diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8224de93..a292e3df 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -102,16 +102,16 @@ add_subdirectory(common)
 add_subdirectory(bspinfo)
 add_subdirectory(bsputil)
 add_subdirectory(light)
-
-if (ENABLE_LIGHTPREVIEW)
-	add_subdirectory(lightpreview)
-endif ()
-
 add_subdirectory(qbsp)
 add_subdirectory(vis)
 
 option(DISABLE_TESTS "Disables Tests" OFF)
 option(DISABLE_DOCS "Disables Docs" OFF)
+option(ENABLE_LIGHTPREVIEW "Enable light preview tool" OFF)
+
+if (ENABLE_LIGHTPREVIEW)
+	add_subdirectory(lightpreview)
+endif ()
 
 if(NOT DISABLE_TESTS)
 	# just creates testmaps.hh with absolute path to the testmaps source directory.
diff --git a/lightpreview/CMakeLists.txt b/lightpreview/CMakeLists.txt
index 1cb7df55..356327b7 100644
--- a/lightpreview/CMakeLists.txt
+++ b/lightpreview/CMakeLists.txt
@@ -2,7 +2,6 @@ project (lightpreview CXX)
 
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
 set(CMAKE_AUTOMOC ON)
-set(CMAKE_AUTOUIC ON)
 
 find_package(Qt5Widgets)
 
@@ -11,10 +10,29 @@ add_executable(lightpreview
     mainwindow.cpp
     mainwindow.h
     glview.cpp
-    glview.h
-    ${QBSP_SOURCES})
+    glview.h)
 
-target_link_libraries(lightpreview Qt5::Widgets)
+find_package(embree 3.0 REQUIRED)
+INCLUDE_DIRECTORIES(${EMBREE_INCLUDE_DIRS})
+
+# HACK: Windows embree .dll's from https://github.com/embree/embree/releases ship with a tbb12.dll
+# and we need to copy it from the embree/bin directory to our light.exe/testlight.exe dir in order for them to run
+find_file(EMBREE_TBB_DLL tbb12.dll
+        "${EMBREE_ROOT_DIR}/bin"
+        NO_DEFAULT_PATH)
+if (NOT EMBREE_TBB_DLL STREQUAL EMBREE_TBB_DLL-NOTFOUND)
+    message(STATUS "Found embree EMBREE_TBB_DLL: ${EMBREE_TBB_DLL}")
+endif()
+
+target_link_libraries(lightpreview
+        Qt5::Widgets
+        libqbsp
+        liblight
+        libvis
+        common
+        TBB::tbb
+        TBB::tbbmalloc
+        fmt::fmt)
 
 # from: http://stackoverflow.com/questions/40564443/copying-qt-dlls-to-executable-directory-on-windows-using-cmake
 # Copy Qt DLL's to bin directory for debugging
@@ -25,6 +43,17 @@ add_custom_command(
     COMMAND ${CMAKE_COMMAND} -E copy_if_different $<TARGET_FILE:Qt5::Core> $<TARGET_FILE_DIR:lightpreview>
 )
 
+# HACK: copy .dll dependencies
+add_custom_command(TARGET lightpreview POST_BUILD
+        COMMAND ${CMAKE_COMMAND} -E copy_if_different "$<TARGET_FILE:embree>"   "$<TARGET_FILE_DIR:lightpreview>"
+        COMMAND ${CMAKE_COMMAND} -E copy_if_different "$<TARGET_FILE:TBB::tbb>" "$<TARGET_FILE_DIR:lightpreview>"
+        COMMAND ${CMAKE_COMMAND} -E copy_if_different "$<TARGET_FILE:TBB::tbbmalloc>" "$<TARGET_FILE_DIR:lightpreview>"
+        )
+if (NOT EMBREE_TBB_DLL STREQUAL EMBREE_TBB_DLL-NOTFOUND)
+    add_custom_command(TARGET lightpreview POST_BUILD
+            COMMAND ${CMAKE_COMMAND} -E copy_if_different "${EMBREE_TBB_DLL}" "$<TARGET_FILE_DIR:lightpreview>")
+endif()
+
 # Install Qt DLL's
 install(FILES $<TARGET_FILE:Qt5::Widgets> DESTINATION bin)
 install(FILES $<TARGET_FILE:Qt5::Gui> DESTINATION bin)
diff --git a/lightpreview/glview.cpp b/lightpreview/glview.cpp
index 0075a312..f5659ff1 100644
--- a/lightpreview/glview.cpp
+++ b/lightpreview/glview.cpp
@@ -28,6 +28,8 @@ See file, 'COPYING', for details.
 #include <QTime>
 #include <fmt/core.h>
 
