Budapest Tech John von Neumann Faculty of Informatics Institute of Intelligent Engineering Systems Introduction to virtual engineering Lecture 4. Construction of shape in the model space László Horváth WWW.nik.hu
CONTENTS 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
Contextual modeling of structures of shapes Visualization Associative characteristics Visualization of bodies Scene Solids Relationships of solids Animation Projection Combination Placing Rendering Position, scale Modification Movements Volume Surface characte-ristics Shape Form feature Analysis of solids Hair, particle Volumetric Bended sheet Texture Simulations Geometry Conditioning Local characteristics Collisions Surface Movements Contour
A B A B Constructive solid geometry Union Difference Intersection Primitives A - B B - A A, B A - B
Modification of initial shape by form features Volume subtracting shape modification Creation of body by tabulation Form feature Modified shape Base feature
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.
Reference planes Contour based form features
Conditioning (dress-up) form features Chamfer Fillet Shell Draft
Fillet form features Constant radius Radius changing according to a law Linearly changing radius Defined by boundary curve curve (law) spine Corner fillet Filleting with automatic removal of topological entities
E E E n - neutral edge n n1 E P P P n2 P P n P n Draft form features p p p p E n E n F F F d d d F pl pl d , Extrapolated fillet surface Outside neutral edge
Irregular model construction: bended and cut sheets Bend panel Fitted edges Bend Form feature It is not a bend!