Dimension Driven Design

Here’s a complete list of links to the DDD video collection for faster downloading:

00 Introduction
01 The Basics
02 Geometric Constraints – Part1
03 Geometric Constraints – Part 2
04 Geometric Constraints – Part 3
05 Degrees of freedom (DOF)
06 Symbology and Definition
07 Getting Help
08 Dimensional Constraints – Part 1
09 Dimensional Constraints – Part 2
10 Dimensional Constraints – Part 3
11 Algebraic Constraints – Part 1
12 Algebraic Constraints – Part 2
13 Attaching Graphics – Part 1
14 Attaching Graphics – Part 2
15 Automation – Part 1
16 Automation – Part 2
17 Automation – Part 3
18 Special Constructions
19 Dimension Driven Cells
20 Rounding – Part 1
21 Rounding – Part 2
22 Conditional Formatting – Part 1
23 Conditional Formatting – Part 2
24 Min and Max
25 Table Lookups – Part 1
26 Table Lookups – Part 2

here it is, if you’re looking for it…

This video follows on from Table Lookups Part 1 to complete the set and complete the whole series on Dimension Driven Design in Microstation.

If you have managed to stick with me the whole way through the series, congratulations! (I couldn’t have done it!)

Thanks for you’re company, and please, fell free to leave comments, questions, tips, suggestions, books on geometry, $100 cheques or contracts for jobs!

Take Care

~Colin

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This video demos a technique to simulate Table Lookups. At a stretch we could think of this as a simple if, then, else construct.

This is Microstation’s DDD at the limits of my knowledge, and it’s fun too! BUT is very very useful aswell. Don’t all Engineers love empirical formulae and Tables upon Tables of values when designing? Why not let Microstation look them up for you?

It is a combination of many behaviours and techniques described already, nothing new, just putting them together in a different way.

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More Math…

How to return either the minimum or maximum values by comparing the resutlts of two different expressions… again, I have found this unassuming little ability VERY important - DDD would be practically of very little use to me, if I couldn’t do this.

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Following on from the previous video, an example of Conditional Formatting Driving Graphics in the practical example.

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To present some Conditional Formatting in the DDD solution, another little bit of Math is employed. I prefer to use Conditional Formatting to give visual feedback during the design to let me know if I have exceeded design limits. But not to retrict me at the same time.

There is another (simpler) method, which will prevent or limit expressions from returning values outside of a specified range, shown in the video too.

This first video shows the theory behind Conditional Formatting, the next will demonstrate how to set it up with Graphics in a design file.

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This Video continues directly from the practical example started in Part 1.

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This video is about Rounding values that are retrieved from Expressions, similar to round, roundup, rounddown, ceiling, floor etc in Microsoft Excel. However, we only have a much much shorter list of options available to us in DDD – and even those are not documented as part of DDD.

So a little bit more manipulation is required, while this video (and the next few following) are not necessarliy about the tools in DDD, they are about some advanced methods we can use in with DDD in order to get even the most from it.

Another tip that gets thrown into the video (and I want indexed by Google…)

Don’t use the word processor to edit DDD expressions. For more reliable performance, if you are finding expressions won’t get applied to solutions properly, it may be that there is some unusual character encodng blocking it from getting processed, instead use the Dialog Box to place and edit text.

And this dull maths gets followed up by possible pratical example of where Rounding might become useful in real-world designs.

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Placing a DDD solution as a cell (using the DD Cell tool palette, keyin: DDCELL TOOL) opens up a few more functions to us.

It allows us to place the cell with or without constraints and designate each variables values before placing the cell graphics into the design file.

If we remeber from an earlier video, I mentioned that to Copy and DDD solution – use Microstation’s clipboard; alternatively you could create and place cells if that is more suitable.

Another item to note is that all DDD solutions are automatically assigned to a Graphic Group which can be useful when deleteing a cell from a collection of overlapping but independent DDD solutions.

In the video I also go through the other tools available from the DD Cell tool palette. One useful one is Drop Driving Dimension, although the normal technique here is simply delete the dimension, this option might get you out of a hole at some time.

Lastly there are a couple of tools in the DD Cell tool palette which don’t work for me, DD Cell Origin and Attach DD Cell, for unknown reasons.

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There are 3 types of Special Constructions in Microstation’s DDD toolbox:

• B-Splines
• Constrained B-Splines
• B-Spline Cells

B-Splines are like LOCKed elements (no degreees of freedom) and can have points Constrained ON them.

Constrained B-Splines can have their ‘knots’ constrained by other Constructions in order to change the shape of the B-Spline, but canNOT have points constrained ON.

B-Spline Cells CAN have points constrained ON, and can also have a directional constraint, tangental contraints and point (from its center), but canNOT have their ‘knots’ constrainted.

