diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1360792..5ec059b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2,7 +2,7 @@ cmake_minimum_required(VERSION 3.18)
 
 project(hyperboloid VERSION 1.0.0 LANGUAGES CXX)
 
-set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 if(POLICY CMP0175)
diff --git a/Cargo.lock b/Cargo.lock
index 07cf9ee..96a81a8 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -640,6 +640,7 @@ version = "0.1.0"
 dependencies = [
  "glam",
  "hyperboloid",
+ "libc",
  "pollster",
  "raw-window-handle",
  "wgpu",
@@ -716,9 +717,9 @@ checksum = "e2db585e1d738fc771bf08a151420d3ed193d9d895a36df7f6f8a9456b911ddc"
 
 [[package]]
 name = "libc"
-version = "0.2.180"
+version = "0.2.186"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bcc35a38544a891a5f7c865aca548a982ccb3b8650a5b06d0fd33a10283c56fc"
+checksum = "68ab91017fe16c622486840e4c83c9a37afeff978bd239b5293d61ece587de66"
 
 [[package]]
 name = "libloading"
diff --git a/src/lib.rs b/src/lib.rs
index 389581e..e20fd95 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -229,6 +229,19 @@ impl Core {
 	}
 }
 
+pub fn write_obj(mut target: impl std::io::Write, args: &ShapeArgs) -> std::io::Result<()> {
+	let mesh = mesh::make(args);
+	writeln!(target, "o Hyperboloid")?;
+	for v in mesh.vertices {
+		writeln!(target, "v {} {} {}", v.x, v.y, v.z)?;
+	}
+	for f in mesh.faces {
+		writeln!(target, "f {} {} {}", f[0] + 1, f[1] + 1, f[2] + 1)?;
+	}
+	target.flush()?;
+	Ok(())
+}
+
 pub async fn init_gpu_inner<E: Error + 'static>(
 	make_surface: impl FnOnce(&wgpu::Instance) -> Result<wgpu::Surface<'static>, E>,
 ) -> Result<Gpu, Box<dyn Error>> {
diff --git a/ui/Cargo.toml b/ui/Cargo.toml
index 6cdd6b2..4cd5bd0 100644
--- a/ui/Cargo.toml
+++ b/ui/Cargo.toml
@@ -13,3 +13,4 @@ glam = { version = "0.30" }
 pollster = "0.4.0"
 raw-window-handle = "0.6.2"
 wgpu = "27.0.1"
+libc = "0.2.186"
diff --git a/ui/src/api.cxx b/ui/src/api.cxx
index aaa2b64..7114667 100644
--- a/ui/src/api.cxx
+++ b/ui/src/api.cxx
@@ -1,13 +1,17 @@
 #include "api.hxx"
 
+#include <memory>
 #include <stdexcept>
 #include <utility>
 
+#include <QByteArray>
+
 namespace ffi {
 extern "C" Core* rt4_viewport_create(xcb_connection_t* connection, std::uint32_t window, std::uint32_t width, std::uint32_t height);
 extern "C" void rt4_viewport_destroy(Core* viewport);
 extern "C" void rt4_viewport_configure(Core* viewport, std::uint32_t width, std::uint32_t height);
 extern "C" void rt4_viewport_redraw(Core* viewport, const RedrawArgs* args);
+extern "C" ByteArray rt4_make_obj(const ShapeArgs* args);
 } // namespace ffi
 
 BoxCore::BoxCore(BoxCore&& b)
@@ -55,3 +59,11 @@ void MutCore::configure(std::uint32_t width, std::uint32_t height) const {
 void MutCore::redraw(const RedrawArgs& args) const {
 	rt4_viewport_redraw(use(), &args);
 }
+
+using free_deleter = decltype([](void* ptr) { free(ptr); });
+
+QByteArray make_obj(const ShapeArgs& args) {
+	ffi::ByteArray arr = rt4_make_obj(&args);
+	std::unique_ptr<void, free_deleter> ptr(arr.data);
+	return QByteArray(reinterpret_cast<const char*>(arr.data), arr.length);
+}
diff --git a/ui/src/api.hxx b/ui/src/api.hxx
index 1a1162c..a0f62ea 100644
--- a/ui/src/api.hxx
+++ b/ui/src/api.hxx
@@ -1,9 +1,12 @@
 #pragma once
 
