Frame 3 Sharp


Open Source (MIT License) C# library for building 3D Tools in Unity.

Questions? Contact Ryan Schmidt @rms80 / gradientspace

What is this??

Unity is a great platform for games, but 3D tools are not games. Even the most basic 3D tools have much more complex, structured state. You might need different “modes” for different tools or operations, complex 3D user interface elements with state-dependent behavior, Undo/Redo, an easily serializable structured datamodel, and so on.

However, although every 3D tool has some kind of architecture that does these things, you won’t easily find one you can use to build your own tools. Keeping this kind of “3D tool shell” independent from the actual tool you are building is requires a lot of effort. Application functionality tends to bleed over into the infrastructure, to the point where the system is so tightly coupled that re-using the scaffolding becomes implausible.

I’ve done this 4 times myself. And I don’t want to do it again, ever. So, the purpose of frame3Sharp is an attempt to provide the “cad shell” infrastucture independent of any particular tool. I am building it on Unity to isolate the CAD-level aspects from the rendering/display subsystem (another area where coupling tends to creep in). Ultimately the Unity-specific elements will be abstracted, so that the system architecture could be ported to other rendering platforms (game engines, three.js, etc).

I am developing frame3Sharp to use in gradientspace products, first and foremost. However I do think that with the rise of distributed manufacturing - from mass customization to on-site medical device fabrication - there is a growing need for focused design tools that solve specific problems. My hope is that frame3Sharp will make this easy, or at least easier.


Frame3Sharp (F3) concerns itself with the management and manipulation of a 3D scene that contains a set of objects and interface elements, as well as a 2.5D “heads-up display”-type overlay of additional interface elements.

Objects in the 3D Scene

At the topmost level there is an FContext, you can think of this as the “universe” in which everything exists. An FContext contains an FScene, which then contains SceneObjects and SceneUIElements. The idea here is that a SceneObject is permanent - a cube, a sphere, etc - while a SceneUIElement is transient. So a 3D transformation gizmo would be a SceneUIElement, as would a clickable button that was in the 3D scene.

A number of SceneObject implementations are built-in. There are basic primitives like SphereSO and BoxSO, as well as 3D curves like PolyCurveSO and PolyTubeSO. PivotSO provides a way to represent 3D coordinate frames explicitly in the scene as manipulable objects. MeshSO wraps a unity Mesh, and provides functions for dynamic updates.

DMeshSO wraps a geometry3Sharp DMesh3 dynamic mesh, which can be arbitrarily large, and provides a rich set of operations for remeshing, deformation, and so on. DMeshSO automatically decomposes large DMesh3 meshes into a set of unity Mesh objects (limited to 64k triangles) for rendering. DMeshSO also provides a spatial data structure which supports efficient queries like ray-intersection and nearest-point on the entire mesh.

User Interface Cockpit / HUD

The FContext also contains a Cockpit, which manages the “near-field” user interface, which could be a 3D HUD in VR, or a set of layered 2D widgets in a desktop app. It is useful to think of this as 2.5D, and many of the objects work this way, with X/Y positioning (although in VR this might be X/Y on a cylinder or sphere) and Z as distance from the camera. The Cockpit elements are also SceneUIElement objects. The FContext maintains a stack of Cockpits, so you can “push” a new interface at any time.

3D widgets and Gizmos

A common paradigm in 3D tools is that when you select something, you get a gizmo that lets you do something with it - translate, scale, resize, etc. The TransformManager in FContext handles this. Gizmos are classes that implement ITransformGizmo, and once registered with TransformManager, will be automatically managed when the FScene selection-set changes. The built-in AxisTransformGizmo implements a standard move/rotate/scale gizmo, including transforming groups, rotation around arbitrary pivot points, etc. This gizmo is composed of Widget sub-elements, the idea is that these Widgets can be re-assembled into other Gizmos.


Another standard aspect of 3D tools is…the Tools. The FContext has a ToolManager which keeps track of which ITool is active. The set of possible tools must be registered with ToolManager at startup. Generally a Tool is modal, so when a Tool is active it takes control of the interaction to some extent. For example the provided DrawPrimitivesTool overrides the standard left mouse button behavior to draw primitives on left-click-drag. A separate Tool can be active on each input device, so if you are using VR hand controllers you can have a Tool in each hand.

Only a few Tools are provided, and writing a new Tool is a bit complicated. But we are working on abstractions, such as BaseSingleClickTool which allows you to easily implement a standard click-object-to-apply type of Tool with minimal code.


FScene exposes a ChangeHistory object which implements standard undo/redo behavior via IChangeOp objects that apply/revert changes to the scene. A set of standard change operations are provided to enable undo/redo of add/delete objects, change materials, editing of primitive parameters, and 3D transformations. This is built in to the existing Tools and Gizmos, so for basic interfaces Undo is effectively “free”.


