Introduction to Geometric Modelling -CAD, BIM and GIS for building design and city models

Transkriptio

1 Introduction to Geometric Modelling -CAD, BIM and GIS for building design and city models Kirsi Virrantaus Aalto University School of Engineering Department of Built Environment

2 Content of the lecture 1. Building models in architectural and civil engineering design 2. Data models and their implementations in GIS 3. Data exchange 2

3 1. Models in architectural and structural building design Architects make models about building designs, these designs are then further designed by engineers and finally built, used and maintained The models should cover the entire life cycle of buildings In addition to traditional CAD software and CAD models also BIM (building information models/rakennuksen tietomalli) are used The differences between CAD and BIM models are in: Dimensionality Data model Data contents Purpose 3

4 Typical floor plan in 2 dimensions 4 2d floor plan

5 3 dimensional BIM model of a building BIM model of a building; geometry can be of Brep-type geometry, attributes in relational data base (Vilpas,S., MSc thesis) 5

6 Geometric models in CAD&BIM Data models Simple CAD softwares were 2d with simple array type data storage Modern CAD offer 3d-models as well, but not always with full topology BIM models are based on RDBMS and topological geometric model (for example Brep type) Data contents and purpose In RDBMS vast amount of data can be managed, from technical details to costs BIM is a concept that extents CAD for the use and maintenance of the buiding as well as supports data exchange between different professionals during the design and construction 6

7 The level of detail in the model LOD describes the level of detail of, for example the building model LOD = level of detail; mostly descibes the LOD of geometry LOD means originally the optimization of a mesh model of a 3d object fro visualization purposes LODdding is in principle same process than so-called generalization in cartography; the details of less importance are deleted In city models by CityGML there are 5 LOD-levels (0 4) for different purposes

8 Mallin yksityiskohtaisuus mallin yksityiskohtaisuutta kuvataan ns. LODien avulla LOD = level of detail; liittyy useimmiten vain geometriaan LOD tarkoittaa alun perin esim. kolmioverkolla esitetyn 3d-objektin optimointia/yksinkertaistamista visualisaatiota varten LODdaus on periaatteessa samaa kuin yleistys kartografiassa: vähemmän merkityksiset yksityiskohdat jätetään pois Esim. CityGML tuntee viisi LOD-tasoa (0 4) eri tarkoituksia varten

9 9 Female head in three different LODs

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11 PhD research on procedural modeling in CityGML environment 11

12 Brep-model The model is composed of geometric features and topological relaationships; face, edge, vertex arelinked to each others IFC schema that shows B-rep-model of an object IFC = Industry foundation classes; Open file format specification for BIM software Schema in which objects are linked by relationships Lähde:

13 Brep-malli Muodostuu geometrisista osista (geometric features) ja topologisista relaatioista; esim. face, edge ja vertex Esimerkki IFC skeemasta jossa esitetään kappaleen B-rep-malli Kaavioesitys, jossa kohteet yhdistetään relaatioilla (osa topologisia) Lähde:

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15 IFC schema showing data contents on different LODs 15

16 Challenge of integration: 3D model of a building and GIS surface model 16

17 2. Models in geographic information systems In GIS we make models on surface of the Earth (elevation models) natural objects (trees, lakes, rivers, forests, fields ) man-made objects (buildings, streets, roads, bridges ) For modeling of surface of the Earth we use grid structured elevation models irregular triangular networks The speciality of GIS is the reference system, the coordinate system and the location of the origin ( see more on cooordinate systems in Finland in and For modeling of natural and man-made objects and phenomena we use objects and (objektit) field models (kentät, jatkumot) 17

18 (TIN-model, Martin Vermeer, 2015) 18

19 Laser scanned shapes of the terrain; elevation and trees (and other pobjects) can be algorithmically identified and modeled into separate models (elevation and objects) ( 19

20 Krooks,A, 2013)

21 3d model of an object created by using photogrammetrically measured points (Martin Vermeer) Petri Rönnholm, TKK Measurement of the sea level change by using mareography Analysis of a major flood causes by using GIS elevation model Antti Veijalainen, d-työ; 2008) 21

22 2D models starting point for geometric modeling in GIS In late 60 s Simple tools for drawing Graphical drawings digitized into so-called spaghetti files; flat files including points, lines and polygons without any relationships In 80 s spatial data model development and tailored software for spatial data management topology and topological data models In 90 s and later: regular use of relational data bases for geographic information; RDBMS + spatial extensions Oracle Spatial, PostGIS See more in

23 Drawing made of points, lines and polyons without any relationships between them. (Vilpas, S., MSc thesis)

24 Topology Topology is maybe the strongest development in the geometric models also for GIS Geometry is presented by: points, curves and surfaces (often called as points, lines and areas in GIS) When topology is considered we often use the terms: vertices, edges, faces; Most popular topological relationships: adjacency, connectivity You learn topological data structures, like DCEL, later in this course

25 TIN as a topological data model, the relationship adjacency is used to represent topological information; this model supports algorithm better than list of coordinates 25

26 GIS data model types For modeling of natural and man-made objects and phenomena we use discrete objects (diskreetit kohteet) field models (kentät, jatkumot) Speciality of GIS is that data is georeferenced, data has positional data (coordinates) in a map coordinate system Most often CAD softwares use their own coordinate systems, in which origin can be anywhere (like lower left corner) In GIS topological data structures are used for processing the data; mostly data is stored in relational data bases with spatial extension In CAD quite often simple flat file structure is used for storing BIM utilizes data bases for attribute data and topological data model and structure for geometry 26

