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公眾號名稱：BIM譯站
公眾號賬號：BIM2018130
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有很多與BIM以及被視作BIM設計應用程序的電腦輔助設計系統相關的問題。本節將對那些最常見的問題進行解答。
基于構件的參數化建模之優點和局限
參數化建模的一個主要優點是構件的智能化設計行為。自動化的低級別編輯功能內置在程序中，幾乎就像設計人員的設計助理。然而，這種智能化需要付出代價。每種系統構件都有其自我行為和關聯。結果就是，BIM設計應用程序本身就很復雜。每種類型的建筑系統都是由以各種不同方式創建和編輯的構件組成的，盡管是在類似的用戶界面類型中將它們完成的。通常要花費數月才能精通BIM設計應用程序，進而高效地使用它。
一些用戶喜歡的建模軟件，特別是早期概念設計階段使用的SketchUp, Rhino, and FormZ’s Bonzai并不是基于參數化建模的工具。然而，它們都有一套固定的幾何編輯方式，這種編輯方式僅僅根據使用的曲面類型而變化。這種功能適用于所有構件類型，故而這些軟件用起來更容易。因此，當把應用于墻的某個編輯操作應用于樓板時，也會產生同樣的行為。在這些系統中，如果把用于定義構件類型及其功能意圖的屬性應用于所有構件類型，那么可以在用戶選擇而不是用戶創建的時候添加這些屬性。
所有這些系統允許曲面成組，為這些組命名并可為其添加屬性。仔細地完成這些并結合一個匹配的界面，就可以將構件導出并用于其它方面，例如太陽能熱吸收研究。這一點類似于人們使用AutoCAD 3D中的技巧。但是人們不會用這種建模方式用于完善設計，因為其構件沒有與其它構件鏈接，而且還必須對構件進行單獨空間管理。然而，對于初步設計來說，BIM技術與其特定構件的行為并不總能得到保證。這一點會在第五章詳細探討。
為什么不同的參數化建模軟件不能相互轉化模型？
人們常常問到為什么公司不能把模型在Revit與Bentley_建筑之間直接轉換，或在ArchiCAD與Digital Project之間轉換。從之前討論的內容來看，原因很明顯，這種互操作性的缺失正是由于不同的BIM設計應用程序依賴于它們基本構件和行為的不同定義。Bentley中的墻與Vectorworks或Tekla中的墻的行為方式不同。這些都是功能（涉及BIM工具中的規則類型和用于特定構件族定義的規則）不同的結果。這個問題只存在于參數化構件中，使用固定幾何圖元的構件則沒有這個問題。如果構件形狀能作為固定幾何圖元存在并且行為化的規則失效了，那么ArchiCAD中的構件就能在Digital Project中使用；Bentley中的構件也能在Revit中使用。這種轉換方面的問題是可以解決的。問題在于轉換構件行為（這通常不需要）。如果軟件公司就一般建筑構件定義標準（不僅包括幾何圖元也包括構件行為）達成一致，構件行為也是可以轉換的。在此之前，某些構件的轉換就會受限或徹底失敗。因了解決這些問題的需求使得實施這些方法是值得的，并且已經因此解決了多個問題，這種改進會越來越多。制造業同樣存在這樣的問題，但尚未解決。
在施工、加工和建筑BIM設計應用程序中是否存在固有差異？
同一款BIM平臺能否同時支持設計和加工深化設計？由于用于所有這些系統的基礎技術有太多共同點，所以建筑設計和加工BIM設計應用程序之間不能相互供應產品并不是技術上的原因。Revit Structures和Bentley Structures在某種程度上也發生了這種情況。他們都在開發加工級別的BIM設計應用程序中的某些功能。
另一方面，有一些使用Tekla設計并建造房屋的案例。雙方都致力于工程市場，并在較小程度上解決承包商市場方面的問題；但是，用于支持在這些信息豐富領域實現全生產應用的專業知識，取決于必要構件行為的主要前端嵌入，而這對于不同建筑系統及其生命周期需求來說是有明顯差異的。在編制構件行為時，特定建筑系統構件行為的專業知識更容易被嵌入，例如結構系統設計。軟件界面、報告以及其它系統方面的問題可能還會變化，但是處于中間地帶的軟件之間的小沖突可能會持續存在較長一段時間，畢竟每種軟件產品都想要開拓其市場范圍。
以制造為導向的參數化建模工具與BIM設計應用程序之間有很大不同嗎？
能把用于機械設計的參數化建模系統用于BIM嗎？在第2.1.3節（回復“B26”查看）和2.3.1節（回復“B32”查看）中提到了系統架構方面的差異。AEC市場已經采用了機械領域的參數化建模工具。基于CATIA的Digital Project就是很明顯的例子。同樣，Structure- works也是以Solidworks為平臺的預制混凝土深化設計和加工的應用程序。這些適應性構建了目標系統域所需的對象和行為。建筑建模工具是自上而下的設計系統，而制造領域的參數化工具最開始是自下而上的模式。由于制造系統結構中，不同部件本質上是不同的“項目”，他們已經解決了在文件之間傳遞變更的挑戰，這通常會使其更具擴展性。在其它方面，例如給排水、幕墻加工和管道工程設計中，我們可以期待看到機械領域的參數化建模工具和建筑業以及可加工級別的BIM設計應用程序在這些市場中群雄逐鹿。每個市場提出的功能范圍仍在梳理中。市場即是戰場。
原
文
There are many questions associated with BIM and the computer-aided design systems that are considered BIM design applications. This p attempts to answer the most common ones.
