diff --git a/src/csg/csg.hpp b/src/csg/csg.hpp
index 1862b8305afc484ea004a513157274cc937b4454..7bce19472eeb6c2faef5594eb568050873080b8a 100644
--- a/src/csg/csg.hpp
+++ b/src/csg/csg.hpp
@@ -47,6 +47,8 @@ private:
   std::unique_ptr<Impl> m_pimpl;
 };
 
+std::unique_ptr<CsgIF> get_csgif_from_filename(std::string geom_file);
+
 } // namespace csg
 
 #endif
diff --git a/src/csg/impl/csg.cpp b/src/csg/impl/csg.cpp
index 1cb62eee5132ad1b2969f1f48d659fbb122fb937..7ea6c38ee30693a6c0321b2bea4b36fda775f0eb 100644
--- a/src/csg/impl/csg.cpp
+++ b/src/csg/impl/csg.cpp
@@ -1,7 +1,36 @@
+#include <fstream>
+#include <iostream>
+#include <sstream>
+
 #include "../csg.hpp"
 
 #include "csg_types.hpp"
 
+namespace {
+
+const std::string csg_ext = ".csg";
+
+bool has_ext(std::string filename, std::string extension) {
+  return filename.rfind(extension) == (filename.size() - extension.size());
+}
+
+std::optional<std::string> read_csg(std::string geom_file) {
+  if (!has_ext(geom_file, csg_ext)) {
+    std::cout << "Filename:  " << geom_file << "  must has extension .csg"
+              << std::endl;
+    return std::nullopt;
+  }
+
+  std::ifstream in_stream;
+  in_stream.open(geom_file.c_str());
+
+  std::stringstream str_stream;
+  str_stream << in_stream.rdbuf();
+  return str_stream.str();
+}
+
+} // namespace
+
 namespace csg {
 
 class CsgIF::Impl {
@@ -25,4 +54,22 @@ double CsgIF::operator()(double xx, double yy, double zz) const noexcept {
   return m_pimpl->call_signed_distance(m_state, xx, yy, zz);
 }
 
+std::unique_ptr<CsgIF> get_csgif_from_filename(std::string geom_file) {
+
+  auto csg_str = read_csg(geom_file);
+  if (!csg_str) {
+    std::cout << "Unable to read .csg file:  " << geom_file << std::endl;
+    return nullptr;
+  }
+  auto csg_obj = csg::parse_csg(csg_str.value());
+
+  if (!csg_obj) {
+    std::cout << "Failed to parse .csg file:  " << geom_file << std::endl;
+    return nullptr;
+  }
+
+  csg::CsgIF csg_if(csg_obj);
+  return std::make_unique<CsgIF>(csg_if);
+}
+
 } // namespace csg