+#include <cstddef>
 #include <cstdint>
 
 struct xcb_connection_t;
 
+class QByteArray;
+
 struct alignas(16) Vec4 {
 	float x, y, z, w;
 };
@@ -11,6 +14,11 @@ struct alignas(16) Vec4 {
 namespace ffi {
 struct Core;
 
+struct ByteArray {
+	std::byte* data;
+	std::size_t length;
+};
+
 enum class Mode: std::uint32_t {
 	Solid,
 	Shell,
@@ -82,3 +90,5 @@ public:
 private:
 	MutCore ptr;
 };
+
+QByteArray make_obj(const ShapeArgs& args);
diff --git a/ui/src/lib.rs b/ui/src/lib.rs
index 251f3a7..2fb43dc 100644
--- a/ui/src/lib.rs
+++ b/ui/src/lib.rs
@@ -1,9 +1,15 @@
 use std::{ffi::c_void, num::NonZero, ptr::NonNull};
 
-use hyperboloid::{Core, RedrawArgs, init_gpu_inner};
 use glam::{UVec2, uvec2};
+use hyperboloid::{Core, RedrawArgs, ShapeArgs, init_gpu_inner, write_obj};
 use raw_window_handle::{RawDisplayHandle, RawWindowHandle, XcbDisplayHandle, XcbWindowHandle};
 
+#[repr(C)]
+pub struct ByteArray {
+	data: *mut u8,
+	length: usize,
+}
+
 unsafe fn create_viewport(
 	display: impl Into<RawDisplayHandle>,
 	window: impl Into<RawWindowHandle>,
@@ -46,3 +52,16 @@ unsafe extern "C" fn rt4_viewport_configure(viewport: &mut Core, width: u32, hei
 unsafe extern "C" fn rt4_viewport_redraw(viewport: &mut Core, args: &RedrawArgs) {
 	viewport.redraw(args);
 }
+
+#[unsafe(no_mangle)]
+unsafe extern "C" fn rt4_make_obj(args: &ShapeArgs) -> ByteArray {
+	let mut buf = Vec::new();
+	write_obj(&mut buf, args).expect("writing to a Vec is infallible");
+	let data = unsafe { libc::malloc(buf.len()) };
+	assert!(!data.is_null());
+	unsafe { libc::memcpy(data, buf.as_ptr() as *const c_void, buf.len()) };
+	ByteArray {
+		data: data as *mut u8,
+		length: buf.len(),
+	}
+}
diff --git a/ui/src/main_window.cxx b/ui/src/main_window.cxx
index 2325c55..b951acc 100644
--- a/ui/src/main_window.cxx
+++ b/ui/src/main_window.cxx
@@ -1,11 +1,14 @@
 #include "main_window.hxx"
 
+#include <QFileDialog>
+
 #include "ui_main_window.h"
 
 Hyperboloid::Hyperboloid(QWidget* parent)
 	: QMainWindow(parent),
 	  m_ui(new Ui::MainWindow) {
 	m_ui->setupUi(this);
+	m_ui->btnExport->setDefaultAction(m_ui->actionExport);
 	m_ui->mode->setId(m_ui->modeSolid, (int)Mode::Solid);
 	m_ui->mode->setId(m_ui->modeShell, (int)Mode::Shell);
 	m_ui->mode->setId(m_ui->modeMesh, (int)Mode::Mesh);
@@ -31,12 +34,8 @@ void Hyperboloid::updateModeUi() {
 	m_ui->lineWidth->setEnabled(has_line_width);
 }
 
