Recommended Working Units

From the Settings>Design File>Working Units pull down menu of any design file in the Resolution category of the Advanced Unit Settings for working units, it is important to note that Positional Units are used as a count to make one sub unit and that the Positional Unit or Resolution represents the smallest possible distance available in MicroStation.  For a metric design file example, a resolution value of 10 could be used, and that would mean that there would be 10 Positional Units in one millimeter, thus allowing us to draw down to only 1/10th of a mm. The lower the Resolution value, the less fine or detailed the model will be, but it also results in a larger Solids Working Area in which to build.  If you were to increase the Resolution to 1000, then you would have a more detailed and accurate model, but a smaller Solids Working Area.

The Working Area category reports how large of an area we have to work with in master units. One of the biggest working units change since MicroStation V8 is the Solids Working Area.  This is what used to be the entire Working Area in V7 and earlier, but is now where all Parasolid operations are performed. Solids and Surfaces can exist outside the SWA, unlike older versions, but are transformed to the SWA if they require Parasolid interaction of any kind – modeling, editing, drawing extraction, etc. This is the reason it is typically suggested to use Bentley’s delivered working unit Resolution since that’s what is used for development and testing.

Potential problems associated with using a smaller Resolution value includes incorrect or missing elements in drawing extractions and walls or elements that are not joined together in the 3D model. This can be verified by zooming into the element as far as possible to view the connections. Bentley Building’s recommendation would be to use the Resolution value we provide in our delivered metric seed files – 1000 per mm. That’s a factor of 100 when compared to using 10 per mm Resolution, which would be considered a low value.

A few other things to keep in mind...one is regarding Resolution vs. the size of the Solids Working Area. Unless you are modeling something larger than 4.29 km, which is the delivered metric Solids Working Area, there should not be any need for a larger SWA. If real-world coordinates are a factor, you can shift the Global Origin to compensate or use Geo-coordinates.  Another important factor is to be sure to keep the same Working Units for all files within the same project.  Otherwise, you may find wrong sizes, measurements and placement of reference files that coincide in the model. 

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