From 1bd2fee41401eee1edbd8c739fc353ccb80e1ae0 Mon Sep 17 00:00:00 2001
From: kgv <kgv@opencascade.com>
Date: Tue, 25 Aug 2015 15:43:31 +0300
Subject: [PATCH] 0026601: Visualization, Ray Tracing - make Path Tracing
 results reproducible for the same camera position

OpenGl_View - reset Random Number Generator seed on progressive render restart
to produce the same visual results.
---
 src/OpenGl/OpenGl_View_Raytrace.cxx |  5 +++++
 src/math/math_BullardGenerator.hxx  | 15 +++++++++++----
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/src/OpenGl/OpenGl_View_Raytrace.cxx b/src/OpenGl/OpenGl_View_Raytrace.cxx
index f7bd08ba15..27c76a7878 100644
--- a/src/OpenGl/OpenGl_View_Raytrace.cxx
+++ b/src/OpenGl/OpenGl_View_Raytrace.cxx
@@ -2396,6 +2396,11 @@ Standard_Boolean OpenGl_View::runRaytraceShaders (const Graphic3d_CView&
 
   if (myRaytraceParameters.GlobalIllumination)
   {
+    if (myAccumFrames == 0)
+    {
+      myRNG.SetSeed();
+    }
+
     // Set frame accumulation weight
     myRaytraceProgram->SetUniform (theGlContext,
       myUniformLocations[0][OpenGl_RT_uSampleWeight], 1.f / (myAccumFrames + 1));
diff --git a/src/math/math_BullardGenerator.hxx b/src/math/math_BullardGenerator.hxx
index ff604ec720..4b682d2440 100644
--- a/src/math/math_BullardGenerator.hxx
+++ b/src/math/math_BullardGenerator.hxx
@@ -24,14 +24,21 @@ class math_BullardGenerator
 public:
 
   //! Creates new Xorshift 64-bit RNG.
-  Standard_EXPORT math_BullardGenerator(unsigned int theSeed = 1)
-    : myStateHi (theSeed)
+  math_BullardGenerator (unsigned int theSeed = 1)
+  : myStateHi (theSeed)
   {
+    SetSeed (theSeed);
+  }
+
+  //! Setup new seed / reset defaults.
+  void SetSeed (unsigned int theSeed = 1)
+  {
+    myStateHi = theSeed;
     myStateLo = theSeed ^ 0x49616E42;
   }
 
   //! Generates new 64-bit integer value.
-  Standard_EXPORT unsigned int NextInt()
+  unsigned int NextInt()
   {
     myStateHi = (myStateHi >> 2) + (myStateHi << 2);
 
@@ -42,7 +49,7 @@ public:
   }
 
   //! Generates new floating-point value.
-  Standard_EXPORT Standard_Real NextReal()
+  Standard_Real NextReal()
   {
     return NextInt() / static_cast<Standard_Real> (0xFFFFFFFFu);
   }