Comment by commandar
>Even with procedural and parametric modeling in Blender, you will always encounter issues with approximation and floating point precision, which are inherent to the data representation.
A common problem people run into with CAD models is importing a STEP file and modeling directly off of geometry in it. They later find out that some face they used as a reference was read by the CAD package as 89.99999994 degrees to another, and discover it's thrown the geometry of everything else in their model subtly off when things aren't lining up the way they should.
And that's with a file that has solid body representation! It's an entire new level of nightmare when you throw meshes into the mix.
The heart of any real CAD package is a geometry kernel[1]. There are really only a handful of them out there; Parasolid is used by a ton of 'big name' packages, for example. This is what takes a series of descriptions of geometry and turns it into clear, repeatable geometry. The power of this isn't just where geometry and dimensions are known. It's when the geometry and dimensions are critical to the function of whatever's being modeled. It's the very core of what these things do. Mesh modeling is fantastic for a lot of things, but it's a very different approach to creating geometry and just isn't a great fit for things like mechanical engineering.
> The power of this isn't just where geometry and dimensions are known. It's when the geometry and dimensions are critical to the function of whatever's being modeled.
Yes, but I meant making a case for workflow differences.
CAD is bad at aiding visual thinking and exploration, since you kinda have to be precise and constrain everything. You can pump out a rough idea of an object, edit it much, so much faster in Blender.
Sketching on paper, or visualizing in one’s mind, is pretty hard for most people when it comes to 3D. CAD is not at all inviting for creative impulses and flow. People who can do this in CAD are probably trained engineers who learned a very discipled, analytical way to approach problems, people who think in technical drawings.
So, CAD is good at getting a precise and workable digital representation of a "pre-designed" object for further (digital) processing, analysis, assembly and production. I think Blender is better at the early design process, figuring out shapes and relations.