+#include <common/bspfile.hh>
+
 GLView::GLView(QWidget *parent)
     : QOpenGLWidget(parent),
       m_keysPressed(0),
@@ -236,3 +238,5 @@ void GLView::timerEvent(QTimerEvent *event)
 
     update(); // schedule a repaint
 }
+
+void GLView::renderBSP(const mbsp_t &bsp) { }
\ No newline at end of file
diff --git a/lightpreview/glview.h b/lightpreview/glview.h
index f4d7f60c..324440ff 100644
--- a/lightpreview/glview.h
+++ b/lightpreview/glview.h
@@ -38,6 +38,8 @@ enum class keys_t : uint32_t
     left = 8
 };
 
+struct mbsp_t;
+
 class GLView : public QOpenGLWidget, protected QOpenGLFunctions
 {
 private:
@@ -67,6 +69,8 @@ public:
     GLView(QWidget *parent = nullptr);
     ~GLView();
 
+    void renderBSP(const mbsp_t &bsp);
+
 protected:
     void initializeGL() override;
     void paintGL() override;
diff --git a/lightpreview/lightpreview.pro b/lightpreview/lightpreview.pro
deleted file mode 100644
index 9f8b0689..00000000
--- a/lightpreview/lightpreview.pro
+++ /dev/null
@@ -1,33 +0,0 @@
-#-------------------------------------------------
-#
-# Project created by QtCreator 2017-03-20T13:10:04
-#
-#-------------------------------------------------
-
-QT       += core gui
-
-greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
-
-TARGET = lightpreview
-TEMPLATE = app
-
-# The following define makes your compiler emit warnings if you use
-# any feature of Qt which as been marked as deprecated (the exact warnings
-# depend on your compiler). Please consult the documentation of the
-# deprecated API in order to know how to port your code away from it.
-DEFINES += QT_DEPRECATED_WARNINGS
-
-# You can also make your code fail to compile if you use deprecated APIs.
-# In order to do so, uncomment the following line.
-# You can also select to disable deprecated APIs only up to a certain version of Qt.
-#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0
-
-
-SOURCES += main.cpp\
-        mainwindow.cpp \
-    glview.cpp
-
-HEADERS  += mainwindow.h \
-    glview.h
-
-FORMS    += mainwindow.ui
diff --git a/lightpreview/mainwindow.cpp b/lightpreview/mainwindow.cpp
index 5797f063..3b745390 100644
--- a/lightpreview/mainwindow.cpp
+++ b/lightpreview/mainwindow.cpp
@@ -18,16 +18,130 @@ See file, 'COPYING', for details.
 */
 
 #include "mainwindow.h"
-#include "ui_mainwindow.h"
+
+#include <QDragEnterEvent>
+#include <QMimeData>
+#include <QFileSystemWatcher>
+
+#include <common/bspfile.hh>
+#include <qbsp/qbsp.hh>
+#include <vis/vis.hh>
+#include <light/light.hh>
+
+#include "glview.h"
 
 MainWindow::MainWindow(QWidget *parent)
-    : QMainWindow(parent),
-      ui(new Ui::MainWindow)
+    : QMainWindow(parent)
 {
-    ui->setupUi(this);
+    resize(640, 480);
+    glView = new GLView();
+    this->setCentralWidget(glView);
+
+    setAcceptDrops(true);
 }
 
-MainWindow::~MainWindow()
+MainWindow::~MainWindow() { }
+
+void MainWindow::dragEnterEvent(QDragEnterEvent *event)
 {
-    delete ui;
+    if (event->mimeData()->hasUrls())
+        event->acceptProposedAction();
 }
+
+void MainWindow::dropEvent(QDropEvent *event)
+{
+    auto urls = event->mimeData()->urls();
+    if (!urls.empty()) {
+        const QUrl &url = urls[0];
+        if (url.isLocalFile()) {
+            loadFile(url.toLocalFile());
+
+            event->acceptProposedAction();
+        }
+    }
+}
+
+void MainWindow::loadFile(const QString &file)
+{
+    qDebug() << "load " << file;
+
+    if (m_watcher) {
+        delete m_watcher;
+    }
+    m_watcher = new QFileSystemWatcher(this);
+
+    // start watching it
+    qDebug() << "adding path: " << m_watcher->addPath(file);
+    connect(m_watcher, &QFileSystemWatcher::fileChanged, this,
+        [](const QString &path) { qDebug() << "got change notif for " << path; });
+
+    loadFileInternal(file);
+}
+
+std::filesystem::path MakeFSPath(const QString &string)
+{
+    return std::filesystem::path{string.toStdU16String()};
+}
+
+static bspdata_t QbspVisLight_Common(const std::filesystem::path &name, std::vector<std::string> extra_qbsp_args,
+    std::vector<std::string> extra_light_args, bool run_vis)
+{
+    auto bsp_path = name;
+    bsp_path.replace_extension(".bsp");
+
+    std::vector<std::string> args{
+        "", // the exe path, which we're ignoring in this case
+    };
+    for (auto &extra : extra_qbsp_args) {
+        args.push_back(extra);
+    }
+    args.push_back(name.string());
+
+    // run qbsp
+
+    InitQBSP(args);
+    ProcessFile();
+
+    // run vis
+    if (run_vis) {
+        std::vector<std::string> vis_args{
+            "", // the exe path, which we're ignoring in this case
+        };
+        vis_args.push_back(name.string());
+        vis_main(vis_args);
+    }
+
+    // run light
+    {
+        std::vector<std::string> light_args{
+            "", // the exe path, which we're ignoring in this case
+        };
+        for (auto &arg : extra_light_args) {
+            light_args.push_back(arg);
+        }
+        light_args.push_back(name.string());
+
+        light_main(light_args);
+    }
+
+    // serialize obj
+    {
+        bspdata_t bspdata;
+        LoadBSPFile(bsp_path, &bspdata);
+
+        ConvertBSPFormat(&bspdata, &bspver_generic);
+
+        return std::move(bspdata);
+    }
+}
+
+void MainWindow::loadFileInternal(const QString &file)
+{
+    qDebug() << "loadFileInternal " << file;
+
+    auto d = QbspVisLight_Common(MakeFSPath(file), {}, {}, true);
+
+    const auto &bsp = std::get<mbsp_t>(d.bsp);
+
+    glView->renderBSP(bsp);
+}
\ No newline at end of file
diff --git a/lightpreview/mainwindow.h b/lightpreview/mainwindow.h
index 81cf2da9..776ca5ea 100644
--- a/lightpreview/mainwindow.h
+++ b/lightpreview/mainwindow.h
@@ -21,19 +21,29 @@ See file, 'COPYING', for details.
 
