Jump Right In

If you just want to grab the current installer, here you go: Cotangent2_Beta2.exe (Win 10/11, posted June 23, 2026).

What Does Cotangent 2 Do?

Cotangent2 is a new 3D triangle mesh editing app, in the spirit of Autodesk Meshmixer (RIP, 2008-2016). I (Ryan Schmidt, @rms80) initially started developing Cotangent2 for Meshmixer users who are working in the Medical CAD space. Even though Meshmixer has been abandoned for nearly 10 years now, it is still widely used by doctors, dentists, prosthetists, and in many other medical-related domains. In this space I’ve heard many feature requests that I believe will never be satisfied by the Fusion 360 Mesh Workspace (which is where Autodesk redirects Meshmixer users). In this intervening decade, no other software has provided a comparable easy-to-use mesh editing environment. And so my initial focus with Cotangent2 was on this userbase.

I started with much-requested features complementary to Meshmixer, like better Measurement and Analysis tools, 3D Text Labelling of meshes, and better mesh auto-repair. Cotan2 leverages the fantastic realtime mesh geometry kernel in Unreal Engine to implement many “better” versions of Meshmixer Tools, and I also took advantage of the substantial toolbox of geometry algorithms in Gradientspace’s C# geometry3Sharp library. And there is “Meshmixer Sync” functionality to help the apps work together!

Pivot to AI-Based Tools

Cotan2 development kind of stalled in 2025 because I was focused on Gradientspace Graph. However the advent of Claude Code radically changed the prospects for general-purpose nodegraph programming (😢). And so in the spring of 2026 I shifted back to Cotan2, leveraging Claude Code to make rapid progress (it’s really good at UE5’s Interactive Tools Framework, which I use heavily in this app). I started experimenting with local AI models like SAM2/SAM3 image segmentation (via the great sam3.cpp open-source library) as well as local Image Generation/Editing models (via leejet stablediffusion.cpp). Based on these models I implemented some pretty neat automagic-mesh-selection and texture editing capabilities, that can run locally on a modest GPU (8GB VRAM).

Current Toolset

Here is a brief summary of the current Feature Set and Tools:

Import/Export - OBJ, STL, and GLB meshes. Limited support for GLB materials, and currently only the first mesh in a GLB file is supported.
Scene Saving/Loading - Save/load to a binary Cotangent file format. Under the hood, this is a standard sqlite3 database with meshes serialized as simple binary blobs in an open format. So your data will never be trapped, like it was in the .mix format.

Modeling Toolset

Duplicate - make a copy of a mesh
Combine - append meshes together
Split - separate mesh by connect-component or facegroups
Select - improved version of the brush-based triangle selection you know and love
AI Select - automagic part selection based on SAM2/SAM3 AI models running locally on your computer (*)
Sculpt - adaptive mesh sculpting (this one is a bit rough…)
Plane Cut - robust battle-tested mesh cutting with Delaunay Triangulation of holes
Boolean - “quite-robust” precise mesh Boolean operations
Remesh - fast split/flip/collapse remeshing with various criteria/controls
Make Solid - a much-improved algorithmic approach based on the Fast Mesh Winding Number [ blog1 ] [ blog2 ]
Weld - weld mesh open boundaries, and also resolve T-junctions
Fill Holes - fill holes in meshes w/ various strategies
AutoRepair - mesh-based methods to remove holes and repair other mesh issues
Measure - measurement of dimensions and radius
Section - section plane analysis
Compare - various type of comparison visualizations between meshes (eg compare before/after edits, etc)
Label - add 3D text to meshes

Texture Toolset

Auto UV - automatically generate UVs using PatchBuilder algorithm (for entire mesh or areas-missing-UVs)
Tex Util - various texture utility tools including rescale & expand texture space
Mat Util - create new material+textures (eg for untextured meshes)
Pixel Paint - paint individual texels on a mesh, in 3D
Texture Paint - paint mesh texture using a 3D brush
Live Stamp - place/manipulate Texture Stamps, and then stamp `em
AI Stamp Edit - edit textures using AI Image-Edit Models, either Local (*) or via APIs, via a local unwrapping (that’s the ‘stamp’ aspect)
AI Project Edit - edit textures using AI Image-Edit Models, either Local (*) or via APIs, via image-space projection & brushing
Feature Eraser - magic mesh+texture feature removal & repair using AI Image-Edit models

Meshmixer Sync

Cotan2 can import the current scene from an open Meshmixer instance, as well as push updates back to Meshmixer. We know that many professionals are actively using Meshmixer in their labs, clinics and practices on a daily basis, and can’t just up and switch to some other software that doesn’t have all the necessary capabilities. So we’ve made it as easy as possible to use Cotan2 as a sort of “Meshmixer Assistant”, providing missing features or more robust/capable versions of critical Tools without requiring you to fundamentally change your Meshmixer-based processes.

Oh BTW you can still download Meshmixer for Windows and Mac, check out meshmixer.org for details.

Download / Installation / Setup

A Cotangent 2.0 Installer for Windows 10/11 is available here: Cotangent2_Beta2.exe . This version was posted June 23, 2026.

OptionAL: Install .NET 8 Runtime

Some (optional) tools in Cotangent 2.0 are implemented using C# and hence require that you install a version of the .NET 8.0 Runtime. Currently this isn’t bundled in the installer, and you can skip this if you like (nothing bad will happen, the associated Tools just won’t work). Here is a direct link to the 8.0.21 installer, or you can go to Microsoft’s .Net 8 page and scroll down to the .NET Runtime section and follow the link for the current Windows x64 version. (There is a good chance your computer already has this installed, but it won’t hurt to make sure)

AI Model Weights & API Services

FUTURE Development

Future development of Cotangent 2.0 is up in the air right now.

Cotangent 1.0

Cotangent 1.0 was 3D Printing and Mesh Repair software that Gradientspace Corp developed from 2016 to 2018 - it’s still on the web here, for now. As of November 2025, we’re rebooting this project, starting from scratch and with a somewhat different focus. This page will serve as a home for the new version until we rebuild the main website.