If I remember in autocad you would have to use a command redraw the view, at a certain point the curves wouldn't be smooth at all.

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"Regen" or "Regen All" for regenerate the drawing.

I don't at all know how this stuff works under the hood but I wonder if AutoCad uses a different system of math than more modern programs. They tried for years to keep up with the parametric 3d programs by glomming tools on top of basic ACad but in the end had to write Inventor from scratch and buy Revit, Maya and Mudbox. It is easier now for sure to work in ACad 3d but you still have to move the UCS around to draw at an angle.

Anybody able to explain in layman's terms what changed over the years? Does it have anything to do with floating point math? Or maybe how 3d space is defined?

I'm just curious.

ch

Hi unclecharlie, as far as I know AutoCAD does not use any special system of math and does not actually have unlimited zoom. It's not particularly feasible to have unlimited zoom in any CAD program because there is a fundamental limit to accuracy based on how much memory is devoted to storing a number.

> Anybody able to explain in layman's terms what
> changed over the years?

What change are you talking about? Not much has changed in the basic geometry handling of AutoCAD...

You still have to use the regen command in AutoCAD, at least with AutoCAD 2008 which I just tested with. For example draw a small circle on the screen then zoom in to it, after zooming in you'll see the segmentation in the circle which will go away if you use the Regen command.

That's just how AutoCAD's display system is designed, it sets up a kind of static representation of the wireframe of the model and doesn't try to adapt the density of lines on the fly. Other programs like MoI which don't need a regen command are actually constantly recalculating the set of lines that make up a curve's visual representation at every screen redraw, that's what eliminates the need for a special regen command but if you go back to computers 30 years ago (where AutoCAD has its roots) they were a lot slower than they are now and it was hard to make things do dynamic calculations.

- Michael

"What change are you talking about? Not much has changed in the basic geometry handling of AutoCAD..."

I'm actually asking about the changes that allow other programs to do things like parametrics and dynamic re-assignment of the drawing plane that AutoCad can't do. It just seems to me that they are stuck with some core functionality that they can't really improve on in an efficient manner, so they end up buying newer companies in order to keep up with the competition. I'm guessing that the way the math is handled at the base level is what they are stuck with and if they changed that they would break everything else.

I teach AutoCad, Inventor, Revit and Sketchup at the technical college level. (I got interested in Moi in order to learn about nurbs based modeling in case students start asking about it. Everybody wants to be a car designer!) AutoCad has reached the point where they continue to change the interface year after year without actually improving the efficiency. I wish they would just leave it alone, but that doesn't sell new copies of the software.

Hi unclecharlie,

> I'm actually asking about the changes that allow
> other programs to do things like parametrics and
> dynamic re-assignment of the drawing plane that
> AutoCad can't do.

Well, those changes would most likely be just raw speed increases in the computer hardware.

In general things that are dynamic and more graphically intensive also require more CPU cycles to make them happen, and 30 years ago when personal computer CPUs were much slower than they are now that would have an impact and tend to limit the software design more.


> It just seems to me that they are stuck with some core
> functionality that they can't really improve on in an
> efficient manner, <...>

Yeah, that is a pretty common problem - sometimes older programs become complex over time with layers of stuff built on each other and when things get to a certain size it is a really big job to try and alter various kinds of lower level things. Or I should say it's a really big job to alter such things without causing a large number of bugs from various other parts of the program that assumed that things were structured in one particular way...


> I'm guessing that the way the math is handled at
> the base level is what they are stuck with and if they
> changed that they would break everything else.

I don't have any information about it specifically, but it's not necessarily anything to do specifically with math handling, it's just easy for quite a lot of additional code (including code from other companies as well when you have 3rd party extensions going on as well) to have dependencies on the existing overall design, and trying to change that design would require a ripple effect of changes needed to a lot of other code as well.

- Michael