…watch the video and it all become clear

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The third video on Automation is a quick look at some of the ‘other and miscellaneous’ tools in the DDD toolboxes, some of which don’t always get a lot of mileage – but for the sake of completeness in this series described here as best I can:

• Break Constrained Geometry
• Trim Constrained Geometry
• Fillet Constrained Geometry
• Chamfer Constrained Geometry

Two little extras at the end of this video… they don’t really fit to well anywhere else but are quite important and used all the time.

The first is a look at Describe Constraint which is the little Microscope Icon (I think!) found on the Evaluate Constraints Tool Palette.

The second and most important describes how set or change the size of all Constraints widgets as drawn on screen by Microstation. Hint: Found under the Sketch Profile and Convert Element to Profile tools in the Set Text Size Automatically area.

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This video takes a deeper look at comaprisons between Automatic and Manual solution building with 3 different methods:

• Manual
• Convert to Profile (auto)
• Sketch Profile (auto)

This is also probably the first opportunity to see a ‘completed’ solution in that it includes all presentation graphics, constraints, driving dimensions and presentation dimensions amd an ‘anchor’. The solution also includes some Symmetry – which can only be added manually.

The result of this comparison demonstrates tht even on the simplest solution, Automatically placed constraints can number about 150% more than a solution that was built manually.

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Well, we’re just over halfway though the series on DDD, time flies!

If anyone would like to give feedback here at this point, please do! I don’t expect there are many people following along as matter of daily course, but nevertheless any questions or suggestions can only help to improve the quality of the materials I’m publishing here, and influence potential subjects for any future materials. Remember – there’s no such thing as a stupid question, and the questions don’t necessarily have to be 100% ‘on topic’.

Contact is welcomed either directly here or by email: colinlarkin@gmail.com

Right, back to the business at hand…

Automation is a very important and and sometimes very useful part of DDD. A good understaning of how it works is very beneficial to the solution builder.

This first part starts by comparing some sample steps taken for the manual method with the Automated method. Then I go further with a second example and compare how automated constraints can make less efficient choices than might be desired by the designer. Finally a quick look at the Constraints Tutor which is found in the Profile tool palette and includes the Convert to Constraint and Sketch Profile tools.

As I tend to repeat many times, I’m not a huge fan of Automation for real-world works in complex solutions. I would also recommend not becoming reliant on Automation, because if something goes wrong – a good understanding of the manual is needed for trouble-shooting and repair.

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Two videos today (to make up for missing yesterday!). The next subject is attaching graphics – the last piece of the puzzle when building a DDD solution.

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Download the following DGN file which includes a simple arc calculator to determine:

• The Radius of the Arc
• The Angle Subtended
• The Length of the Arc
• The Chord Length
• The Chord Height
• The Sector Area

Any Two Parameters must be known – and the rest will be returned real-tijme on-screen.

The Arc (solution) can be re-located using the Modify and Re-Solve Constraints Tool on the Right-Angled Arrow ‘Handles’.

 arc_calculator.dgn

Folowing up in this video with a couple of common and practical examples:

• Assigning a variable to multiple dimensions (to achieve equal divisions or symmetry)
• Constructing an arc that can be driven by length usings equations

And as a bonus, I make some errors in forgetting to make dimensions associative while placing, which might help with trouble-shooting.

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Unlocking the endless possibilities and power of DDD though the use of Algebraic Constraints, at the very least, standalone Algebraic constraints solutions can serve as saved calculations that might be repeatedly punched into your desktop calculator. In other cases it can replace those spreadsheets and give you direct access to complex calculations right in your design environment, saving window-switching multilple document management and tracking.

But the ultimate use is when assigning these outputs to Graphical Solutions for prototyping designs and generate final presentation output all in one shot.

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Looking at the various types of dimensions that can be assigned as constraints, which make up three main groups:

• Distance
• Radial
• Angular

Then describing a selection of the most suitable dimensioning tools for conversion to constraints.

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The second and third methods for adding Dimensional Constraints… converting dimensions to constraints and assigning variables to dimensions.

And a little info on variables, constants and naming conventions.

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This video is in response to a question I read on discussion.bentley.com, about how to adjust an arc to a specific length with Accudraw (not using DDD – cos that’d be too easy)

It’s an interesting use of Accudraw at least – did you know that Accudraw’s popup calculator can handle complex expressions, can save and take user-defined variables, one useful one which is already there: pi?

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Today’s video describes the first of three methods for adding dimensional constraints to a DDD solution, namely: Adding a Variable while placing a dimensonion

On a side note, another procedure was shown here: copying a DDD solution. It’s worth noticing that DDD solutions should be copied using the Clipboard as opposed to Microstation’s Copy Element Command. Go ahead, try both methods out and taste the difference!

