INTRODUCTION TO GEOMETRIC MODELLING

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# INTRODUCTION TO GEOMETRIC MODELLING - PowerPoint PPT Presentation

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

20 September 2010

Content

• Introduction

• Types of 3D model

• 2D vs 3D

• Solid Modeling

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

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

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

3D Surface Modeling

– has material/texture between the line of

frame

– normally no thickness

be produced

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

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

Solid Modeling

• Several different types of solid modeling

– Primitive modeling

– Constructive solid geometry (CSG)

– Feature-based modeling

Primitive Modeling

• Objects described using basic geometrical forms.

• Common geometric primitives.

Constructive Solid Geometry

• More flexible and powerful than primitive.

• Allow Boolean

Operations: union, difference & intersection

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.

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*

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

3D Ops: Revolve
• The profile is rotated around

a defined axis, 0 – 360 degree

• Cross-section is constant

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