CADD Engineering Standards - Ohio Department of Transportation

202.5 Priority and Transparency
January 18, 2013
The levels defined in the MicroStation DGN Library, ODOT_Levels.dgnlib, utilize the Element Priority
and Transparency features. The Priority and some Transparency settings have been incorporated in
ODOT CADD Standards to facilitate the on-screen viewing of the plan features. See the CADD
Information Table Appendix A, for a complete list of Priority and Transparency values.
Priority
• Priority
Elements, levels, and references can be assigned a Priority value. Elements with a higher priority
will display on top of elements with a lower value.
• Transparency
Dialog boxes, as well as elements, levels, and references can be set with a transparency value.
Transparent elements allow you to see other graphic elements that are “underneath” a
transparent element.
Display priority is a technique for specifying the relative front-to-back order in which 2D elements appear
in a 2D model (only) when they are displayed in a view. Display priority is only useful or necessary for 2D
models, since all elements in 3D models have their own explicit 3D coordinate space. In 3D models,
elements closer to the eye are always drawn in front of elements further from the eye so display priority is
not necessary.
The elements with the highest priority values are displayed in front, while the elements with the lowest
priority values are displayed in the back. Values for Element and Level priority may range from -500 to
500.
By default, MicroStation displays the elements on your screen in the order in which they were drawn. If
you're using reference files, the active file will display first followed by the reference files in the order of
attachment. And finally, if you're using raster reference files, the order is: the raster images first, then the
active file elements, followed by the vector reference files.
Note: Levels for Raster Reference files have been created. The Raster Reference files have
been assigned a low priority value so they will always be displayed behind any existing and
proposed features and references.
ODOT CADD Engineering Standards 11