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P.S. Apologies for the delay in posting yesterday’s video, I hadn’t noticed that I forgot to hit the ‘publish’ button, thanks to those of you keeping an eye on me though

As I have mentioned a couple of times already, explaining and understanding the abstract concepts, or the mental angle-of-attack assumed when preparing to work in DDD is fairly subjective. For the reader or viewer here to tune into my explanations may be easy for some and not-so-easy for others.

If you find anything dischordant so far, why not read about the DDD from another’s viewpoint? This video talks about a few different resources available (that I know of) and should be helpful if you get stuck on any point or need more clarity.

By the way, if anyone knows of any other resources that I have missed, please leave them in a comment below, thanks!

Tomorrow (and from here on out), we’ll get back into the meat of the subject.

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Here are hyperlinks to some of the resources mentioned in the video:

• http://discussion.bentley.com
• ftp://ftp.bentley.com/pub/help/tutorials/

Today’s video continues directly on from the previous discussion on Degrees of Freedom, and looks at how Microstation displays visual feedbask through element symbology as to the status or ‘definedness’ of your working solution.

The language of DDD is one of the biggest hurdles when developing and understanding of how to get the most out of it. It would probably cause more confusion by trying to ‘invent’ new, more meaningfull and less abstract terminology.

So instead, once again, I recommend to ‘learn by doing’. A little experimentation and a few ‘A-HA’ moments later and all the concepts of of Microstation’s implementation of DDD become very clear… from that point on it becomes plain sailing.

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All about understanding, adding, removing, testing and reporting degrees of freedom in a DDD solution.

From the Help File:

…ambiguity in a design is summed up by a number called “degrees of freedom.” Each new construction adds degrees of freedom as follows:

Construction	Degrees of Freedom Added
Point	2
Line	up to 4
Circle	up to 3
Ellipse	up to 5

Each valid constraint removes one or more degrees of freedom.

A well-constrained design has zero degrees of freedom and no redundant constraints. All constructions are well-constrained.

If the number of degrees of freedom is not zero, then parts of the design are under-constrained.

When a constraint is added, the remaining degrees of freedom are displayed, followed by the message “OVER-CONSTRAINED” if there are any redundant constraints.

And if all that sounds confusing, don’t worry it is! The best way to understand DOF is to get stuck in and experment with some simple tests.

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Two videos today, dealing with point geometric constaints including:

• Point-On
• 2 methods for using Point-At
• Coincident
• Equate

I’ve also described an important and very useful behaviour where a circle construction can be used to behave a point construction in the right circumstances.

Finally some opinion about avoiding using the Equate Constructions command as I have found it a touch buggy. While I neglected to provide examples of this, it still useful to be aware of when trouble-shooting a problematic solution.

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Today’s video describes the Constrain Elements toolbox, which is found under the first icon in the Geometric Constraints tool palette.

The tools found are conveniently grouped, as they create relationships for Lines and Ellipses only.

The first tool is ignored (for now), and the rest demonstrated quickly are:

• Tangent
• Perpendicular
• Parallel
• Direction

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In this, the first video proper, the foundation components of DDD are introduced; namely Constructions and Constraints.

If watching this video series in conjunction with other DDD documentation, note that there may be some slight variations in the terminology used. For example ‘constructions’ are referred as a constraint type in the MicroStation documentation, but are referred to seperatly here for clarity.

I had considered renaming ‘constructions’ to ‘elementary constraints’ for the purposes of these videos and to avoid confusion with construction class, but felt that – even though alternate naming might be more meaningful, it would probably be prohibitive to learning in thelong run.

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This first video Introduces the Parametric design concept in Microstation, demonstrates some examples, and discusses its suitabilty for integration into existing worflows and standards.

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A new video will be published every day for the next month (or so) here is a sneak-preview of titles as they will appear:

• 01 Introduction
• 02 Geometric Constraints – Part 1
• 03 Geometric Constraints – Part 2
• 04 Geometric Constraints – Part 3
• 05 Degrees of freedom (DOF)
• 06 Symbology and Definition
• 07 Getting Help
• 08 Dimensional Constraints – Part 1
• 09 Dimensional Constraints – Part 2
• 10 Dimensional Constraints – Part 3
• 11 Algerbraic Constraints – Part 1
• 12 Algerbraic Constraints – Part 2
• 13 Attaching Graphics – Part 1
• 14 Attaching Graphics – Part 2
• 15 Automation – Part 1
• 16 Automation – Part 2
• 17 Automation – Part 3
• 18 Special Constructions
• 19 Dimension Driven Cells
• 20 Rounding – Part 1
• 21 Rounding – Part 2
• 22 Conditional Formatting – Part 1
• 23 Conditional Formatting – Part 2
• 24 Min and Max
• 25 Table Lookups – Part 1
• 26 Table Lookups – Part 2