Building Bridges - A commentary on V4 to V5 functionality
 
 
Layering existed in prior CATIA releases to handle a variety of needs. Very early on (CATIA V2), it was necessary to place multiple assembly components into a single CATIA model and Layers and Filters were used to manage the display of these components. Solid modeling was not used extensively in earlier versions of CATIA; therefore, Layers and Filters were needed to manage the display of pieces such as wireframe, surfaces, faces and volume describing a single part. Because multi-model links did not exist, it was necessary to store downstream applications such as NC data in the same model, and Layers and Filters made this manageable.

Rather than further elaborate on Layer usage in V4, let us stop here and think about Version 5. Hide/Show is an easy concept for the V4 user to grasp. Yes, in V4 there is No Show/Show function along with Layers, but let us consider this more closely. When solid primitives are selected for modification in V4, their profile geometries automatically become visible, even when stored in No Show. When the change is complete, the geometry returns to its hidden state. It is interesting to note how many companies do not allow any geometry to be stored in No Show. This is generally because automated checking programs cannot distinguish elements that are linked to solids from unnecessary points or lines.

Some companies continue to place construction geometry on a separate layer (a V3 practice), when it clearly is not as efficient for the designer. This practice illustrates the reluctance of users to change established practices, but imagine the designer's dilemma if we had not changed from 2D to 3D. In V4, it is not possible to work in the No Show area or to alter geometry that is hidden. The V5 user may use Swap Visible Space to select and alter components. The "hidden" working area has a light green background that easily distinguishes it from the main working area. The result of this added V5 capability is two main working areas-all that is necessary when working in a single component (the solid model), using a single application (part design, assembly design, drafting, NC, etc.). The Specification Tree and Contextual Menu make it simple to bring elements (i.e., sketches and reference planes) in and out of Hide. When it comes to assemblies, it is not only unnecessary, but also inadvisable, to put multiple components together within a single file. Do we want to re-release an assembly each time a single part is changed? Do we want to leave the assembly released with obsolete components? The creation of assemblies that copy geometry, rather than reference it, is a data-management nightmare.

CATProduct references part data and also contains instructions for how these pieces relate to one another. (Assembly design is another good candidate for a separate article relating V4 and V5 differences.) Staying on our topic of Layers, within CATProduct it is possibleto hide entire parts or to hide (or make visible) individual sketches or references contained in the part. When various configurations of the same assembly are required for a drawing, technical illustration or other type of documents, the Scenes tool provides the flexibility that is similar to multiple Filters, and goes even further. In addition to storing visibility and color of components in multiple configurations, Scenes also can store a variety of positions, such as exploded or assembled. Scenes are stored in CATProduct, but are accessible for use in other documents, such as CATDrawings.

Finally, it is difficult to believe that anyone who has taught the use of Layers and Filters or has participated in the development of a standard layering convention will regret that this paradigm has been omitted from V5. The new tools are easier to learn, easier to use and more efficient.

SolidE Boolean operations still exist in V5, but only are used in specific cases. V5 uses a feature-based modeling approach and it is not necessary to subtract a hole, because the nature of such a feature is the removal of material. The tools in V5 inherently determine whether material is to be added or removed. It is possible to create separate Bodies and to Add, Remove and Intersect them with one another, but it is best to begin V5 with the feature-based idea, and leave V4 methods behind. These examples may help to explain why it would be a disservice to provide command-to-command translations. V5 is a natural transition because it utilizes the designer's feature-based thought process and is a truer reflection of real-world geometric relationships. However, it also is natural to resist change and to be apprehensive of the unknown. V5 is a new product and new practices must be learned.

 
© 2008 EDS Technologies.