 #include <QMainWindow>
 
-namespace Ui
-{
-class MainWindow;
-}
+class GLView;
+class QFileSystemWatcher;
 
 class MainWindow : public QMainWindow
 {
     Q_OBJECT
 
+private:
+    QFileSystemWatcher *m_watcher = nullptr;
+    QString m_mapFile;
+
 public:
     explicit MainWindow(QWidget *parent = nullptr);
     ~MainWindow();
 
+protected:
+    void dragEnterEvent(QDragEnterEvent *event) override;
+    void dropEvent(QDropEvent *event) override;
+
 private:
-    Ui::MainWindow *ui;
+    void loadFile(const QString &file);
+    void loadFileInternal(const QString &file);
+
+private:
+    GLView *glView;
 };
diff --git a/lightpreview/mainwindow.ui b/lightpreview/mainwindow.ui
deleted file mode 100644
index e4eb7000..00000000
--- a/lightpreview/mainwindow.ui
+++ /dev/null
@@ -1,80 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<ui version="4.0">
- <class>MainWindow</class>
- <widget class="QMainWindow" name="MainWindow">
-  <property name="geometry">
-   <rect>
-    <x>0</x>
-    <y>0</y>
-    <width>499</width>
-    <height>423</height>
-   </rect>
-  </property>
-  <property name="windowTitle">
-   <string>MainWindow</string>
-  </property>
-  <widget class="QWidget" name="centralWidget">
-   <layout class="QGridLayout" name="gridLayout">
-    <property name="leftMargin">
-     <number>0</number>
-    </property>
-    <property name="topMargin">
-     <number>0</number>
-    </property>
-    <property name="rightMargin">
-     <number>0</number>
-    </property>
-    <property name="bottomMargin">
-     <number>0</number>
-    </property>
-    <item row="0" column="0">
-     <widget class="GLView" name="glView"/>
-    </item>
-   </layout>
-  </widget>
-  <widget class="QMenuBar" name="menuBar">
-   <property name="geometry">
-    <rect>
-     <x>0</x>
-     <y>0</y>
-     <width>499</width>
-     <height>22</height>
-    </rect>
-   </property>
-   <widget class="QMenu" name="menuFile">
-    <property name="title">
-     <string>File</string>
-    </property>
-    <addaction name="actionOpen"/>
-   </widget>
-   <addaction name="menuFile"/>
-  </widget>
-  <widget class="QToolBar" name="mainToolBar">
-   <attribute name="toolBarArea">
-    <enum>TopToolBarArea</enum>
-   </attribute>
-   <attribute name="toolBarBreak">
-    <bool>false</bool>
-   </attribute>
-  </widget>
-  <widget class="QStatusBar" name="statusBar"/>
-  <action name="actionOpen">
-   <property name="text">
-    <string>Open</string>
-   </property>
-   <property name="shortcut">
-    <string>Ctrl+O</string>
-   </property>
-  </action>
- </widget>
- <layoutdefault spacing="6" margin="11"/>
- <customwidgets>
-  <customwidget>
-   <class>GLView</class>
-   <extends>QOpenGLWidget</extends>
-   <header>glview.h</header>
-  </customwidget>
- </customwidgets>
- <resources/>
- <connections/>
-</ui>