-void Hyperboloid::updateView() {
-	const int max_layers = (m_ui->sides->value() - 1) / 2;
-	m_ui->layersUp->setMaximum(max_layers);
-	m_ui->layersDown->setMaximum(max_layers);
-	const auto color = m_ui->inBackground->color();
-	const ShapeArgs shape {
+ffi::ShapeArgs Hyperboloid::makeShapeArgs() const {
+	return {
 		.mode = modeFromInt(m_ui->mode->checkedId()),
 		.sides = (std::uint32_t)m_ui->sides->value(),
 		.layers_up = (std::uint32_t)m_ui->layersUp->value(),
@@ -46,8 +45,15 @@ void Hyperboloid::updateView() {
 		.thickness = (float)m_ui->thickness->value(),
 		.line_width = (float)m_ui->lineWidth->value(),
 	};
+}
+
+void Hyperboloid::updateView() {
+	const int max_layers = (m_ui->sides->value() - 1) / 2;
+	m_ui->layersUp->setMaximum(max_layers);
+	m_ui->layersDown->setMaximum(max_layers);
+	const auto color = m_ui->inBackground->color();
 	const RedrawArgs args{
-		.shape = shape,
+		.shape = makeShapeArgs(),
 		.background = { color.redF(), color.greenF(), color.blueF(), 1.00 },
 		.camera_yaw = qDegreesToRadians((float)m_ui->camYaw->value()),
 		.camera_pitch = qDegreesToRadians((float)m_ui->camPitch->value()),
@@ -57,4 +63,10 @@ void Hyperboloid::updateView() {
 	m_ui->viewport->setView(args);
 }
 
+void Hyperboloid::on_actionExport_triggered() {
+	const auto shape = makeShapeArgs();
+	const auto obj = make_obj(shape);
+	QFileDialog::saveFileContent(obj, "hyperboloid.obj", this);
+}
+
 #include "moc_main_window.cpp"
diff --git a/ui/src/main_window.hxx b/ui/src/main_window.hxx
index 342f9c4..3e18a9e 100644
--- a/ui/src/main_window.hxx
+++ b/ui/src/main_window.hxx
@@ -7,6 +7,10 @@ namespace Ui {
 class MainWindow;
 }
 
+namespace ffi {
+struct ShapeArgs;
+}
+
 class Hyperboloid : public QMainWindow {
 	Q_OBJECT
 
@@ -17,7 +21,10 @@ public:
 public slots:
 	void updateModeUi();
 	void updateView();
+	void on_actionExport_triggered();
 
 private:
 	const std::unique_ptr<Ui::MainWindow> m_ui;
+
+	ffi::ShapeArgs makeShapeArgs() const;
 };
diff --git a/ui/src/main_window.ui b/ui/src/main_window.ui
index ddac555..a9b65b6 100644
--- a/ui/src/main_window.ui
+++ b/ui/src/main_window.ui
@@ -375,6 +375,22 @@
        </layout>
       </widget>
      </item>
+     <item>
+      <widget class="QToolButton" name="btnExport">
+       <property name="sizePolicy">
+        <sizepolicy hsizetype="Preferred" vsizetype="Fixed">
+         <horstretch>0</horstretch>
+         <verstretch>0</verstretch>
+        </sizepolicy>
+       </property>
+       <property name="text">
+        <string>&amp;Export...</string>
+       </property>
+       <property name="toolButtonStyle">
+        <enum>Qt::ToolButtonStyle::ToolButtonTextBesideIcon</enum>
+       </property>
+      </widget>
+     </item>
      <item>
       <spacer name="verticalSpacer">
        <property name="orientation">
@@ -391,6 +407,20 @@
     </layout>
    </widget>
   </widget>
+  <action name="actionExport">
+   <property name="icon">
+    <iconset theme="QIcon::ThemeIcon::DocumentSaveAs"/>
+   </property>
+   <property name="text">
+    <string>&amp;Export...</string>
+   </property>
+   <property name="shortcut">
+    <string>Ctrl+E</string>
+   </property>
+   <property name="menuRole">
+    <enum>QAction::MenuRole::NoRole</enum>
+   </property>
+  </action>
  </widget>
  <customwidgets>
   <customwidget>