From 052efbf2c3c669861e946e2e89ac9f6bdd3bf606 Mon Sep 17 00:00:00 2001
From: remi durand <remi-j.durand@thalesgroup.com>
Date: Thu, 3 Jun 2021 19:01:00 +0200
Subject: [PATCH] fix error on extruders when no support interface
 supermerill/SuperSlicer#1233

---
 src/libslic3r/Print.cpp | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/src/libslic3r/Print.cpp b/src/libslic3r/Print.cpp
index 2fb2aaa51..5db104f47 100644
--- a/src/libslic3r/Print.cpp
+++ b/src/libslic3r/Print.cpp
@@ -375,15 +375,17 @@ std::vector<uint16_t> Print::support_material_extruders() const
                 uint16_t i = (uint16_t)object->config().support_material_extruder - 1;
                 extruders.emplace_back((i >= num_extruders) ? 0 : i);
             }
-        	assert(object->config().support_material_interface_extruder >= 0);
-            if (object->config().support_material_interface_extruder == 0)
-                support_uses_current_extruder = true;
-            else {
-                uint16_t i = (uint16_t)object->config().support_material_interface_extruder - 1;
-                extruders.emplace_back((i >= num_extruders) ? 0 : i);
+            if (object->config().support_material_interface_layers > 0) {
+                assert(object->config().support_material_interface_extruder >= 0);
+                if (object->config().support_material_interface_extruder == 0)
+                    support_uses_current_extruder = true;
+                else {
+                    uint16_t i = (uint16_t)object->config().support_material_interface_extruder - 1;
+                    extruders.emplace_back((i >= num_extruders) ? 0 : i);
+                }
+            }
         }
     }
-    }
 
     if (support_uses_current_extruder)
         // Add all object extruders to the support extruders as it is not know which one will be used to print supports.