Dimensioning drawings
Good morning,
This question relates to modelling philosophy for dimensioning and annotating drawings. I am interested on the methods different people use to work with paperspace layouts, dimensions and mutlileaders to see if there are more effective ways to use them.
Generally when I am drawing 2D models my preferred method is to put all the dimensions on model space and use a dimension style that is annotative. The benefit of this method is that I can see the dimensions while I am modifying the model and if I stretch the model to be longer I will stretch the dimensions at the same time so they always align with the model. Then when I go to paper space all I have to do is setup the viewports and hit print. However, due to the bugs that bricscad has with annotative multileaders I have to put all my multileaders on paperspace.
NOTE: The multleader bug we get a lot is that the landing length is not scaled properly so for drawings with a scale of 1:50 the landing length is made to be 50 times longer than it should be. And also, we have another bug that occurs occasionally when we switch to paperspace and then double click in a viewport. Bricscad does something that completely stuffs up the scaling of all the mutlileaders in the drawing so the text becomes 50 times bigger than it should be and the arrangement is completely stuffed up too.
So, based on these bugs we have to put all multi leaders on paper space. This is not our preferred option because we do quite a few drawings for a fleet of aircraft that are 90% the same but have slight differences and it is easier to see and manage those differences by putting multileaders on paperspace . All the common detail is on one layer. And we then setup separate layers for the differences. Then we can setup one sheet in paperspace for each aircraft. Make sure the viewports are in exactly the same position on each sheet and turn the appropriate layers on or off for each sheet. Then when you print to pdf and quickly flick between pages the differences stand out and are easy to identify because all the common information is in exactly the same spot on each page and your eyes notice the small changes more easily.
For 3D models, arranging dimensions in model space can be a bit difficult because you have to also manage appropriate UCS for all the different views that you ultimately want to setup in paperspace and put the dimensions at different orientations. The other problem with dimensions in model space is if you ever want to use that part/model as an xref in an assembly drawing. In that case you don't want all the dimensions to clutter up the assembly drawing.
So for solid models I will generally put the dimensions in paperspace. The downside with this approach is that the dimensions do not always work correctly.
Problem 1: If you have generated some views using the menu item View>Drawing Views>Generated Drawing Views BricsCAD has set them up to be clever. i.e. if you make a model of a cube and then generate views, then modify the cube to stretch one face so it is a longer rectangular prism, then BricsCAD will update the views to still show your complete model. But the dimensions on paperspace will not automatically update to match the model. There is a way to lock the generated views so they don't automatically update. But the down side of that is that you need it to update after changing your model. We had this problem with a model we created the other day and after making a very small change we went back to paperspace and all the dimensions were completely screwed up. We fixed up the dimensions and switched to model space, then back to paperspace without making any changes and bricscad updated the generated views again, the model moved again, and all the dimensions got completely screwed up again. So we manually made some viewports of the model and dimensioned that instead. The idea of generated views is nice, because they make it quick and easy to setup isometric projections of your model and they overcome a bug that AutoCAD always had with showing curves very badly. But they introduce some other bugs and we only use them when they are absolutely necessary. (p.s. we often want to copy a layout with the viewports and BricsCAD generated views don't work if they are copied. So for this reason we have to use the old style viewport)
Problem 2: If the viewport scale is not 1 : 1 (e.g. it is 1 : 2) you can create a dimension style that will recognise it is being applied to a mdoel and will scale the measurement to match the viewport scale. This only works when the dimension snaps to geometry of the model in the viewport. e.g. If I have a cube that is 1" x 1" x 1" and generate viewports that have a scale of 2 : 1 then dimensions you create in paperspace that snap to the model will all show 1" but if you measure them using the measure tool they will all be 2" long. That is all good and works as intended. But if I have a more complex model and many more dimensions then when I am creating dimensions some of the dimension grip points will snap to the model, but some will snap to objects in paperspace (e.g. snap to grip points of other dimensions). The dimensions that snap to objects in paperspace will not automatically scale. i.e. they will show a dimension of 2" and measure as 2" long (when you measure them in paperspace) but they appear to dimension an edge on the model that is actually 1" long in model space.
So this is an obvious risk when using this method and means we have to be much more careful when checking drawings before sending them to production.
So I would appreciate any thoughts from other users on how you work with these issues in your models.
Thanks/regards,
Denis Bowden
Comments
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NOTE: The multleader bug we get a lot is that the landing length is not scaled properly so for drawings with a scale of 1:50 the landing length is made to be 50 times longer than it should be. And also, we have another bug that occurs occasionally when we switch to paperspace and then double click in a viewport. Bricscad does something that completely stuffs up the scaling of all the mutlileaders in the drawing so the text becomes 50 times bigger than it should be and the arrangement is completely stuffed up too.
You don't state which version of BricsCAD you are using. There were issues like this with earlier versions of BricsCAD, but these have been fixed. If your using the latest release of V16, then you should raise a support request, including sample files. If you're on an older release and you aren't in a position to upgrade, then you should check you have the newest release for that version.
