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Drawing comparisons

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Two new software packages both offer approaches to single building modelling but in quite different ways

For construction documentation, the two-dimensional drawing is king, cheap to duplicate and ultra-portable. However, during the development of designs, a three-dimensional environment provides more feedback to the designer about the form of the structure, the spaces being created and the effect of light within the space.

Developing a design in two different environments can lead to design discontinuity. Realising this, some smart cookies developed a solution which combines the 2D and 3D environments in one. This enables the designer to develop the design in 3D while simultaneously being able to extract 2D drawings in the form of 'cut'plans, sections and elevations. When the design is amended and the model is changed, the 2D drawings are updated automatically to reflect the changes.

This kind of innovative modelling is not new. RUCAPS and Sonata were jumping through similar hoops 10 to 15 years ago, but it is much, much more affordable now.

This reduction in cost is due, in part, to more powerful and affordable hardware and it has brought the single building model within reach. Along with the more established developers, some new boys are responding to the wind of change.

Two such newcomers to the UKmarket are Nemetschek, the grandfather of Germany's AEC software industry, with 'AllPlan FT'; and the fresh-faced Revit Technology Corporation with 'Revit'. The two companies come from very different backgrounds, but offer similar solutions to the market.

The companies Nemetschek is widely respected across Europe, with many thousands of bums on seats in the AEC industry. AllPlan FT sports a suite of discipline-specific products for architecture, engineering, landscaping, planning and finite-element analysis.

Conversely, the Revit Technology Corporation is new to Europe and was only launched in the US in May this year. Developed specifically for the architectural market, Revit does not contain tools for other disciplines such as HVAC or structural design. Although it has few users so far, the numbers are growing, due in part to Revit's 'early-adopter'programme, which offers discounts to a select few whose names will market well.

The interface Just as you should not judge a book by its cover, a pretty interface does not immediately mean you have a top-quality tool in your hands. However, the interface is your window into the heart of the application, and the simpler the layout of the tools, the more intuitive the application will be to use.

Inside AllPlan, the interface is refreshingly simple and is divided into disciplinespecific modules. The architectural module, for example, has walls, stairs, columns and roofs and so on. Clicking on a tool set loads the relevant icons in the main menu at the top of the screen. The working area therefore remains clutter-free. As you would expect from a Windows application, the toolbars are fully customizable.

Revit's interface works in a similar way. The discipline-specific tools in AllPlan are swapped for workflow-related tools in Revit. Again, screen real estate is maximised by having the same context-sensitive menus in the main menu but, unlike AllPlan, Revit does not currently enable users to customise the toolbars.

This would not have been such an issue had I not used my trusty laptop to review the software. Limited to a maximum screen resolution of 800 x 600, I was unable to access all of the allegedly 'available' tools.

Revit requires a minimum screen resolution of 1024 x 768.

The design process Before we look at how the models are structured and how they perform, we must first remind ourselves of the motivation behind the single building model approach. This is to erase the discontinuity associated with working in multiple environments, to develop, store and coordinate all of the project information in the same integrated environment. AllPlan and Revit, but they approach and tackle these issues in quite different ways.

Data structure The entire AllPlan suite is project-based, which means that any drawing or design, however simple, has to be assigned to a project. Each project consists of thousands of drawing files containing building elements such as walls, stairs and columns all of which are stored in individual files. Each individual file can be grouped within a file-set, such as floor, building or discipline.

Access rights can be assigned to individual files or complete file-sets to restrict unauthorised access to other people's data. In theory the entire project team can contribute to the single building model at the same time.

Revit is model-based and does everything within a single file. Created at the start of a project, the file swells in line with the complexity of the geometry and extended information attached.

This single-file approach has pros and cons. But it is easy to start using Revit early on in the feasibility stage of design without having too many constraints imposed. On the other hand, as the file gets bigger, electronic distribution across the web or by e-mail is onerous, as the entire model has to be transferred each time a change is made. Bandwidth remains expensive in the UK and, until it becomes faster and cheaper, this will remain a problem.

