topic Re: Linetype spacing incorrect at ends in Visual LISP, AutoLISP and General Customization Forum

Linetype spacing incorrect at ends

hencoop — Thu, 31 Aug 2017 20:13:16 GMT

Hello all,

This has been a problem for me for years. I was hoping that someone would know more bout it and perhaps even have a solution for it.

I have custom DOT linetypes with a very specific spacing (when both LTscale and the object linetype scale are 1.0). The spacing is critical as they are used in my profile grids and the dots coincide where grid lines intersect. If the pattern is off then the result is a somewhat random dot pattern. The dots have multiple purposes. One is to have dots that mark off standard measurements along both the horizontal and vertical grid lines. Another is to have black dots that appear to print as a gray line because of the white space between the dots. Yet another is to permit using the very compact compressed TIFF bi-tonal raster format as the plotter output because it neither makes the grid lines solid black or solid white but instead makes black dots where they are in the linetype definition.

Here is the linetype definition and an image of the incorrect spacing that is at each end of the lines:

*dot3d,dotted line ..................................
A,0,-0.066667

Re: Linetype spacing incorrect at ends

lando7189 — Thu, 31 Aug 2017 21:03:23 GMT

That is just how linetypes are -- the ends 'average out' the remainder spacing.

To get what you want, you could create a dynamic block using a linear array parameter that could array a block or an entity of somekind (a small line or circle or donut).

Re: Linetype spacing incorrect at ends

hencoop — Fri, 01 Sep 2017 02:18:32 GMT

Thank you for your reply. That is not my experience. The line lengths are very carefully set to an even multiple of the dot spacing yet they have improper spacing at the ends. I think line types are much more efficient at this than arrays and dynamic blocks. I mask the ends now. I was hoping there had been some improvement I had not heard of.

Re: Linetype spacing incorrect at ends

Kent1Cooper — Fri, 01 Sep 2017 11:25:34 GMT

@hencoop wrote:
.... The line lengths are very carefully set to an even multiple of the dot spacing yet they have improper spacing at the ends. .....

But the dot spacing is a rounded-off value [-0.066667], so careful setting of the lengths isn't ever going to meet it exactly. What if you tried defining the spacing as a "clean," "exact" value, such as -0.1, and then used it at a linetype scale to get the resulting spacing desired?

Re: Linetype spacing incorrect at ends

hencoop — Fri, 01 Sep 2017 11:43:01 GMT

Hi Kent,

It is unfortunate that I have used my linetype for 30 and 60 scale grids as my example but I have the same problem with dot spacing set up for 50 scale which is very clean and exact. Perhaps this is another of those things that go unnoticed, unreported and never repaired because typical users have never used linetypes to produce a specific dimensional spacing of their "pen down" specifications or they just don't care if the ends of their linetypes are just a bit different. This happens to ALL linetypes, dots or otherwise. Maybe I'm the only weirdo that uses linetypes like this.

Re: Linetype spacing incorrect at ends

lando7189 — Tue, 05 Sep 2017 19:39:00 GMT

Here is a quick example i did up -- the spacing is 10, but just scaling it by 5 would make the distances 50... 6 would be 60, etc.

Re: Linetype spacing incorrect at ends

hencoop — Tue, 05 Sep 2017 19:46:37 GMT

Thank you for your reply.

That does work nicely and does not exhibit the problem that linetypes do; however, my purpose was not to find a workaround (I have that) but rather to bring the problem to Autodesk's attention and hopefully have them fix this problem with linetypes permanently.

Re: Linetype spacing incorrect at ends

lando7189 — Tue, 05 Sep 2017 20:25:07 GMT

Aha... i just realized the problem. I have a dotted line with 0.25 spacing, and have a length of 1, i get 5 dots -- nice and clean.

But when i make a linetype definition of the type you specified, i get the ugly gaps at the end.

In your case, the distance is 0.066667 -- which is ever so slightly more than 1/15th. To fix it, change the definition to:

A,0,-0.066666,0,-0.066667,0,-0.066667

... and now your lines can be exact in length.

Re: Linetype spacing incorrect at ends

lando7189 — Tue, 05 Sep 2017 20:26:22 GMT

My original post above was wrong (fixed now)... the smaller 'pen up' values have to come first:

A,0,-0.066666,0,-0.066667,0,-0.066667

Re: Linetype spacing incorrect at ends

hencoop — Tue, 05 Sep 2017 20:37:16 GMT

You had my hopes up. I had not tried doing multiple pen-up pen-down definitions in a single dotted linetype. Alas! it is still the same with your fixed definition. (This line was set at exactly 3.0 units and then 1.0 units and both look like this).

Re: Linetype spacing incorrect at ends

lando7189 — Tue, 05 Sep 2017 20:41:21 GMT

Yah... i found out the second gap goes over again...

So, for an exact line, it would be:

A,0,-0.066666,0,-0.066666,0,-0.066668

But, since you were OK with 0.066667, just 0.066666 should be good enough. So the secret is just not to go over!

A,0,-0.066666

Re: Linetype spacing incorrect at ends

lando7189 — Tue, 05 Sep 2017 20:48:10 GMT

Oh -- linetypes have to be reloaded into the drawing (otherwise, the definition stays whatever it was at the time it was loaded -- that is how you can distribute files with custom linetypes without having to send a linetype file).

That actually would fix your problem you just posted -- (my suggestion about the smaller 'pen up' values would only affect certain 'fractional' length lines)

Re: Linetype spacing incorrect at ends

hencoop — Tue, 05 Sep 2017 20:57:42 GMT

I really appreciate your working on this. I have reloaded my linetype and I have calculated the exact length the line should be for a given number of iterations of the pattern. I set my line to that exact length but yet again I am sad to report it looks like this (my last test was actually 0.0001 units shorter than the definition called for):

There is ALWAYS a gap of about half again the defined pen-up distance at each end regardless of what you or I do. Your efforts have reaffirmed my years of experience with this problem. I had so hoped you were right. Thank you again for looking at it.

Re: Linetype spacing incorrect at ends

hencoop — Wed, 06 Sep 2017 15:23:12 GMT

@lando7189 Yours is a good solution to creating a measured dot matrix from linear arrays in dynamic blocks even though it does not specifically solve the longstanding "incorrect spacing at linetype ends" problem. I hope that Autodesk will address this linetype problem at some point but I'm not holding my breath. For those visiting this thread that may want this effect and have experienced the linetype problem like I have, your solution does it nicely I think.

Re: Linetype spacing incorrect at ends

jmay1 — Thu, 31 Dec 2020 20:24:29 GMT

You're not the only weirdo. I would also like very much for Autodesk to fix this problem. I want my dots to line up exactly. I had to create a dynamic dot matrix. It works great but I still want them to fix the linetype problem.

Thanks!

Re: Linetype spacing incorrect at ends

Thomas_ConnollyMQNNG — Wed, 13 Mar 2024 10:11:12 GMT

I was having a similar issue with Hidden linetypes not evenly spacing at the ends.

Never happened to me before, and it was driving me mad. I know with Polylines you have the LTGEN variable, but these are regular normal Lines!!!!!

Google searching got me to try 'GRAPHICSCONFIG'

I was on a new laptop running AutoCAD LT 2024 and the Graphics Performance setting was 'Advance Mode'.

I changed it to 'Intermediate Mode' and now my regular hidden Lines look correct again.

It's a miracle!