Thursday, September 27, 2012

Revit Work-Sharing File Protocol

Recently I attended a user group meeting that included a presentation on Revit Work Sharing and Worksets. Eventually three different users spoke about their procedures regarding central and local files, and all of them were different from mine.

Revit Worksharing was introduced in version 4 (2002?) and represented the first true multi-user BIM environment. With this innovation, all objects in the model were assigned to a collection; the "workset", which was required to be checked out by a single user. Conflicts still arose when an objects in different Worksets interacted with each other. These limitations eventually led to the development in version 6 (2004) of "element level borrowing", which lessened the need for Worksets, except on larger projects.

When Worksharing is activated, the single user file is automatically converted to a central file. Copies of the new central file are automatically designated as "local' files which must be periodically synchronized with the Central.

When this feature was initially implemented, all file management was manual. It was not unusual for inexperienced users to accidentally open the central file; one solution was to include the word 'central' in the file name, as a reminder.

Another common problem was the failure to save local changes back to the main file, locking other users out. This led to the so-called "best practice" of creating a new local file every day or even with each new work session. These protocols were originally all manual, and some users created external programs to automate the process.

Starting with version 2010 enhancements were added to make central and local file management more transparent. The Recent Files start-up window and the Recent Documents panel make it easy for users to select the correct file.

Now when users browse to a central file in Revit, the default result is automatic creation of a new local, in the location specified in Revit options dialog. The Revit user name is automatically appended to the central file name, which identifies it as a local file.

Some CAD users have developed the habit of browsing to a file and "double-clicking" it in Windows Explorer (which is fine for single user files). When users open a Revit central file by this method, or any other, they will soon receive a warning to save their work into a new local file.

As with CAD, when using Revit there is no reason maintain some strange attachment to procedures that have become obsolete. The Zen of Revit means developing a sense of "what Revit wants" and following it.

Sunday, September 16, 2012

“Core Only” Walls in Revit

Before the advent of CAD, on construction drawings walls were represented by two lines - which everyone understood to represent the wall’s entire thickness. The actual wall assembly was defined by details. The construction layers and finish materials of walls were always shown in larger scale views.

Then as now the standard for dimensions was to reference the face or edge or the core construction, because it must be placed first in the field.  General notes disclaimed “All dimensions are to face of structure unless noted otherwise”. When more specific direction was required, the letters ‘FOS’ or ‘FOW’ were placed next to the dimension line to denote the reference.

At one-eighth inch scale the size of a six inch wall is 1/16”, which is about as fine as can be drafted with pencil on vellum. In manual drafting, at smaller scales the same wall would be drawn thicker, by necessity. The level of detail was variable, depending on the scale of the drawing.

With CAD came the ability to add more detail and precision to drawings. Unfortunately, CAD did not have the human ability to automatically adapt drawing detail level to drawing scale, and management of this information by drawing layers (over hundreds of individual files) although possible, was eventually abandoned because it was impossible to maintain.

So it was all or nothing, and the practice of representing only the structural core of walls, and excluding finishes, evolved into the defacto standard for CAD.

The transition from manual production to CAD did not really resolve its problems; it simply exchanged old limitations for new ones. This compromise is one example of how the limitations of CAD were first accepted and are still perceived as obstacles to overcome in the transition from CAD to BIM.

Among the unintended side effects of this practice, with CAD room and building areas are often calculated by tracing a polyline around the perimeter of a space, not at its finish but at the wall core. Cabinetry and casework is often depicted as if the wall finish does not exist. These errors are not significant, but should hardly be defended when a better solution is presented.

Those familiar with its early history know that Revit was designed specifically to resolve the problems inherent in CAD. Revit allows dimensions to be referenced to structural elements, while also displaying the full thickness of the wall, finish to finish. Revit  also allows walls to be depicted with only two lines (coarse view) with unlimited options for color, fill pattern, and lines weight.

In Revit room areas are automatically calculated, with boundaries established at the user's preference. 

In addition, Revit area plans automatically apply rule-based algorithms for its calculations.

My advice to Revit users is to resist all temptation to use Revit to emulate the limitations found in CAD. Allow what is clearly obsolete to stay in the past where in belongs.