27 Object model Object, like a building, is made of parts like walls, windows, doors, roofs In GIS and related CAD and BIM parts are modeled most often by using points, lines and polygons (vertices, edges, faces) Models can be of varying level of details (LOD) The basic elements of object models piste (point, vertex), viiva (line, edge) ja alue (polygon, face) Data models and data structures use topological relationships (like B-rep) in GIS they are not called B-rep; B-rep term comes from solid modeling now, when GIS and BIM (and CAD) are integrated, also the terminology is sometimes transferred at east it is sometimes confusing Object type data can be easily stored into RDBMS; spatial extensions for supporting search and analysis

28 Objektimalli Kohde, esimerkiksi rakennus, koostuu osista, kuten seinät, ikkunat, ovet katot Osat on mallinnettu joko kappaleina tai reunaviivoin Mallin yksityiskohtaisuus riippuu osien yksityiskohtaisuudesta (vrt. LOD) Kohdemallinnuksen peruselementit ovat: piste (point, vertex), viiva (line, edge) ja alue (polygon, face) topologisia relaatioita hyödyntävät tietomallit (kuten B-rep) Objektimallinen tieto voidaan tallentaa relaatiotietokantaan (RDBMS); spatiaaliset laajennokset tukevat hakua ja analyysiä

29 Field model Field model is used for representing continuous phenomena Elevation, land use, soil types Fields can be presented by Raster/voxel models consisting of pixels or voxels Point clouds Polygon networks Contours The decision whether to model as object or field is not on the data type For example: a lake can be modeled as a polygon (discrete object), but also as a field called lakeness 29

30 Kenttä/jatkumo Kenttämallina mallinnetaan jatkuvia ilmiöitä Korkeusmalli, maankäyttö, maaperä Kenttämalli voidaan toteuttaa Rasteri/vokseli rakenteena, joka koostuu pikseleistä, voksleista Pistepilvenä Polygoniverkkona Korkeuskäyrinä Päätös siitä käytetäänko kohdemallia vai kenttämällia riippuu siitä kuinka asia halutaan nähdä esimerkiksi: järvi, joka tyypillisesti vaikuttaa olevan kohde (diskreetti kohde), voi olla myös kenttä järvisyys 30

31 Voxel models/ raster models Maybe the most popular implementation of field type data is 2d or 3d raster; pixels and voxels One reason for popularity is the simple storage in matrix structure; also data collection often supports matrix structure Voxels are three dimensional space elements, most often small cubes (solid object) Each voxel has one or several attributes and objects are made based on that information The challenge of voxel models is that when the resolution is improved the amount of voxels is increasing This problem can be solved by compressing the data In 2d for example quad tree, in 3d oct-tree

32 Vokselimallit/rasterimallit Ehkä suosituin toteutus kenttämalliselle datalle on 2d tai 3d rasteri; pikselit, vokselit Suosion syy on helppo tallennusrakenne, matriisi Myös monet tiedonkeruumenetelmät tuottavat matriisimuotoista dataa Alkiot ovat vokseleita, useimmiten kuution muotoisia Jokainen vokseli saa ominaisuustiedon ja sen mukaisesti rakentuvat kohteet Vokselimallinnuksen haaste on resoluution parantuessa tapahtuva vokseleiden määrän kasvu tämä ratkaistaan tiivistysmenetelmillä (esim. kahdeksanpuu; oct tree; 2d:ssä nelipuu)

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34 Grid model of the sea bottom/merenpohjan gridimalli (Outi Nyman,2011) 34

35 Laurini & Thompson, 1992; Fundamentals of Spatial Information Systems

36 Geometry, topology and coordinates in matrices geometry pixels as squares, hexagons square pixel 4 neighbours joint edge 8 neighbours joint edge or corner hexagon pixel 6 neighbours joint edge 6 neighbours joint edge or corner

37 implicit topology need not to be coded joint edge - adjacency joint edge or corner - connectivity resolution, orientation and origin And same definitions in 3d

38 quad tree (Samet,H., The Design and Analysis of Spatial Data Structures) one special type of block encoding the area is divided into smaller areas according to the requirements of the data in addition to compression also for indexing linearization of 2d matrix space filling curves lossless

39 Quadtree for 2d Octtree for 3d Laurini,R., Thompson,D., Fundamentals of spatial information systems, 1992

40 TIN model Can be created from any point set: laser scanned point cloud, field measurements In an optimal TIN trianges are as equilateral as possible TIN can be dinsified, points can be added; then TIN must be calculated again, local optimization by Well-formed triangles fulfill the Delaunay criterion (or empty-circle criterion) a unique circle drawn through the vertices of a triangle (circumscribing circle or circumcircle) does not contain any vertices of the triangulation the circle may cut any number of edges and other vertices may lie on the circle

41 Some constraints added in order to keep the shape of the valley

42 4. Data exchange Most CAD software have their own main memory data structures which are not documented Transfer formats between GIS softwares are used SHAPE developed by ESRI for geospatial data trasfer, informal standard Many other formats for transfer exist For BIM IFC Industry foundation classes, ISO/PAS 16739, standard for object oriented data transfer Data exchange is a challenge that is not yet totally solved; later in this course this topic will be discussed more