puts "Done. To improve the image further, or after view manipulations, give command:"
+puts "vfps \[nb_iteratons\]"