Added gallery.

sampling.cpp

@@ -1,5 +1,4 @@
-#ifdef _USE_CPP11_RANDOM
-#warning "Using C++11 random number generators."
+#ifdef USE_CPP11_RANDOM
 #include <random>
 #include <chrono>
 #include <functional>
@@ -13,7 +12,7 @@
 
 #include "sampling.hpp"
 
-#ifdef _USE_CPP11_RANDOM
+#ifdef USE_CPP11_RANDOM
 using std::uniform_real_distribution;
 using std::mt19937;
 using std::bind;
@@ -29,7 +28,7 @@ const float PDF = (1.0f / (2.0f * pi<float>()));
 
 static bool seeded = false;
 
-#ifdef _USE_CPP11_RANDOM
+#ifdef USE_CPP11_RANDOM
 static uniform_real_distribution<float> dist(0, 1);
 static mt19937 engine;
 static auto generator = bind(dist, engine);
@@ -37,14 +36,14 @@ static auto generator = bind(dist, engine);
 
 float random01() {
   if (!seeded) {
-#ifdef _USE_CPP11_RANDOM
+#ifdef USE_CPP11_RANDOM
     engine.seed(std::chrono::system_clock::now().time_since_epoch().count());
 #else
     srand(time(NULL));
 #endif
     seeded = true;
   }
-#ifdef _USE_CPP11_RANDOM
+#ifdef USE_CPP11_RANDOM
   return generator();
 #else
   return static_cast<float>(rand()) / RAND_MAX;