diff --git a/CMakeLists.txt b/CMakeLists.txt
index 602550b74..b13acece1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,10 @@
 # main project file. use it from a build sub-folder, see COMPILE for details
 
+## setting the build type.
+IF(NOT DEFINED CMAKE_BUILD_TYPE OR CMAKE_BUILD_TYPE STREQUAL "")
+  SET(CMAKE_BUILD_TYPE "Release" CACHE STRING "Choose the type of build, options are: Release RelWithDebInfo.")
+ENDIF()
+
 ## some generic CMake magic
 cmake_minimum_required(VERSION 2.8 FATAL_ERROR)
 project(dfhack)
@@ -14,11 +19,6 @@ if("${CMAKE_SOURCE_DIR}" STREQUAL "${CMAKE_BINARY_DIR}")
    message(FATAL_ERROR "In-source builds are not allowed.")
 endif()
 
-## setting the build type.
-IF(NOT DEFINED CMAKE_BUILD_TYPE OR CMAKE_BUILD_TYPE STREQUAL "")
-  SET(CMAKE_BUILD_TYPE "Release" CACHE STRING "Choose the type of build, options are: Release RelWithDebInfo.")
-ENDIF()
-
 # set up versioning.
 set(DF_VERSION_MAJOR "0")
 set(DF_VERSION_MINOR "31")
diff --git a/plugins/vdig.cpp b/plugins/vdig.cpp
index 65e763478..f8b2ea3fb 100644
--- a/plugins/vdig.cpp
+++ b/plugins/vdig.cpp
@@ -9,7 +9,7 @@
 #include <cstdio>
 #include <stack>
 #include <string>
-
+#include <cmath>
 using std::vector;
 using std::string;
 using std::stack;
@@ -63,8 +63,8 @@ DFhackCExport command_result digcircle (Core * c, vector <string> & parameters)
     static bool filled = false;
     static circle_what what = circle_set;
     static e_designation type = designation_default;
-    static int r = 0;
-    auto saved_r = r;
+    static int diameter = 0;
+    auto saved_d = diameter;
     bool force_help = false;
     for(int i = 0; i < parameters.size();i++)
     {
@@ -112,14 +112,14 @@ DFhackCExport command_result digcircle (Core * c, vector <string> & parameters)
         {
             type = designation_channel;
         }
-        else if (!from_string(r,parameters[i], std::dec))
+        else if (!from_string(diameter,parameters[i], std::dec))
         {
-            r = saved_r;
+            diameter = saved_d;
         }
     }
-    if(r < 0)
-        r = -r;
-    if(force_help || r == 0)
+    if(diameter < 0)
+        diameter = -diameter;
+    if(force_help || diameter == 0)
     {
         c->con.print(   "A command for easy designation of filled and hollow circles.\n"
                         "\n"
@@ -137,7 +137,7 @@ DFhackCExport command_result digcircle (Core * c, vector <string> & parameters)
                         " xstair = staircase up/down\n"
                         "   chan = dig channel\n"
                         "\n"
-                        "      # = radius in tiles (default = 0)\n"
+                        "      # = diameter in tiles (default = 0)\n"
                         "\n"
                         "After you have set the options, the command called with no options\n"
                         "repeats with the last selected parameters:\n"
@@ -173,10 +173,16 @@ DFhackCExport command_result digcircle (Core * c, vector <string> & parameters)
         auto b = MCache.BlockAt(at/16);
         if(!b || !b->valid)
             return false;
-        if(x == 0 || x == x_max - 1)
+        if(x == 0 || x == x_max * 16 - 1)
+        {
+            //c->con.print("not digging map border\n");
             return false;
-        if(y == 0 || y == y_max - 1)
+        }
+        if(y == 0 || y == y_max * 16 - 1)
+        {
+            //c->con.print("not digging map border\n");
             return false;
+        }
         uint16_t tt = MCache.tiletypeAt(at);
         t_designation des = MCache.designationAt(at);
         // could be potentially used to locate hidden constructions?
@@ -242,53 +248,71 @@ DFhackCExport command_result digcircle (Core * c, vector <string> & parameters)
         }
         return true;
     };
-    int f = 1 - r;
-    int ddF_x = 1;
-    int ddF_y = -2 * r;
-    int x = 0;
-    int y = r;
-    if(!filled)
-    {
-        dig(cx, cy + r, cz);
-        dig(cx, cy - r, cz);
-        dig(cx + r, cy, cz);
-        dig(cx - r, cy, cz);
+    int r = diameter / 2;
+    int iter;
+    bool adjust;
+    if(diameter % 2)
+    {
+        // paint center
+        if(filled)
+        {
+            lineY(cx - r, cx + r, cy, cz);
+        }
+        else
+        {
+            dig(cx - r, cy, cz);
+            dig(cx + r, cy, cz);
+        }
+        adjust = false;
+        iter = 2;
     }
     else
     {
-        lineX(cy-r, cy+r, cx, cz);
-        lineY(cx-r, cx+r, cy, cz);
+        adjust = true;
+        iter = 1;
     }
-
-    while(x < y)
-    {
-        if(f >= 0)
-        {
-            y--;
-            ddF_y += 2;
-            f += ddF_y;
+    int lastwhole = r;
+    for(; iter <= diameter - 1; iter +=2)
+    {
+        // top, bottom coords
+        int top = cy - ((iter + 1) / 2) + adjust;
+        int bottom = cy + ((iter + 1) / 2);
+        // see where the current 'line' intersects the circle
+        double val = std::sqrt(diameter*diameter - iter*iter);
+        // adjust for circles with odd diameter
+        if(!adjust)
+            val -= 1;
+        // map the found value to the DF grid
+        double whole;
+        double fraction = std::modf(val / 2.0, & whole);
+        if (fraction > 0.5)
+            whole += 1.0;
+        int right = cx + whole;
+        int left = cx - whole + adjust;
+        int diff = lastwhole - whole;
+        // paint
+        if(filled || iter == diameter - 1)
+        {
+            lineY(left, right, top , cz);
+            lineY(left, right, bottom , cz);
         }
-        x++;
-        ddF_x += 2;
-        f += ddF_x;
-        if(!filled)
+        else
         {
-            dig(cx + x, cy + y, cz);
-            dig(cx - x, cy + y, cz);
-            dig(cx + x, cy - y, cz);
-            dig(cx - x, cy - y, cz);
-            dig(cx + y, cy + x, cz);
-            dig(cx - y, cy + x, cz);
-            dig(cx + y, cy - x, cz);
-            dig(cx - y, cy - x, cz);
+            dig(left, top, cz);
+            dig(left, bottom, cz);
+            dig(right, top, cz);
+            dig(right, bottom, cz);
         }
-        else
+        if(!filled && diff > 1)
         {
-            lineY(cx-x, cx+x, cy+y, cz);
-            lineY(cx-x, cx+x, cy-y, cz);
-            lineY(cx-y, cx+y, cy+x, cz);
-            lineY(cx-y, cx+y, cy-x, cz);
+            int lright = cx + lastwhole;
+            int lleft = cx - lastwhole + adjust;
+            lineY(lleft + 1, left - 1, top + 1 , cz);
+            lineY(right + 1, lright - 1, top + 1 , cz);
+            lineY(lleft + 1, left - 1, bottom - 1 , cz);
+            lineY(right + 1, lright - 1, bottom - 1 , cz);
         }
+        lastwhole = whole;
     }
     MCache.WriteAll();
     c->Resume();