Opencl uses M_PI, which is defined <math.h> with _USE_MATH_DEFINES defined.

larshg · larshg · commit 1f23ff9f26e5 · 2014-12-19T16:45:58.000+01:00
diff --git a/examples/protonect/src/opencl_depth_packet_processor.cpp b/examples/protonect/src/opencl_depth_packet_processor.cpp
@@ -33,6 +33,11 @@
 #include <fstream>
 #include <sstream>
 
+#if defined(WIN32)
+#define _USE_MATH_DEFINES
+#include <math.h>
+#endif
+
 #define __CL_ENABLE_EXCEPTIONS
 #ifdef __APPLE__
   #include <OpenCL/cl.hpp>