Strengths and Limitations of Object-Based Parametric Modeling
One major benefit of parametric modeling is the intelligent design behavior of objects. Automatic low-level editing is built in, almost like one’s own design assistant. This intelligence, however, comes at a cost. Each type of system ob- ject has its own behavior and associations. As a result, BIM design applications are inherently complex. Each type of building system is composed of objects that are created and edited differently, though with a similar user interface style. Effective use of a BIM design application usually requires months to gain proficiency.
Modeling software that some users prefer, especially for early concept design, such as SketchUp, Rhino, and FormZ’s Bonzai, are not parametric modeling–based tools. Rather, they have a fixed way of geometrically editing objects, which varies only according to the surface types used. This functionality is applied to all object types, making them much simpler to use. Thus, an editing operation applied to walls will have the same behavior when it is applied to slabs. In these systems, attributes defining the object type and its functional intention, if applied at all, can be added when the user chooses, not when it is created. All of these systems allow the grouping of surfaces, giving the group a name and maybe assigning attributes. Done carefully and with a matching interface, the object can be exported and used in other areas, say solar gain studies. This is similar to the kinds of tricks people used to do with 3D AutoCAD. But one is not going to take this kind of modeling into design development because one object is not linked to other objects and must be spatially managed inpidually. An argument can be made that for preliminary design use, however, BIM technology with its object-specific behavior is not always warranted. This topic is explored further in Chapter 5.
Why Can’t Different Parametric Modelers Exchange Their Models?
It is often asked why firms cannot directly exchange a model from Revit with Bentley Architecture, or exchange ArchiCAD with Digital Project. From the overview discussed previously, it should be apparent that the reason for this lack of interoperability is due to the fact that different BIM design applications rely on different definitions of their base objects and their behaviors. A Bentley wall behaves differently than a Vectorworks wall or a Tekla wall. These are the result of different capabilities involving rule types in the BIM tool and also the rules applied in the definition of specific object families. This problem applies only to parametric objects, not those with fixed geometry. If the shapes are accepted in their current form as fixed and their behavioral rules are dropped, an ArchiCAD object can be used in Digital Project; a Bentley object can be used in Revit. The issues of exchange are resolvable. The problem is exchanging object behavior (which is not often needed). Behavior also could be exchanged if and when organizations agree on a standard for common building object definitions that includes not only geometry but also behavior. Until then, exchanges for some objects will be limited or will fail completely. Improvements will come about incrementally, as the demand to resolve these issues makes implementation worthwhile, and the multiple issues are sorted out. The same issue exists in manufacturing and has not yet been resolved.
Are There Inherent Differences in Construction, Fabrication, and Architectural BIM design applications?
Could the same BIM platform support both design and fabrication detailing? Because the base technology for all of these systems has much in common, there is no technological reason why building design and fabrication BIM design applications cannot offer products in each other’s area. This is happening to some degree with Revit Structures and Bentley Structures. They are developing some of the capabilities offered by fabrication-level BIM design applications.
On the other side, there are a few cases where Tekla has been used to design and build houses. Both sides address the engineering market and, to a lesser degree, the contractor market; but the expertise needed to support full produc- tion use in these information-rich areas will depend on major front-end embedding of requisite object behaviors, which are distinctly different for different building systems and their lifecycle needs. Expert knowledge of specific building system object behaviors is more readily embedded when it is codified, as it is, for example, in structural system design. The interfaces, reports, and other system issues may vary, but we are likely to see skirmishes in the middle- ground for a significant period of time, as each product attempts to broaden its market domains.
Are There Significant Differences Between Manufactuing-Oriented Parametric Modeling Tools and BIM Design Applications?
Could a parametric modeling system for mechanical design be adapted for BIM? Some differences in system architecture are noted in Sections 2.1.3 and 2.3.1. Mechanical parametric modeling tools have already been adapted for the AEC market. Digital Project, based on CATIA, is an obvious example. Also, Structure- works is a precast concrete detailing and fabrication product using Solidworks as a platform. These adaptations build in the objects and behavior needed for the target system domain. Building modelers are organized as top-down design sys- tems, while manufacturing parametric tools were originally organized bottom-up. Because of manufacturing systems’ structure, where different parts were originally different “projects,” they have addressed the challenge of propagating changes across files, making them often more scalable. In other areas, such as plumbing, curtain wall fabrication, and ductwork design, we can expect to see both mechanical parametric modeling tools and architectural and fabrication-level BIM design applications vying for these markets. The range of functionality offered in each market is still being sorted out. The market is the battleground.
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上一篇：第三十九期《BIM 手冊》第二章_2.3.5節——構件管理和鏈接
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