diff --git a/common/Domain.cpp b/common/Domain.cpp
index 945a6c6a..14dc17dd 100644
--- a/common/Domain.cpp
+++ b/common/Domain.cpp
@@ -217,17 +217,23 @@ void Domain::read_swc(const std::string &Filename) {
 					double z = k*voxel_length + start_z;
 					
 					double distance; 
-					double s = ((x-xp)*alpha+(y-yp)*beta+(z-zp)*gamma) / (alpha*alpha + beta*beta + gamma*gamma);					
+					double s = ((x-xp)*alpha+(y-yp)*beta+(z-zp)*gamma) / (alpha*alpha + beta*beta + gamma*gamma);	
+					
+					double di = ri - sqrt((x-xi)*(x-xi) + (y-yi)*(y-yi) + (z-zi)*(z-zi));
+					double dp = rp - sqrt((x-xp)*(x-xp) + (y-yp)*(y-yp) + (z-zp)*(z-zp));
+
 					if (s > length){
-						distance = ri - sqrt((x-xi)*(x-xi) + (y-yi)*(y-yi) + (z-zi)*(z-zi));
+						distance = di;
 					}
 					else if (s < 0.0){
-						distance = rp - sqrt((x-xp)*(x-xp) + (y-yp)*(y-yp) + (z-zp)*(z-zp));
+						distance = dp;
 					}
 					else {
 						// linear variation for radius
 						double radius = rp + (ri - rp)*s/length;
 						distance = radius - sqrt((x-xp-alpha*s)*(x-xp-alpha*s) + (y-yp-beta*s)*(y-yp-beta*s) + (z-zp-gamma*s)*(z-zp-gamma*s));
+						if (distance < di) distance = di;
+						if (distance < dp) distance = dp;
 					}
 					if ( distance > 0.0 ){
 						/* label the voxel */