From 145f0489b877c17443ca4a9cd82e05d28e987fe3 Mon Sep 17 00:00:00 2001
From: enricoturri1966 <enricoturri@seznam.cz>
Date: Wed, 27 Oct 2021 08:56:10 +0200
Subject: [PATCH] Fixed crash when a part of a multipart object is completely
 below the printbed

---
 src/libslic3r/Model.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/libslic3r/Model.cpp b/src/libslic3r/Model.cpp
index 2dcf342116..8531ab07e0 100644
--- a/src/libslic3r/Model.cpp
+++ b/src/libslic3r/Model.cpp
@@ -1587,6 +1587,10 @@ unsigned int ModelObject::check_instances_print_volume_state(const Polygon& prin
             if (vol->is_model_part()) {
                 const Transform3d matrix = model_instance->get_matrix() * vol->get_matrix();
                 const BoundingBoxf3 bb = vol->mesh().transformed_bounding_box(matrix, 0.0);
+                if (!bb.defined) {
+                    // this may happen if the part is fully below the printbed, leading to a crash in the following call to its_convex_hull_2d_above()
+                    continue;
+                }
                 const Polygon volume_hull_2d = its_convex_hull_2d_above(vol->mesh().its, matrix.cast<float>(), 0.0f);
                 ModelInstanceEPrintVolumeState state = printbed_collision_state(printbed_shape, print_volume_height, volume_hull_2d, bb.min.z(), bb.max.z());
                 if (state == ModelInstancePVS_Inside)