This Client Server article is republished in its entirety from 2002 for reference purposes.
By Bentley Technical Support Group21 October 2002
Have you ever received the status-bar error message reading "Unable to modify solid" while working on a MicroStation V8 solid? Or, have you ever been unable to place a TriForma Linear Form in a file, or ended up with forms that you couldn't modify? If so, the chances are good that your solid is a SmartSolid located outside of MicroStation V8's Solids Working Area.
While MicroStation V8's method for storing coordinate data has made MicroStation/J's Design Cube a thing of the past for all practical purposes, the Parasolid modeling kernel built into MicroStation does require coordinate data at a fixed precision.
To guarantee that this precision is available, MicroStation V8 currently uses the Solids Working Area. This provides a way to quantify the maximum size of a Parasolid (SmartSolid) element, measured against the maximum possible precision for details (blends for example) on the element. To use MicroStation/J terminology, the Solids Working Area can be thought of as being a Parasolid design cube within the MicroStation V8 design environment, in which all 3D modeling involving the Parasolid modeling kernel should take place.
The size of the Solids Working Area is based on a file's working units, and can thus vary from file to file. To see how large it is, go to Settings > Design File > Working Units using MicroStation's pull-down menu, and click the Advanced button. In a metric file, the value found in the Working Areas > Solids field is the length-in kilometers-of one edge of the Solids Working Area. Thus, a cube centered on the center of the design file whose edges have this length is the Solids Working Area (See Figure 1).
Figure 1. The Advanced Working Units dialog.
A useful tool called SWA.ma places a graphical representation of the Solids Working Area in the design file as either a graphical or transient element. Simply download the file, unzip the swa.ma application to your Bentley\Program\MicroStation\mdlapps\folder, and key in ‘mdl load swa.' This places a transient element in your model. Closing the file, or keying in ‘mdl unload swa' removes the transient element.
The value in the Resolution field of the Advanced Unit Settings dialog box determines the size of the design environment, as well as the size and accuracy of the Solids Working Area. Note that changing the Resolution setting will change the size of elements in the design file, and could cause compatibility issues when saving to MicroStation v7's file format. MicroStation provides a pop-up window to remind you of this when opening the Advanced Unit Settings dialog box (See Figure 2). As mentioned in MicroStation V8's Help system, the maximum accuracy for solids can be achieved by setting the Resolution to 1,000,000 per meter, and setting Solids to 100 kilometers.
Figure 2. The Advanced Working Units alert dialog
With a given resolution, changing the value in the Solids field will change the size of the Solids Working Area, which has an inverse relationship with the solids accuracy; the larger the Solids Working Area, the lower the Parasolid accuracy, and the greater the chance that you might see problems when the Parasolid kernel's calculations require extreme accuracy. Note that changing the size of the Solids Working Area does not change the size of elements in the file.
One mistake some users have made in the past is to change the Master Unit Label in the Working Units section of the Design File Settings dialog box, without changing the Master Unit itself. MicroStation ‘thinks' in master units, but allows you to choose your own label, which shows up in MicroStation's user interface. Thus, if you want to change your working units from meters to millimeters, but only change the Master Unit Label from "m" to "mm," MicroStation will continue to draw in meters. However, it will display all measurements using the label "mm" (See Figure 3). If you then place a wall, which you think is 7000mm long, in reality it will be 7000m long, most likely extending out of the Solids Working Area!
In some situations SmartSolids can exist that appear to be inside the Solids Working Area, but are actually outside of it. This can occur when geometry is copied between files with different Solids Working Areas, or when the Solids Working Area is changed and SmartSolids are moved, both of which cause an additional scaling factor to be applied to the SmartSolids boundary representation data. These situations can be avoided by using the same Solids Working Areas in your reference files and master files, and by avoiding drastic changes to the Solids Working Area while modeling.
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