getState enforcePeriodicBox with triclinic unit cells

openmmapi/src/Context.cpp

@@ -114,21 +114,15 @@ State Context::getState(int types, bool enforcePeriodicBox, int groups) const {
                 center *= 1.0/molecules[i].size();
 
                 // Find the displacement to move it into the first periodic box.
-
-                int xcell = (int) floor(center[0]/periodicBoxSize[0][0]);
-                int ycell = (int) floor(center[1]/periodicBoxSize[1][1]);
-                int zcell = (int) floor(center[2]/periodicBoxSize[2][2]);
-                double dx = xcell*periodicBoxSize[0][0];
-                double dy = ycell*periodicBoxSize[1][1];
-                double dz = zcell*periodicBoxSize[2][2];
+                Vec3 diff;
+                diff -= periodicBoxSize[0]*static_cast<int>(center[0]/periodicBoxSize[0][0]);
+                diff -= periodicBoxSize[1]*static_cast<int>(center[1]/periodicBoxSize[1][1]);
+                diff -= periodicBoxSize[2]*static_cast<int>(center[2]/periodicBoxSize[2][2]);
 
                 // Translate all the particles in the molecule.
-                
                 for (int j = 0; j < (int) molecules[i].size(); j++) {
                     Vec3& pos = positions[molecules[i][j]];
-                    pos[0] -= dx;
-                    pos[1] -= dy;
-                    pos[2] -= dz;
+                    pos -= diff;
                 }
             }
         }