Operation AllPlan and Revit also differ in operation. Building a model in AllPlan is predominantly a 2D process, with the majority of design work carried out on the building's plan. Whereas in Revit, although working in the plan view is the norm, it is easy to work in any view at any time. This makes the process of 3D designing far richer.

When working in three dimensions, the plan view is not a flat plane like a piece of paper, merely a view on the top of the geometry. Therefore, data placed in the plan view must be placed on the right level, that is ground floor level, first floor level etc. Some applications deal with this by setting imaginary reference planes for data placement. Both AllPlan and Revit use actual reference planes, which determine where a storey starts and stops. All walls placed on the ground floor, for example, will extend upwards to the next level, the first floor or roof. Should the level they are reaching out to change, then all of the walls will change too maintaining the relationship created. At first I found this process a little tiresome but after getting to grips with it I found it a real advantage when developing and modifying a design.

In a similar way to the way the reference planes work, construction elements in each system 'talk' to adjoining elements and change their behaviour accordingly. For example, a window placed in a wall will automatically cut a hole in the wall for itself during placement.

Furthermore, if the window is moved and/or deleted, the hole in the wall will move and heal accordingly. This kind of conversation between geometric elements is often described as inheritance, where one element inherits certain information from its neighbour and changes its behaviour accordingly. In the same way all walls will trim to neighbouring walls.

Rendering Many commentators extol the virtues of the single building model approach to coordinating the entire drawing package while getting reasonable visuals from the model. Others rave about how their design and visualisation tool also produces drawings to construction-level quality.

In the case of AllPlan and Revit, it is the former group who will be satisfied by the rendering abilities of each application. I do not think anyone would select these tools to replace 3D Studio Viz in their architectural workflow, as the quality of the rendered output falls way short.

Drawing extraction Returning to the philosophy behind the single building model - to improve coordination between construction documentation - the product of the 3D model must surely be fully coordinated drawings. While AllPlan is competent in this area, Revit excels in providing the easiest way I have ever come across for compiling drawings from a model.

Views from the model are dragged and dropped onto a predefined drawing sheet. They can be placed at any scale, have any amount of hatching detail to suit the scale and they can be in rendered, hidden-line or wire-frame mode. Furthermore, the views on the drawing sheet can be edited and the model is updated along with all related views. Working in this way Revit will simplify the transition of moving from drawing in 2D to modelling in 3D.

Revit has also tackled the perennial 3D problem of cutting sections through models and seeing construction-ready details with great maturity. In Revit, 2D details can be inserted into the sections cut from the model and locked to key points of the section. For example, where a door is placed in the model and the section view is active, a jamb detail (like a block in AutoCAD or a cell in MicroStation) can be constrained to the location of the door. So that if the 3D door is moved in the model, then the 2D detail moves with it.

Import/export Unfortunately, in the real world people rarely all use the same application, and data exchange can wreak havoc. Both AllPlan and Revit claim to be compatible with all major formats (that must include AutoCAD's DWG). I did not manage to test each application's import and export ability and so I cannot confirm or deny the claims.

Conclusion While AllPlan and Revit are philosophically similar - they both support the single building model concept - they are in practice quite different. To start with, the companies are so different.

The interfaces function similarly but vary radically in quality.

The data structure of each could not be more different. AllPlan breaks each element type down into different files whereas Revit stores all the information in a single file.

When extracting drawings from the model the honours are split. For rendering images AllPlan leads the way from Revit's Accurender technology, but drawing extraction from Revit is about as good as it can get.

Perhaps it was naive to pitch two products together which are so clearly different, but they do both purport to answer the same question. I think though that the answer is in the maturity of the products. AllPlan FT is on version 16 while Revit is on version 2. With new releases promised every 100 days, Revit will be on a similar version by 2006. By then the balance should alter dramatically.

Joe Croser is a director with Adrem-DCX, a specialist in CAD consultancy and training. To contact him tel 07973 263360, e-mail Joec@adrem-dcx.com or visit www.adrem-dcx.com

Allplan FT

PROS: Established product, interface, good multiuser access

CONS: Small user base in UK (difficult to find experienced users)

Revit

PROS: Fresh new product, integration, one to watch

CONS:Large model files, no multi-discipline tools, no user base

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