diff --git a/pattern2.cpp b/pattern2.cpp
index 48718bce..759ae49b 100644
--- a/pattern2.cpp
+++ b/pattern2.cpp
@@ -1661,9 +1661,10 @@ EX namespace patterns {
         }
       case 'f': {
         color_t res;
-        for(int i=0; i<3; i++) {
+        for(int i=0; i<4; i++) {
           ld v = real(compute_map_function(c, 1+i, color_formula));
-          if(v < 0) part(res, i) = 0;
+          if(i == 3) part(res, i) = (v > 0);
+          else if(v < 0) part(res, i) = 0;
           else if(v > 1) part(res, i) = 255;
           else part(res, i) = int(v * 255 + .5);
           }
diff --git a/util.cpp b/util.cpp
index bb1e5127..92938788 100644
--- a/util.cpp
+++ b/util.cpp
@@ -183,6 +183,13 @@ cld exp_parser::parse(int prio) {
     cld no = parsepar();
     return real(cond) > 0 ? yes : no;
     }  
+  else if(eat("wallif(")) {
+    cld val0 = parse(0);
+    if(next() != ',') {at = -1; return 0; } at++;
+    cld val1 = parsepar();
+    if(real(extra_params["p"]) >= 3.5) return val0;
+    else return val1;
+    }
   else if(eat("rgb(")) {     
     cld val0 = parse(0);
     if(next() != ',') {at = -1; return 0; } at++;