If a Form does not respond correctly to a modification command, or any other command, there may have been an issue when user data was written for the Form. It can be “rebuilt” using the key-in TFREBUILD. This command deletes the selected Form and reconstructs the Form with the same parameters as the original. When a Form is “rebuilt”, user data has the correct format and the Form is usable again.
As is always the case when repairing any file, be sure to make a good backup copy.
In 3D models, click Edit-Select All (or use Control A or selectively choose what to rebuild) while in the file (and also in each of your 3D reference files), then key in TFREBUILD in the key-in browser, and click Yes when prompted. All selected components in the file will be "rebuilt" with the current software version's information. Or a single Form can be "rebuilt" by simply selecting it (you will be prompted) after the key-in is executed.
Back in the olden days Forms were referred to as having a built-in “recipe”, stored in plain text format to save disk space, that described how the element was to be handled and displayed. A TFREBUILD “re-runs” that Form’s recipe to resync its boundary representation (graphics) with its internally stored data. These excerpts from the original V8i readme describe a process introduced at that time to automatically “run” the recipe in pre-V8i files in order to natively store the Parasolid data instead of just the recipe:
…If a designer is using a pre-V8i (legacy) project in V8i or receives the following warning in the message center: Performance Tip - View update speed will be increased by adding view accelerators to Building elements. Use dvperformancebooster.exe on your legacy file(s).
Run the DV performance Booster utility found under Start>All Programs>Bentley Building V8i (SELECTseries #)>Building tools>DV Performance Booster> to upgrade the geometry within the project. This is a non-destructive process and should not cause issue with your file. It will result in a minor increase in the file size. A project created with V8i typically does not need to run the DV Performance Booster utility.
Pre-V8i legacy Forms store a recipe to recreate a Parasolid body but they do not store the Parasolid body by default. The recipe must run each time the body is displayed (on first draw, when no runtime caching has been performed). This is the classic trade-off between speed and space. DV Performance Booster utility forces the Form elements to store the body, sacrificing space for speed. Storing the body makes operations that need the Parasolid body (like unification) faster because they don't have to reconstitute the body (on first draw). This process is called hydration, or hydrating a file. A project created with V8i typically does not need to run the DV Performance Booster utility. Parasolid bodies are automatically stored by default in V8i, unless that v8i file has been dehydrated by running the dvperformancebooster.exe with the dehydrate option.
This is also directly related to “Delete Building Display Accelerators” in the Compress option dialog, Removing the Parasolid data reverts back to the recipe, exchanging performance for disk space. This is why the command only works in 3D since it’s dealing with Parasolid (3D) data.