If you’re using a mouse, you generally have a 2D cursor. In Touch-based interfaces, you also have a cursor, although it behaves a bit differently. And finally in a VR app you might still want to use the mouse (gasp!), or a gamepad to control an on-screen cursor. FContext abstracts these different options via an ICursorController, which tracks the cursor and defines things like how the 2D cursor location maps to a 3D ray into the scene. SystemMouseCursorController, TouchMouseCursorController, and VRMouseCursorController provide implementations for the common cases.

3D Spatial-Input Controllers

VR controllers like the Vive wands and Oculus Touch break the standard 3D tool paradigm in many ways. The most immediate is that you can have two simultaneous “cursors”, attached to tracked hand controllers. When using VR, and such a device is active, FContext provides a SpatialInputController class that tracks each hand and a 3D cursor/ray in the scene. Much of F3 already supports these devices, such as having two tools active at the same time.

Behavior System

One of the most complicated aspects of 3D tools is managing the huge input-device state machine that is built up over time. Even a relatively basic CAD tool has lots of different interactions - camera controls, selection, moving things around, drawing and editing tools, etc. Often this degenerates into a spaghetti of checks and branching.

F3 attempts (attempts!) to simplify this with its Behaviour system. FContext has a top-level InputBehaviorSet which collects InputBehavior objects from the scene, cockpit, and active tools, and determines how each input event should be handled. Any input events are converted to InputState events, which provide both abstract and low-level access to input device buttons, joysticks, postions, etc.

An InputBehavior might be something as simple as a MouseMultiSelectBehavior, which selects objects on click, or as complex as an entire 3D camera control system. InputBehaviors can be written separately for different devices, for example TouchViewManipBehavior and MouseViewManipBehavior, and SpatialDeviceViewManipBehavior each provide camera controls for the relevant input type. F3 handles this all internally, you just have to write and register your InputBehaviors.

The behaviors folder contains a variety of standard behaviors, and some useful abstractions such as MouseClickDragSuperBehavior, which allows you to implement click-release vs click-drag actions as separate InputBehaviors and them compose them.

UI Elements

Anything can be turned into an interactive user interface element by implementing SceneUIElement. Interactive 3D elements in the scene, like Gizmos, implement this. So do the 2.5D HUD UI elements in the Cockpit, which are in fact also full 3D objects, just positioned relative to the eye rather than the scene. As a result they can easily be used in 2D desktop apps, VR interfaces, and placed directly in the 3D scene.

We are implementing a standard set of UI elements - HUDLabel, HUDButton, HUDTextEntry, and so on, as well as containers such as HUDPanel and HUDElementList. A box-model layout system is in-progress. To display Text, Unity TextMesh objects are used, and optionally TextMeshPro support can be enabled for higher quality text rendering.

The Unity 2D canvas system is not used by these UI elements. All elements are standard GameObjects.


The set of current SceneObjects can be stored by SceneSerializer to an IOutputStream (XMLOutputStream is provided), or restored via IInputStream. You can support store/restore of custom SO types by registering serialize and build functions with the SORegistry stored in the Scene.

SceneMeshImporter supports reading in mesh files at runtime as MeshSO objects (DMeshSO support coming soon). Any format that geometry3Sharp supports can be read, and for OBJ files, materials and texture maps will also be loaded. Similarly SceneMeshExporter can export any SOs that contains Meshes.


animation, plugins, util, unity interop


I use this project exclusively as a git submodule, so the structure/etc is set up to make that easy. You just add frame3Sharp as a submodule with a local path inside the /Assets folder of your Unity project directory.

Currently this project is not usable outside of Unity. Someday!!

Scene Setup

  • main camera must have tag MainCamera


frame3Sharp includes several small external libraries to provide access to OS functionality inside Unity (which is otherwise not available). These are pre-compiled and included as DLLs/bundles/etc in the \Plugins folder

  • tinyfiledialogs is a cross-platform library with zlib license that can show native file open and save dialogs.


frame3Sharp is built on several other libraries/components which are not included in this repo. These need to be added to your Unity project yourself. Or, you can start with one of the samples in the frame3SharpSampleApp repository, which does include these other projects.

  • geometry3Sharp github. This C# codebase should be included in your project as code (or possibly a compiled DLL, but that is currently untested)

  • DOTWeen Unity package link. Also available in the Unity Asset Store, for free. Used for animations in some places. Removable with minor effort, if you prefer. This dependency will likely be removed in the near future

  • Oculus Utilities for Unity 5 link. Because frame3Sharp is designed to support VR, there a few classes that must access the OVRInput to enable use of Oculus Touch controllers. Currently these files are not included, so you must install this component in your project, or delete any references to OVRInput in the code (affects 3 files, which are not used if you are not using VR).

Documentation / etc

will come in time!