=== modified file 'src/display/nr-filter-turbulence.cpp'
--- src/display/nr-filter-turbulence.cpp	2014-03-27 01:33:44 +0000
+++ src/display/nr-filter-turbulence.cpp	2015-01-03 07:12:26 +0000
@@ -66,6 +66,10 @@
 
                 _gradient[i][k][0] = static_cast<double>(_random() % (BSize*2) - BSize) / BSize;
                 _gradient[i][k][1] = static_cast<double>(_random() % (BSize*2) - BSize) / BSize;
+                if (_gradient[i][k][0] == 0 && _gradient[i][k][1] == 0) {
+                        _gradient[i][k][0] = 1;
+                        _gradient[i][k][1] = 1;
+                }
 
                 // normalize gradient
                 double s = hypot(_gradient[i][k][0], _gradient[i][k][1]);