Regards,Jason Bourhill
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Problem 1: If you have generated some views using the menu item View>Drawing Views>Generated Drawing Views BricsCAD has set them up to be clever. i.e. if you make a model of a cube and then generate views, then modify the cube to stretch one face so it is a longer rectangular prism, then BricsCAD will update the views to still show your complete model. But the dimensions on paperspace will not automatically update to match the model. There is a way to lock the generated views so they don't automatically update. But the down side of that is that you need it to update after changing your model. We had this problem with a model we created the other day and after making a very small change we went back to paperspace and all the dimensions were completely screwed up. We fixed up the dimensions and switched to model space, then back to paperspace without making any changes and bricscad updated the generated views again, the model moved again, and all the dimensions got completely screwed up again. So we manually made some viewports of the model and dimensioned that instead. The idea of generated views is nice, because they make it quick and easy to setup isometric projections of your model and they overcome a bug that AutoCAD always had with showing curves very badly. But they introduce some other bugs and we only use them when they are absolutely necessary. (p.s. we often want to copy a layout with the viewports and BricsCAD generated views don't work if they are copied. So for this reason we have to use the old style viewport)
Generated views really need some work for them to be viable. If you're using BricsCAD Platinum, then BIMSECTION is currently a lot better in my opinion, and uses an approach which is more natural/familiar to the existing user. It also provides a great deal of flexibility in how you apply i.e. it provides you with a lot more control. Alternatives are to use FLATSHOT and LIVESECTIONS, which can be used to generate 2D geometry.
Regards,Jason Bourhill
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Problem 2: If the viewport scale is not 1 : 1 (e.g. it is 1 : 2) you can create a dimension style that will recognise it is being applied to a mdoel and will scale the measurement to match the viewport scale. This only works when the dimension snaps to geometry of the model in the viewport. e.g. If I have a cube that is 1" x 1" x 1" and generate viewports that have a scale of 2 : 1 then dimensions you create in paperspace that snap to the model will all show 1" but if you measure them using the measure tool they will all be 2" long. That is all good and works as intended. But if I have a more complex model and many more dimensions then when I am creating dimensions some of the dimension grip points will snap to the model, but some will snap to objects in paperspace (e.g. snap to grip points of other dimensions). The dimensions that snap to objects in paperspace will not automatically scale. i.e. they will show a dimension of 2" and measure as 2" long (when you measure them in paperspace) but they appear to dimension an edge on the model that is actually 1" long in model space.
I would check you Entity snap options (OSOPTIONS) in SETTINGS. Make sure that bit 4 is checked so 'Entity snap ignores end points of dimension extension lines'.
Regards,Jason Bourhill
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Thanks for the comments Jason.
I have the latest version running. I subscribe and generally always install the latest copy of Bricscad and have a support request with Bricsys for the mutlileader bugs that has been open since version 15.
I had a play with BIMsection but for the jobs we do I prefer to minimise the number of files and just work with 1 CAD file.
I know about the o-snap options and change them a lot depending on what I am doing with a drawing. I thought the best way to avoid the bug would be to hit F3 (to turn osnap off) but leave 3D entity snaps turned on. But that doesn't snap to end-points. I used the vertex snap but had some odd behaviour and that leads onto my next point/bug below. So it is just a matter of being careful with the snap settings and being very aware of which entity BricsCAD is snapping to.
I just discovered another odd but related bug today while testing some basic models to compile this discussion topic.
I have attached a picture to show the bug in action. I created a cube in model space (2" x 2" x 2"). Then created a viewport in paperspace for dimensioning. The LH side of the picture is a screenshot of the dimension after I have locked onto the top corners of the cube but have not yet selected a position for the text. The RH picture is immediately after I have selected the text position. You can see that the RH extension line has suddenly moved.
Then for the dimension I use o'snap to select the top/LH corner, followed by the top/RH corner everything looks fine. Then I position the dimension text where I want it to sit on paperspace and click that point. After that the second point I selected automatically jumps to the bottom/RH corner of the cube. So the clever dimensions have a few odd bugs in them and that make dimensioning in paper space very difficult.
For the second picture I went back into model space and used the solid extrude command on 2 faces. Then switched back to paperspace and my dimensions had automatically updated to suit the revised model. But the corners they were locked to had changed and the position of them had moved.
For the 3rd picture I put a dimension ont he side of the cube. Then went back to model space again and used solid extrude to move 1 face by 0.1 units. Then when I switched back to paperspace the dimensions had automatically updated to nonsense.
Given the nature of some of these bugs I am very surprise that I haven't seen more discussion on it in the forum. And that is why I am interested to know how some other people are using the programme to avoid these problems.
dimensioning in paperspace.jpg
dimensioning in paperspace 3.jpg
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@Denis Bowden:So for solid models I will generally put the dimensions in paperspace. The downside with this approach is that the dimensions do not always work correctly.To me, the possibility that a dimension in paper space will show an incorrect value is too big a risk. So, I have mostly stopped putting dimensions in paper-space. I have a macro that will freeze any layer that has the words "DIM" in them. But, yes it is a BIG mess when I do assemblies using X-refs.In another thread our BricsCAD Guru, Roy Klein Gebbinck, wrote a lisp routine to automatically identify any un-associated paper space dimensions. Here is the thread on that;-Joe0
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This question relates to modelling philosophy for dimensioning and annotating drawings. I am interested in the methods different people use to work with paperspace layouts, dimensions and mutlileaders to see if there are more effective ways to use them.
