Add boilerplate for shader based csg

sandboxes/opencsg/ShaderCSGDisplay.hpp

@@ -0,0 +1,26 @@
+#ifndef SHADERCSGDISPLAY_HPP
+#define SHADERCSGDISPLAY_HPP
+
+#include "Engine.hpp"
+
+namespace Slic3r { namespace GL {
+
+class CSGVolume: public Volume
+{
+    // Extend...    
+};
+
+class ShaderCSGDisplay: public Display {
+    vector<shptr<CSGVolume>> m_volumes;
+    
+    void add_mesh(const TriangleMesh &mesh);
+public:
+    
+    void render_scene() override;
+    
+    void on_scene_updated(const Scene &scene) override;
+};
+
+}}
+
+#endif // SHADERCSGDISPLAY_HPP