Exam

BIM uses cases define the purpose of a BIM model and thus its content.

LOG: Level of Geometry defines which maturity geometry objects must have in different phases

LOI: Level of Information defines which types of object have to posses which properties (semantic information)

Digital representation of a physical or immaterial object or process from the real world in the digital world

Uniclass

Omniclass

CAD quantities are component-oriented (one component several tasks) while LV quantities are task-oriented (one task several components)

gbXML

IFC4

IFC is a Element-based Volume Model

CityGML is a Surface Model

Daylighting, Energy, Wind, Solar studies, LCA (Life Cycle Analysis),

A 3D City Model is a digital model of urban areas. Some of its components are waterbodys, vegetations, transportation objects…

CityGML (City Geographic Markup Language) is a standard for storing and transferring virtual 3D city and regional models.

Reachability analysis, site analysis, management of cultural landscape, simulation of natural risks, city information system, management of ski runs

LOD stands for “Level of Detail”.

We distinguish between five (5) LOD as follow:

·       LOD 0 – Regional Model: 2.5D digital terrain model

·       LOD 1 – City Model: block model but no roof structure

·       LOD 2 – City Model: roof structure with optional texture

·       LOD 3 – Site Model: detailed architectural model

·       LOD 4 – Interior model: Walkable interior spaces

Standard STEP (STandard for the Exchange of Product), ISO 10303

VR is a virtual environment that mimics the real world while AR is the addition of virtual objects to real objects (done virtually though).

Examples: VR – CAVE, HMD;

AR – DEPLANAR (Augmented Architecture), Google Maps Live View

EXPRESS

    Property Sets can only be used to store information that is part of the standardized IFC schema.

It allows to exchange both semantics and geometry, also allows different geometric representations for one semantic object.

The IfcBuildingElementProxy is a proxy definition that has the same function as any subtype of the IfcBuiltElement but without having a predefined meaning of the special type of building element it represents.

Example: Bearing Bridge

Tessalated BRep, Swept Solid, CSG Primitive, BRep.

It is a subset of the full IFC schema that defines mandatory and optional objects/attributes.

IFC2x3 Structural analysis view, IFC2x3 Coordination view, IFC4 Reference view, IFC4 Design transfer view…

A schema describes the data model of IFC (class hirachy, classes and their properties)

An instance represents an actuall object implementing a class definition of this schema.

Provides a catalog of parametric object types which posses geometric and semantic attributes

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Consistency, design coordination, quantity take-off, simulation basis, rendering

Geometry describes properties such as shape, curvature, inclination etc. while the Topology describes the relationship between faces, edges, and vertices.

·       Domain Specific CAD/BIM System

·       General purpose CAD system

·       Geometry Kernel

·       Low level Graphics Routines

·       Hardware

Sweeping, Lofting, Extrusion, Rotation

Indexed Face Sets are more memory efficient because the vertices are stored only once while in Triangulated Face Sets they are stored more than once.

The explicit approach describes an object by its boundaries,

while the implicit approach describes an object by the procedural description of its construction history:

Object-based Parametric-, Geometry-based Parametric- and Parametric BIM- Modelling

The dimensional constraints define the span/extension of an object/component while the geometric constraints apply to the relation of that object/component with regard to other objects/components.

Collinearity, concentricity, tangentiality, coincidence, circumscription, inscription, perpendicularity

·       Reduction of planning errors,

·       Reduction of errors in tendering,

·       Increased transparency in project execution,

·       Improved communication with the public.

Concurrency control is the locking of an object while it is being modified by a user. It is necessary because it prevents simultaneous modification of an object in the model by two or more users, otherwise there could be conflicts/issues with the models.

Implicit approach (lock is activated automatically) and explicit approach (lock is requested by the user).

Model federation is the independent creation of an own model by each involved discipline, which are then all coordinated/merged at frequent intervals into a federated model. It is defined the ISO EN DIN 19650.

In an explicit synchronization, the synchronization is done on request by user while in implicit synchronization it is done automatically in the background.

locking is done automatically while explicit locking is invoked and released by the user.

       Work-In-Progress (WIP),

·       Shared,

·       Published,

·       Archived.

State what the abbreviations mean:

• EIR: Employer’s Information Requirement,

• BEP: BIM Execution Plan

Explain both terms and put them in context to each other:

The EIR is a document by the employer where he specifies the goals (BIM, purposes, use cases…) and expectations (Model extent, model content…) of the projects, while the BEP is a document by the bidder in response to the EIR where they define in detail how they will go about to meet those goals and expectations.

OIR (Organisational Information Requirement) is a document that deals with the organisational aspect of the projects (when client has many of them), and it contributes to the PIR (Project Information Requirement) which is a document defining the requirements for one specific project (sort of EIR for that project).

The Black-Box method is a code compliance checking process in which only the ingoing and outgoing information is visible, but not the checking procedure itself. It has the major advantage of having a comparatively low error rate of the overall process; the disadvantage is that extensions and modifications are only possible by incorporating the software vendor.

While the White-Box method makes the internal processing steps comprehensible for the user. It presents major advantages for the execution of a checking task, but it requires significantly more effort to develop and implement.

