> On Oct 10, 2026, at 6:12 AM, maurice e heskett <[email protected]> wrote: > > On 10/10/26 07:42, Robin Szemeti via Emc-users wrote: >>>> Think of it this way: You are Michelangelo carving a statue of David
OK, let’s make the example more relevant to CAD. Let’s say you are an architect, not a machinist. Architects are also big CAD users. But no architect would ever, even once in his life, use G-code or OpenSCAD to design a shopping mall. So, a simple use of 3dCAD that shows parameters. The designer thinks a fake column along a wall might look nice. So he draws a circle on his screen and then a vertical line to cut it in half. Next, he erases half the circle and ends up with the letter “D”. Next, he specifies a dimension of 24 inches for the flat side. Then, finally, he places the “D” on the floor and pulls it up to make a “half column.” Then he sticks it on a wall. Then he duplicates the half column 50 times along the walls. Finally, he asks the software to make a photo of the building for his client. The client says “columns are too small.” Finally, the parametric part: The architect sees all of the columns “depend” on the first one (because they are all copies) and the first column depends on the letter “D” drawing he made. He sees that the “D” is 24 inches across. He changes the 24 to 36. Next, the software changes every column to be 36 inches wide. You can say that each of those 50 columns “depends on a parent dimension.” Next, the client says “I like the size, but I’ve always liked those classical-looking fluted columns.” So the architect changes the “D” to no longer have a smooth arc and makes a more complex shape and saves it. As soon as that sketch is saved, every column in the project updates to the more complex shape. Of course, it is more complicated; the columns were not just made at some random height; the designer said to pull them to the ”wall height.” And then when he changes “wall height,” everything that depends on that changes: the roof moves up, the volume of concrete needed changes, and so on. It is surprising how few dimensions one uses when building with CAD. Think of a house. Where do the ceiling joists go? You’d be place each one “8 feet above the floor,” because then when the client says he wants a 100-inch ceiling, you would have to move 300 ceiling joists. SO, the smarter architect says, “The ceiling joist goes on top of the wall and makes direct contact with it.” Now when the wall height changes, everything on top of it moves. How long are the wall studs? Ceiling height minus the top and bottom rails. You use fewer numbers than you’d think. >> from a rock. There is no text file, only rock. Then 500 years later >> someone uses a laser to digitize the statue. This is how 3D CAD works: >> you make an object, then maybe you need an STL file so you can print it; >> the software uses lasers or whatever to measure the object and make an STL >> file. >> >> This is entirely incorrect, this is exactly how 3D CAD does not work ... >> what you are describing here is nothing more than a capture of an object, >> an uneditable rendering. >> >> 3D CAD captures the design intent, a series of decisions and dependencies, >> and from those decisions and dependencies it creates the object. A much >> better way of thinking of 3D CAD is: >> >> You are Michelangelo carving a statue of David from a rock. You have >> kept a detailed notebook of sketches, instructions, notes about the the >> relative measurements of the statue, the angles of the arms and legs, the >> details of how the skin surfaces are smoothed from the limb joints etc, >> everything you need to create exactly the finished work again from another >> lump of rock, even if the orginial is lost and no one even has an image of >> what it looked like. Essentially there is no rock, only the notebook, the >> text file. >> >> 500 years later, someone can perform the same task, but they can alter any >> of the design decisions or angles, or parameters used to smooth skin. >> >> The crucial thing to remember is the CAD file usually does not store the >> object at all, it stores the set of instructions (th source code if you >> like) to create the object when that set of instructions is fed into a >> suitable tool that can interpret them (run the code) and build the object >> from scratch. > That sounds like you are agreeing with me. Thank you. >> >> On Sat, 10 Oct 2026 at 04:26, maurice e heskett <[email protected]> >> wrote: >> >>> On 10/9/26 18:02, andy pugh wrote: >>>> On Fri, 9 Oct 2026 at 22:25, Chris Albertson <[email protected]> >>> wrote: >>>>> Next problem is the FreecAD just happens to have the worst user >>> interface of any 3D CAD system. It works, but the user experience is >>> poorer than with other systems. >>>> I have used worse, but it was a while ago. And I am prepared to >>>> believe that there are worse out there. But that video seems to >>>> suggest that it's improving fast. >>>> >>>> Arguably OpenSCAD is worse, depending on how you define "user interface". >>> Debatable. I like the text src I can see and edit in real time, but find >>> the editor a bit clunky. >>>> But I am not necessarily disagreeing with your statement. I can't say >>>> I am enjoying my ideologically-based switch from Fusion to FreeCAD. I >>>> am not finding myself modelling for fun in quite the same way. >>>> >>>> But I _am_ confident that _my_ models remain _my_ models and will >>>> always work with the version of FreeCAD on _my_ computer. >>> The latter Exactly, Andy. > Cheers, Gene. >>> >>> _______________________________________________ >>> Emc-users mailing list >>> [email protected] <mailto:[email protected]> >>> https://lists.sourceforge.net/lists/listinfo/emc-users >>> >> _______________________________________________ >> Emc-users mailing list >> [email protected] <mailto:[email protected]> >> https://lists.sourceforge.net/lists/listinfo/emc-users >> . > > > _______________________________________________ > Emc-users mailing list > [email protected] <mailto:[email protected]> > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
