Do some hollowing finally.

tests/hollowing/openvdb_utils.hpp

@@ -0,0 +1,25 @@
+#ifndef OPENVDB_UTILS_HPP
+#define OPENVDB_UTILS_HPP
+
+#include <libslic3r/TriangleMesh.hpp>
+#include <libslic3r/SLA/SLABoilerPlate.hpp>
+#include <openvdb/openvdb.h>
+#include <openvdb/tools/MeshToVolume.h>
+#include <openvdb/tools/VolumeToMesh.h>
+
+namespace Slic3r {
+
+openvdb::FloatGrid::Ptr meshToVolume(const TriangleMesh &            mesh,
+                                     const openvdb::math::Transform &tr);
+
+openvdb::FloatGrid::Ptr meshToVolume(const sla::Contour3D &          mesh,
+                                     const openvdb::math::Transform &tr);
+
+sla::Contour3D volumeToMesh(const openvdb::FloatGrid &grid,
+                            double                    isovalue   = 0.0,
+                            double                    adaptivity = 0.0,
+                            bool relaxDisorientedTriangles       = true);
+
+} // namespace Slic3r
+
+#endif // OPENVDB_UTILS_HPP