Generally when I am drawing 2D models my preferred method is to put all the dimensions in model space and use a dimension style that is annotative. The benefit of this method is that I can see the dimensions while I am modifying the model and if I stretch the model to be longer I will stretch the dimensions at the same time so they always align with the model. Then when I go to paper space all I have to do is setup the viewports and hit print. However, due to the bugs that bricscad has with annotative multileaders I have to put all my multileaders on paperspace.
I keep all dimensions, notes, and leaders in model space. My drawings are always 2D and entirely in modelspace. My layout tabs have nothing but a title block and some viewports. I don't use multileaders or anything involving the word "annotative."
After blocking out the geometry, I create a viewport in a layout tab just to confirm what scale the drawing should be printed at, and then I treat the geometry in modelspace as a drawing at that scale, just as I did in the days of hand drafting.
I use one dimension style and one text style. The only thing I have to do to manage scale is set the dimscale and text height to fit the scale the drawing will be printed at. For that purpose, I keep a pull-down menu (see image) that sets viewport scales and also serves as a reminder of the dimscale factor and text height that works for each of the ridiculous set of drawing scales that we imperialists use. That's a replacement for the 3x5 file card that early autocad users kept taped to our monitors.
But I have a dwg file that has a dimension, note, leader, dimension, reference arrow, title, north arrow, and graphic scale for each of the imperialist scales; so actually I rarely have to set dimscale or text height. Once the scale of the drawing has been determined, I copy the appropriate set of dimensions, leaders, etc in from that samples file and then copy them around the drawing.
If I create a new dimension or text entity, or borrow them from a drawing that was done at a different scale, I use the matchprop command, reversed in a custom version so that the target entities can be pre-selected and only the source entity needs to be selected at runtime, and I have custom commands that filter a selection set for dimensions/leaders or text/mtext.
I also scale linetypes so they can be seen in modelspace, and so I set Psltscale=Off in all viewports in my template file.
In short, I work in modelspace in WYSIWYG mode and without thinking about cad technology. I have enough building technology and code issues to occupy that side of my brain.
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Even dimensioning in model space is very buggy.
Refer to the attached picture.
I can select 2 very well defined points (e.g. I have snapped to endpoints to select vertices) and the dimension looks fine until I try to select the text location. The picture on the Left side shows the dimension just before I try to place the text. The picture on the right side is the same dimension immediately after I have selected a location for the text. The dimension text jumps to a different position from what I selected and also changes what it is measuring. For this very simple model I have tried to setup a dimension for one of the 1" lengths and had 6 different outcomes occur. Including the following:-
- 1 node jumps to a totally different location and it ends up measuring a totally different length (shown in the picture)
- One of the nodes jumps to the same location as the other node so I get a 0" measurement
- Both nodes jump to a totally different point from what I selected. But they both go to the same point so I get a 0" dimension again.
- 1 node jumps to the opposite end of the model. So it gives the right measurement but 1 extension line of the dimension overlaps the model
- The text position is put somewhere different to where I clicked
- Lastly (and most rarely of all the options) it does the right thing.
I have also tried it with annotative and non-annotative dimension styles and get the same results.
You have to be very careful to make sure the dimensions are actually showing the right information and on a more complex model (or a drawing done by a junior staff) it would be very likely that you have dimensions that appear correct but show the wrong information.
There are a lot of things I like about bricsCAD but these bugs make dimensioning of a model very, very difficult. Dimensioning in paperspace has a lot of fundamental bugs that make it too risky to use, but dimensioning in model space has different bugs that are equally problematic/risky. These bugs have been in the system for a long time and they almost make the programme unusable for generating drawings of solid models. If I was doing solid modelling more often I would seriously consider switching back to AutoCAD.
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I have done a lot of 3D modeling and dimensioning in model space, up to version 14, and have never seen the behavior you have described.The closest I have seen is if there is an associative dimension on a line that later gets filleted. Or even one associated with a segment of a polyline. Then, as the polyline gets edited, I can see behavior where the nodes merge. This is not a bug, but rather the normal AutoCAD behavior for those types of entities. So, to prevent this sort of unpredictable behavior, I have turned off the option to create associative dimensions. Then, all my dimensions are rock-solid.The only bug I have with v14 is that if I attempt to edit the text by double-clicking in it, my text goes giant, and becomes hard to edit. But, clicking outside of it, restores it. So I use the properties box to edit text.-Joe0
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After discussing this with Damian Harkin (Bricscad) we confirmed it was a bug and something in my template was causing it. I created a new template from scratch and it didn't have the same bug. So we have stopped the problem from occurring but have not yet identified what was causing it in the first place.
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