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Comment by criddell | Hacker News Reader

Would either Godot or O3DE be a good choice for a CAD-type application? It looks like Godot deals well with a scene graph which seems like a good way to organize data for that kind of application.

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Neither is designed for a CAD engine. CAD uses generally NURBS and a scene graph based around constraints. Game engines are not constraint based but rather about independent behaviour agents interacting using triangle meshes. Quite different.

Interesting! Is there any game engine or open source engine or library that would support those kinds of code styles?

For NURBS modelling there is OpenNURBS [1], made by the guys who made Rhinoceros 3D, an excellent NURBS 3D modelling program. However, although Rhino is available on Windows and macOS, it is not available on Linux and the authors seem pretty against making a Linux version. OpenNURBS is only available on Windows.

[1] https://www.rhino3d.com/opennurbs/

I personally use MoI3d (http://moi3d.com/). It is basically Rhino but cheaper (albeit with less tools and features).

But as an Indie dev it gets the job done for me.

I desperately want open source CAD to be a thing. I would suppose that Freecad is probably a very good starting point. I don't think the lack of good open source CAD is due to a lack of a decent codebase so much as the fact that good CAD software is a very large project and we have just not directed enough efforts towards it. I am speculating however and may be wrong.

Rather than "just" Open source CAD I would like to see Open Source CAD-like applications. Well, at least in my mind CAD is something kind of specific and carries a lot of design assumptions with it.

I feel there is a lot of cool stuff you can build in the space of building shapes using constraints. Like visual programming languages made to visualize mathematical relationships using geometry.

Interesting. In my case I am specifically talking about mechanical design CAD for engineering. We have a huge need for that in my opinion. Freecad might be the closest thing but I suspect it needs more investment.

However what you’re talking about sounds important as well.

> I don't think the lack of good open source CAD is due to a lack of a decent codebase

I think the problem is exactly that. A good constructive solid geometry (CSG) is a difficult thing to make and there are no open source alternatives to the ones powering the mainstream CAD packages.

Closest thing would be a level editor, which is very much a CSG-based CAD program with roots going back to the Quake 1 generation. It's just not geared towards typical production applications where real objects are being machined.

Did it have boolean operations like add, subtract, and cut?

Yes, along with the usual extrusion and (I believe) lofting along a desired path.

(I have not looked so this is a genuine question)

Is there an actual issue with the freecad codebase? It has always seemed relatively functional.

It's hard to avoid the segfaults. I've tried to use it many times for simple projects. Some workflows it's every 10min or so, and often you get into corrupted states where you can tell it's about to happen, but of course if you save you risk your files completely.

It's also slow, onshape in my browser beats it at roughly everything.

Graphics-wise, the assumptions are quite different. Game scenes are a large collection of low-detail objects that are constantly moving and not all visible at once. CAD scenes are a small collection of high-detail objects that don't move except in response to input events.

If the CAD project is big and serious, I would be afraid of eventually hitting some limitation of the game engine that is hard to work around due to such different assumptions.

Both game engines and CAD applications have some type of level of detail node in their scene graph so that zoomed in items are high fidelity and items further are simplified.

You would want something like OpenInventor instead.

https://www.openinventor.com/

Is that related to Autodesk's Inventor at all?

I work on an application that uses the geometry kernel from PTC (GRANITE) for modeling and OpenSceneGraph for display. I'm a little worried about OpenSceneGraph because it's 100% OpenGL which feels like it's at the end of it's life and we need to find something built on Vulkan or Direct3D for the future.

Nope, it was born as IRIS Inventor, the actual crown jewel for SGI, when they let IRIS GL turn into OpenGL, they kept it for themselves.

https://web.archive.org/web/20041120092542/http://oss.sgi.co...

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