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INTRODUCTION TO GEOMETRIC MODELLING

INTRODUCTION TO GEOMETRIC MODELLING. 20 September 2010. Content. • Introduction • Types of 3D model • 2D vs 3D • Solid M odeling. Introduction. 3D modeling is creating an object or a part which has 3D characteristics and can be viewed 3D

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INTRODUCTION TO GEOMETRIC MODELLING

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  1. INTRODUCTION TO GEOMETRIC MODELLING 20 September 2010

  2. Content • Introduction • Types of 3D model • 2D vs 3D • Solid Modeling

  3. Introduction • 3D modeling is creating an object or a part which has 3D characteristics and can be viewed 3D • Simply, the object has depth or thickness • In 2D drafting or drawing, the object is normally drawn in XY direction. • In 3D modeling, the object is drawn in XY and also Z direction

  4. 3D Modeling

  5. Object modeled in 3D can be rotated and view from any angle• Generally, more complicated to create and producecompare to 2D

  6. Types • 3 main types: wireframe, surface and solid • 3D Wireframe Modeling – Show the ‘frame’ of the object in lines – quite similar to 2D, however the object has 3D characteristics

  7. 3D Wireframe Modeling

  8. 3D Surface Modeling – has material/texture between the line of frame – normally no thickness – complex/advance curved surface may be produced

  9. 3D Surface Modeling

  10. 3D Solid Modeling – model is made from solid blocks by combining and/or subtracting – the solid blocks can be created by applying 3D operations on 2D object and/or adding and subtracting primitives

  11. 3D Solid Modeling

  12. 3D Vs 2D

  13. 2D Vs 3D

  14. Solid Modeling • Solid model consist of volumetric information & surface info of an object • Surface of the model represent boundary between outside & inside of the object • Basic rule – all surfaces must touch another surface

  15. Solid Modeling

  16. Solid Modeling • Several different types of solid modeling – Primitive modeling – Constructive solid geometry (CSG) – Feature-based modeling

  17. Primitive Modeling • Objects described using basic geometrical forms. • Common geometric primitives.

  18. Primitive Modeling

  19. Primitive Modeling Example:

  20. Constructive Solid Geometry • More flexible and powerful than primitive. • Allow Boolean Operations: union, difference & intersection

  21. Boolean operation

  22. CSG: Example

  23. CSG: Example

  24. Feature-based Modeling • 3D model is built using series of features, such as hole, slot, square block, etc. • Each feature can be independent or linked to other feature. • The geometry of each feature is controlled by modifiable constraints and dimensions.

  25. Feature-based Modeling

  26. FBM: 3D operations • Basic concept – 2D cross-section or profile is produced – Depth is given to the profile • Generally 4 types – Extrude – Revolve – Sweep – Blend • *different terms might be used in different software/books*

  27. 3D Ops: Extrude • A linear sweep, where the profile is given a depth in straight line, perpendicular to the profile plane • Cross-section is constant, start – end

  28. 3D Ops: Extrude

  29. 3D Ops: Revolve • The profile is rotated around a defined axis, 0 – 360 degree • Cross-section is constant

  30. 3D Ops: Sweep • The new command and is similar to the EXTRUDE command, but it concentrates on using paths to define the direction of the extrusion. • This command SWEEP a 2D object along a path

  31. 3D Ops: Sweep & Blend

  32. Steps in building 3D object

  33. Examples of FBM + boolean

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