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  • ArchiCAD 15: Part 2
     
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    ArchiCAD 15: Part 1

    continued

    Many older examples were designed using paper and pencil alone, which had the advantage of being able to represent almost anything. Newer examples from the pre-BIM era were accomplished using CAD, which had the advantage of being able to draw freeform shapes but did not provide any assistance with the design process as such, since it did not carry any intelligence about the elements it was representing.

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    In contrast, BIM has the potential to be a full 3D design and documentation tool, but so far, it has been limited in its capability to enable architects to freely conceptualize and design buildings with non-traditional forms.

    BIM programs such as Revit have greatly improved their conceptual modeling tools in recent releases, but in most cases, the freeform capabilities can only be applied to the conceptual model, which is then used to generate the BIM model. Thus, any change to the form of the building has to be applied to the conceptual mass first and is then propagated to the BIM model, resulting in an interrupted, less-than-optimal workflow.

    Ideally, it should be possible to create freeform building shapes directly in the BIM model, so that any required change can be made directly to that model rather than to a separate conceptual model.

    It is precisely this that ArchiCAD 15 sets out to achieve, with a new Shell tool that allows freeform BIM elements to be created, a greatly expanded Roof tool, as well as interface enhancements that make 3D modeling, editing, and navigation easier and more accurate. Let's start by looking at the Shell tool.

    New Shell Tool for Freeform BIM Modeling

    The Shell tool is the main new freeform BIM tool introduced in ArchiCAD 15. It has three different geometry options, Extruded, Revolved, and Ruled, which allow you to model a wide variety of forms. Each option has both a simple construction method for creating a basic shell of that type quickly, and a more detailed construction method, which allows you to draw a more complex profile for creating the shell.

    The shell profiles can be created in any view and can also be edited graphically in any view to modify the resulting form. The recent 3D interface enhancements, which will be discussed in more detail in a later section, make it much easier to create and edit shell profiles in the 3D window.

    In addition, there are a large number of parameters that can be used to fine-tune the shell as required. Basic parameters include the shell thickness and the positioning of the shell body with respect to the defining membrane generated from its profiles. Additionally, there are three angles — starting, ending, and distortion — that can be used to change the orientation of the defining profiles and thereby dramatically alter the shell membrane and the resulting shell form.

    You can specify the material of the shell, which can also be a composite structure. The shell is correctly shown in plan, elevation, and section views, including all of its layers if it is made of a composite material.

    Once a shell has been created, you can easily create skylights or holes in it. Walls and 3D zones can be trimmed against the shell, and they maintain their associativity so that if the shell element is modified, the walls and 3D zones automatically adjust to the new shape.

    To ensure that the shell is a BIM object, it can be classified as a roof or slab element and thus remains true to the BIM nature of the model. This allows it to be exported to the IFC format for interoperability with other BIM applications. It can be scheduled just like any other element, with accurate calculation of geometric properties such as surface area, volume, etc. Its quantity takeoff is also accurate, even if it is a composite structure — all its individual materials are calculated accurately.

    Thus, as you can see, the new Shell tool supports the broadest spectrum of architectural shapes for building structures that are prevalent in both historic and modern architecture.

    These structures, when created in ArchiCAD 15, remain an organic part of the entire BIM workflow without the need for conversion at any stage of the process, following the basic premise of the application that conceptual design should begin directly in the BIM model and architects should not have to create a separate conceptual model. They should be able to start any design with BIM elements from the first click, and should be able to modify any element freely. Also, the freeform modeling capability supports the entire architectural workflow, ranging from concept design to design development to construction documentation, because there is no "concept" or "massing" model separate from the BIM model.

    While the new Shell tool is primarily intended for building modeling, it is flexible enough to be used for product modeling as well. However, generic 3D modeling applications do have a broader set of tools and interface features to support product design, so it is unlikely that ArchiCAD 15 would be used by product designers instead of these applications. But it will certainly help those architects already using it to venture beyond building design and use the application for modeling furniture and other interior design elements, if required.

    Revamped Roof Tool for Modeling Complex Roofs

    In ArchiCAD 15, the existing Roof tool has been completely overhauled to make it much easier to model complex roofs, which are still a significant architectural element in many building types. There is a new Multi-plane geometry method for roofs that can be used to create a complex roof — which includes multiple planes and several roof levels — as a single roof element.

