Introduction to virtual engineering

László Horváth WWW.nik.hu

Budapest TechJohn von Neumann Faculty of Informatics

Institute of Intelligent Engineering Systems

Lecture 4.

Construction of shape in the model space

Contextual modeling of structures of shapes

Constructive solid geometry

Modification of an initial shape by form features

About building of topology

Main groups of form features

CONTENTS

Contextual modeling of structures of shapes

Solids

Combination

Modification

Form feature

Volumetric

Conditioning

Surface

Relationships of solids

Placing

Movements

Contour

Volume

Analysis of solids

Simulations

Local characteristics

Geometry

Collisions

Movements

Associative characteristics

Visualization

Visualization of bodies

Animation

Position, scale

Shape

Hair, particle

Scene

Projection

Rendering

Surface characte-

ristics

TextureBendedsheet

Constructive solid geometry

IntersectionDifferencePrimitives Union

A, B A B A BA - B B - A

A - B

Modification of initial shape by form features

Base feature

Form feature

Creation of body by tabulation Volume subtracting shape modification

Modified shape

Extended topology of boundary

Building topology using Euler operators

MEV – make edge and vertex! MEF– make edge and face! KEMR – kill edge and make ring (closed chain of edges)!

Start building of topology

Edge removal and vertex merging operations result a model that consists of single edge and single polygon.

Main groups of form features

1. Defined by type, volume adding and volume subtracting

Cuboids, cylinder, sphere, cone, and torus.

2. Contour based, volume adding and volume subtracting

Tabulated (extruded), revolved, pyramid, tube, swept, and lofted.

3. Transformed, added and volume subtracted volume.

Constructive solid geometry in shape modification

4. Modification of shape by surface

Building separately created surface.

5. Form features for conditioning existing form features (dress-up features)

Fillet, chamfer, shell, and draft.

Contour based form features

Reference planes

Connecting surface and solid

Intersection of solid by surface (sewing)

Conditioning (dress-up) form features

FilletChamfer

Draft Shell

Fillet form features

spine

curve (law)

Constant radius Radius changing according to a law

Linearly changing radius

Filleting with automatic removal of topological entitiesCorner fillet

Defined by boundary curve

Draft form features

p

En

Fd

p

Fd

En

p

Fd pl

En2

En1

p

Fd pl

En

Pn

PPP

nP

P,

Extrapolated fillet surfaceOutside neutral edge

En - neutral edge

Opening solid at surfaces to create shell

Irregular model construction: bended and cut sheets

Fitted edges Bend

It is not a bend!Form feature

Bend panel