Issue tracking is a process used to track, manage, and resolve issues or problems related to the BIM models upon which different teams/stakeholders are collaborating.

The BIM Collaboration Format (BCF) is the current structured file format suited to issue tracking.

A BIM is a digital representation of physical and functional characteristics of a facility. With this it serves as reliable source of information about facility which will be helpful in its life cycle.

Three characteristics: 1. Three-dimensional Geometry 2. Semantic information (walls, doors, slabs etc. which help in quantity take off and simulation). 3. Additional information such as material properties.

·       Reduction of planning errors: increased transparency over 2D design. Increase coordination among disciplines and single source of truth leading to improved data management.

·       Reduction of error in tendering: model-based quantity takes off.

·       Increase of transparency in project execution: because of model based construction progress monitoring.

·       Improved communication with public and people attached to the project.

·       Early conflict and clash detection, proper data storage and management.

·       Better data quality; life cycle building management.

·       Budget reliability; no change order

·       Collaborative design gives higher building functionality.

·       Fast project delivery

·       Virtual simulation and rendering.

·       Prefabrication which reduces accidents on job site.

·       Reduction of error and extra efforts which arise due to manual addition of information in each phase.

·       Easily handover building information to the owner for its use in operational phase.

·       Cost efficiency, increase of productivity in construction, clash detection.

·       line drawings cannot be comprehensively understood by computers.

·       Basing the information flow on drawings alone often lead to errors

·       Design changes are particularly challenging: if they are not continuously tracked and relayed to all related plans, inconsistencies can easily arise and often remain undiscovered until the actual construction.

·       The conventional drawings cannot be used directly for downstream applications such as simulations, analysis, rendering but must be put into manually thus involve additional effort, cost and errors.

·       After project realization, the owner must put an extra effort and cost to insert information from these drawings into facility management for building operation thus accepting extra cost, effort and errors.

ü   A geometric modelling kernel is a software component that provides 3D modelling capabilities in computer-aided design (CAD) software.

ü   This is a software component that provides support for elementary data structures and operations for representing and processing geometric information. Two examples of commonly used geometric modelling kernels include ACIS (Spatial 2015) and ParaSolid (Siemens 2015).

Xplannung: open standard for digital exchange and archiving of land use plans, landscape and regional plans

GML: city geography markup language.  It is Standard for storing and transferring virtual 3D city and regional models.

2D = simple CAD drawings

3D = Three-dimensional geometry

4D = Geometry + time scheduling

5D = Geometry + time scheduling+ cost

6D = Geometry + time scheduling+ cost+ Energy information

7D= Geometry + time scheduling+ cost+ Energy information + facility management

STL, VRML, 3DX are geometry only formats. Geometry only formats contains no semantic information therefore no downstream application.

It is the standardized data model for the exchange of Building Information Models. developed and maintained by building SMART. Building SMART is nonprofit organization which maintain and develop building standards. IFC is based on ISO standards STEP and has version of 10303.

In order to hand over data to clients and to enable coordination between different disciplines working on project. Model hand over to following design phase and consistency in the model.

A model view defines a subset of the full IFC schema which defines mandatory and optional objects / attributes.

Some pre-defined views are:

IFC 2x3 ▪ Coordination view ▪ Structural analysis view ▪ Facility management handover view

IFC 4 ▪ Reference view ▪ Design Transfer View

downstream application (simulation, rendering)

help in clash detection.

Help in BOQ and cost calculation, tendering, bidding.

Better presentation and communication with client.

Past: data are shared through Gmail which lack consistency. It involved manual effort and difficulty in merging.

Present: files are managed and shared on central server called project platforms. In this server, files are accessed, updated and managed by multiple stake holders. The problem we face today is that at these servers a whole model is deal as big block. This make it hard to track changes. Also, simultaneous modifications in the model is not possible.

Future: cloud platforms will be used to manage models and not files. More consistency and transparency. Low errors and easy modifications and its tracking.

Tools: BIM 360, Graphisoft BIM server, Revit server etc.

Good for only plane faces • curved surfaces → many triangles • vertices are stored multiple times • neighbourhood relationships are not stored → gaps and overlaps are hard to detect.

Bezier curves:

The basic function for bazier curves is P = n-1. Where n is the number of points and p is degree of polynomial. The more the n, the higher is the degree of polynomial. Changing the position of one control point, therefore has global impact on the entire course of the curve.

B-Splines:

Splines were developed to overcome the limitations of Bezier curves. The primary advantage is that the degree of the curve can be defined largely independently of the number of control points. As such, it is possible to combine the smoothness of low degree polynomials (typically p = 3) with a higher number of control points. More smoothness and freedom.

Similarity:

§  Arbitrary number of control points

§  Passing through first and last control point

§  Tangential with first and last segment of the control point polygon

Difference:

 >> local impact of control point on curve.

NURBS (Non-uniform rational B-splines): Problem with B splines curves is that we cannot create circles, ellipses, parabolas, hyperbolas using B-Splines.

Thus give every control point a weight. This makes it possible to further influence the course of the curve, which is necessary to precisely represent regular conical sections (circles, ellipses, hyperboles).

It is the term given to any technique, which generates movement from single (predefined / static) images. It generates a dynamic scene composed of number of frames, which can be played as a film (precalculated process).