    You can select the series of points that will form the base of the roof (which would typically be the outer corners of walls or the corners of a zone), or use the Magic Wand tool to select a closed set of walls or a 3D zone, which will "magically" create the roof. The Magic Wand can also be used to add additional portions to the complex roof, or cut holes in it for atriums and courtyards.

    The roof is created with the default settings, which can be modified in the Roof Settings dialog, such as the angle, pitch, eave offset, materials, number of edges in a curved roof, and so on. You can also edit the roof geometry interactively, using the large number of "pet palette" (contextual tool palette) options that are available when you click on an edge or a plane of the roof. The roof geometry can be changed as a whole or you can make changes to individual planes — for example, changing their pitch, making them a gable, changing their material, fill, or eaves overhang, and so on.

    Because the complex roof is created as a single element, it is fully associative, so that any change made to a point, edge, or plane propagates intelligently through the entire roof, maintaining its connections and configurations. Roofs can also be trimmed against each other, and any subsequent changes to them continue to maintain their connectivity.

    It should be noted that while walls and 3D zones can be trimmed against roofs, and roofs, in turn, are associative with each other, this associativity does not exist between walls/ zones and roofs. This means that a roof is not automatically reshaped when the walls or the zones used to derive it are modified. So if there is any change in the spatial configuration of the design, the roof will have to be manually modified — it can be generated from the floor plan but does not stay associated with it.

    Just as with shells, you can also add openings and skylights to roofs. In ArchiCAD 15, the Skylight tool has been enhanced to better support adding skylights to complex roofs and shells. They can be placed on flat as well as curved surfaces and appear accurately in floor plan representations by being true 3D vertical projections. They remain associated with their parent roof or shell, adjusting and reorienting themselves automatically when the geometry of that roof or shell changes.

    Discuss this article in the Architecture Forum...

    Lachmi Khemlani is the founder and editor of AECbytes, an online publication focused on researching, analyzing, and reviewing technology products and services for the building industry. She has a Ph.D. in architecture from the University of California, Berkeley, specializing in intelligent building modeling; a professional B.Arch. (honors) degree from the Indian Institute of Technology in Kharagpur, India; and an M.Phil. in architecture from the University of Cambridge. Khemlani has worked on design projects as a practicing architect, authored books on CAD and modeling, and taught CAD and 3D modeling at UC Berkeley. She currently consults and writes on AEC technology.

    This article is excerpted from "ArchiCAD 15" by Lachmi Khemlani, copyright © 2011, with permission of the publisher, AECbytes.

     

    AW

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    SUBSCRIPTION SAMPLE

    The third transformation supported by the Shell tool in ArchiCAD 15, called the Extrude operation, creates an object through the simple extrusion of a 2D outline.
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    SUBSCRIPTION SAMPLE

    In addition to adjusting the orientations of the original surfaces of a shell object, ArchiCAD also offers control of the relative distortion angle along the surface of the shell.
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    Once an object is formed with the Shell tool in ArchiCAD 15, it is possible to adjust the relative orientations of object starting and ending shapes, which begin in this parallel orientation by default.
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    Openings, such as those for windows and skylights, can be made in an extruded shell object. The 3D zone shown here has been trimmed against the shell element.
    Image: AECbytes Extra Large Image

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    SUBSCRIPTION SAMPLE

    The Magic Wand was used to automatically create this complex roof over a 3D zone, including adding portions to it for two corridors and subtracting a part of it for the central courtyard.
    Image: AECbytes Extra Large Image

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    While editing a complex roof in ArchiCAD 15, the roof form maintains its associativity, as well as connections to neighboring roof objects it has been trimmed against.
    Image: AECbytes Extra Large Image

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    In this example, the pitch of one of the corridor portions of the roof has been increased from 30 degrees to 60 degrees.
    Image: AECbytes Extra Large Image

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    ArchiCAD's Skylight tool has been improved to better support the addition of skylights to complex roofs and shells. The openings appear accurately in floor plan representations by being true vertical projections.
    Image: AECbytes Extra Large Image

     

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