History of DEFPOINTS

[elibraffback]

Looking for anyone who can explain WHY defpoints is the name of the layer that cannot print. Is "def" short for something? Is def a prefix? 

What does this name mean (aside from its purpose) and how did it come about?

Thanks.
Eli

[Anonymous]

Def is most likely short for definition. It's created when you place a dimension on your drawing and it contains the points that define the location of your dimension start and endpoints. If you are familiar with grips when you select a dimension the defining points will display a blue box at those locations.

[Alfred.NESWADBA]

Hi,

I don't know if you really get an answer, because that can only give that guy who developed that part.

From my understanding and remembering: defpoints means "definition points" for dimensions like anchors between the geometry to be dimensioned and the dimension object so it can be associative.

- alfred -

[Kent1Cooper]

See >this Post< for some explanation, and for why it's not a good idea to use for anything other than DEFinition POINTS for Dimensions, as well as the fact that it is not [for many years now] "the"  Layer that cannot print -- you can make any  Layer not print.

[cadffm]

Systemlayer for the system (incl. Layerproperties like unlock,on,thaw)
except Layer0 for special constellations for Block and Xrefs Objects.
Systemblocks only for using, not to editing.

And best practise. All pre defind Systemstyles for no one.

And for users are the userdefined styles, layers and Blocks.

And you get fewer trouble as some old guys (which wants never will learn)

[dgorsman]

The "why" is far less relevant than the "what" - it could just as easily be called Fred or Wilma.  It's just an arbitrary hard-coded value, same as "0", "Standard", or "2D Wireframe".

[Ranjit_Singh2 · Accepted solution]

Whichever layer you create the dimension on, it will always add some points to the defpoints layer. These are pretty much the definition points which are used to calculate relevant distance and placement. Defpoints layer makes sure these entities don't plot.

In case of below linear dimension you get 3 points on defpoints layer.

For radial dimensions you get 2 points; one at center and one at circumference. Same for diametric dimensions, etc. I am guessing back in the days they did not have advanced functionalities (for ex. reactors) to tie dimensions to entities. So points were maintained to pull distances from and has continued to be that way? Just my guess.

[scot-65]

Someone that has been around longer than me may need to verify
that prior to release 12 (not R2012) there was no defpoints layer.
Or was it 10?

Back then, pen plotters were the norm and the dimension
definition points was not on defpoints. What happened was the
pen knocked on the paper like a woodpecker to a tree when there
was many dimension definition points in one place. I remember
once the paper was actually cut open because many (dimension)
lines stacked on top of each other and the pen would keep traveling
back and fourth in one area (pen plotters that rolled the paper back
and fourth while the pen traveled left and right is what we used).

???

[Kevin.McCarthy]

I've been around a while but that's a conversation for the pub !

Dims used points these like other points were under the influence of PDMODE and PDSIZE if you set PDMODE to something other than 0 and a size specific or as a percentage of screen height you would get crosses or circles etc at the ends of all your dims. Not a good look on a plotted drawing. You would just set PDMODE 0 and they would all turn to dots. That's great unless you wanted to plot other points in your drawing and plot your dims also. So to get around this problem the points created for dims had their own layer DEFPOINTS that would never plot so you could plot other points and your dims without points at the end of your dims.

I believe the Advanced Modelling Extensions also used that layer and maybe even hatch. All this has been tidied up over the years and you wouldn't go about developing a CAD package in this way now.

Historically it was all very much a first generation CAD package for the recently released IBM PC. On reflection AutoCAD won that race because it was being developed quicker than any other product, felt like two release a year in some years. Its was very much a race for companies to say that they had embraced this new technology. In hindsight some things could/should have been done better. Its was simple and effective though.

Regards.

Kevin.

[GrantsPirate]

Looking in my AutoCAD R10 book there is a section on Definition Points (defpoints) used for dimensions.  I found no mention of them in the R8 book and don't have an R9 book to check.   The layer had to be off to keep it from plotting.  The R12 book talks about defpoints not plotting whether they are on or off and that is when so many of us started using defpoints layer for other things we wanted to show but not plot.

From 2018 help file

Note: Definition points are created on a special layer named DEFPOINTS that is never printed or plotted.

[Alfred.NESWADBA]

Hi,

>> no mention of them in the R8 book

Can you show a photo from that book?

Just curios because there never existed a version 8, there was a jump from version 2.63 ( to be more specific, I think it was 2.63h) to release 9.

But there are more people out there refering to a release 8, so it would be great to see that 😉

- alfred -

[cadffm]

I think 2.6n =IS> Release8

[GrantsPirate]

2.6 = R8

http://autodesk.blogs.com/between_the_lines/autocad-release-history.html

[leeminardi]

I was working for a competitor when the first version of AutoCAD was released. AutoCAD did not support associative dimensioning.  That is, modify geometry and the dimension line values automatically update. CAD systems that did support associativity  had database pointers between dimension lines and the geometry referenced to create the dimension line.  Autodesk was under pressure to feature associative dimensioning so they implemented what some would call a QAD solution.  Rather than make a major change to the database to provide associativity they decided to place a point at the reference point used for the dimension line. Placing the point on a special layer was a fudge that made implementation easier.  In this way the user's selection window is used to create the appearance of associativity between geometry and the extension line component of a dimension line.  In later releases additional links were created between dimension lines and geometry but  the associativity is still weak at best.

Try the following, create a line and dimension it with a linear dimension using osnap end.

Use move to move the line by selecting the line near its center. The dimension line will follow even though the def points were not selected. Now delete the line and the dim line will remain (it shouldn't). Undo. Now move the dim line, the geometry line will not follow. Undo.  Give the stretch command and a select cross window (right to left) over one end of the line and specify a displacement with two points.  The line and the dimension line stretch accordingly and the dimension value updates too.  Here, the associativity of the line and the dim line is achieved via the def point.  

Compare the above behavior with a true associative dimensioning features as found in the parametric functions or Inventor sketching.

[Partenheimer]

From AutoCAD 2019 Help - Glossary of AutoCAD Terms:

http://help.autodesk.com/view/ACD/2019/ENU/?guid=GUID-C4325DCB-3648-4463-8135-629EA7F72AB0

definition point

A node located at the end of an extension line corresponding to the location on the object being dimensioned. Definition points, also called defpoints, are stored on the reserved, non-plotting Defpoints layer.