diff --git a/base.scad b/base.scad
new file mode 100644
index 0000000..8a2df46
--- /dev/null
+++ b/base.scad
@@ -0,0 +1 @@
+function default(val,comp) = val != undef ? val : comp;
diff --git a/component.scad b/component.scad
index 89c8056..fe9e27c 100644
--- a/component.scad
+++ b/component.scad
@@ -1,4 +1,4 @@
-
+use <./debug.scad>;
 module component_get(name) {
   component_display(name) children();
 }
@@ -9,5 +9,8 @@ module component_display(name) {
 }
 
 module component(name) {
-  if($scaddy_component ==  undef || $scaddy_component == name) children();
+  if($scaddy_component ==  undef || $scaddy_component == name) {
+      debug() echo(str("Displaying component ",name));
+      children();
+  }
 }
diff --git a/debug.scad b/debug.scad
index dc8b22b..1704c83 100644
--- a/debug.scad
+++ b/debug.scad
@@ -6,7 +6,7 @@ module debug(force=false) {
 }
 
 module _debug_mesh() {
-  %color([255,0,0,0.4]) children();
+  %color([1,0,0,0.4]) children();
 }
 
 module debug_points(vector) {
diff --git a/functions.scad b/functions.scad
index 359f07d..d9ea150 100644
--- a/functions.scad
+++ b/functions.scad
@@ -2,5 +2,4 @@ function circle_y(x,r,cx=0,cy=0) = (2*cy + sqrt(8*cx*x-4*cx*cx-4*(x)*(x)+4*r*r))
 
 function curve_r(curve_h,curve_w)=(pow(curve_h,2)+pow(curve_w,2))/(2*abs(curve_w));
 
-function pow2(x)=x*x;
-function pow3(x)=x*x*x;
+function mix(base,target,ratio) = base*(1-ratio)+target*ratio;
diff --git a/polyhedron.scad b/polyhedron.scad
index 5e65732..d0984fb 100644
--- a/polyhedron.scad
+++ b/polyhedron.scad
@@ -26,6 +26,6 @@ module polyhedron_layers(layers) {
                       bottom_f,
                       top_f,
                       walls_f
-                  ));
+                  ),convexity = lc);
 
 }
diff --git a/preconditions.scad b/preconditions.scad
index 413b446..3f41ed2 100644
--- a/preconditions.scad
+++ b/preconditions.scad
@@ -1,14 +1,23 @@
-module precondition(test,error) {
+use <./base.scad>;
+
+ERROR_BEGIN="<font color='red'>";
+ERROR_END="</font>";
+
+module precondition(test,error,m=undef) {
     if(!test) {
-        echo(str("<font color='red'>",error,"<font>"));
+        echo(str(ERROR_BEGIN,default(m,parent_module(1)),": ",error,ERROR_END));
         assert(false);
     } else children();
 }
 
-module check_defined(val,error) {
+function precondition(test,value,error)=test ? value : echo(str(ERROR_BEGIN,error,ERROR_END)) assert(false);
+
+module check_defined(val,error,m=undef) {
   precondition(val != undef,error) children();
 }
 
-module check_parent(parent,statement,error) {
+function check_defined(value,error)=precondition(value != undef,error);
+
+module check_parent(parent,statement,error,m=undef) {
     precondition(parent_module(3) == parent,str(statement,"(): ",error)) children();
 }
diff --git a/scaddy.scad b/scaddy.scad
index 74be9a0..c1b3f38 100644
--- a/scaddy.scad
+++ b/scaddy.scad
@@ -1,3 +1,4 @@
+include <./base.scad>;
 include <./debug.scad>;
 include <./config.scad>;
 include <./preconditions.scad>;