SolidModellingInternals The modeller GUI The Husk Geometry Kernel

Solid-Modelling-Internals

The modeller GUI The Husk Geometry Kernel . stl . sldprt . sat

Basic Components • GUI-provides a rendering/viewing facilities. Provides modelling ease • Husk-Implements operations, controls and manages the parametrization and the solid • Kernel-maintains the basic geometry. Answers geometric queries posed by the husk.

Post-Modeller Analysis Husks In this case: Curvature Analysis

GSSL Husks – – AFR/Feature. Works CFL/Blend Recognition and Suppression Collab. View CAMWorks The Husk-Kernel Interface is very important

The GUI • Present a Co-ordinate system • Make selection and design of entities easy • Provide interfaces to down-stream analysis and recently • Provide for collaborative design! GUI can make-or-break

The Husk Front Office • Implements Operations (gets it done from the kernel). -extrudes/revolves/sweeps -extract parameters and use kernel operations • Maintains design tree and modifications and alerts user! -maintains the sequence and dependence of the operations -maintains parameter consistency

The Husk Back Office • Maintains relationships between geometric entities -such as between counter-bores/assemblies -across features • Re-sequences operations -roll-back and re-do -record such inter-dependency

Implements operations…. 1. Takes the scribe and prepares the Cylinder. 2. Subtracts the cylinder

Maintains and updates design tree…. . Alert The User!! Deepen the hole

Relationships between geometric quantities…. Counter-Bore Holes Maintain coaxiality of the two cylinder axes

Re-sequences operations Desired Husk Operation. Kernel Operation • Blend the edge first. • Then do the boss

Kernel • Maintains the solid as faces/edges/vertices • Implements operations such as booleans, offsets, and even blends • Supplies answers to geometric queries

Routine Operations • Booleans • blends

A typical Query… Does the curve C 2 on face F intersect the curve C 1?

Another query from a CAM husk • What is the distance between faces S and S’? S Can the ball cutter go in? S’ CAM picture

Kernel Operations Kernel typical APIs: • Is this point on this face? • Find the closest point to p on surface S • Intersect solids B 1 and B 2 • Compute tangents

The B-Rep of a solid • Boundary of a solid as a closed surface. • Inside/Outside and a outward normal • Surface composed as a collection of faces/edges/vertices Face Edge vertex

Basic Entities • Face-the 2 d-fragment of a surface. • Edge-the 1 d fragment of a curve • Co-edge as an element of a face • Vertex-0 d element of design space. • All quantities in design space • Two-tier representation - combinatorial or topological - parametric or geometric

Topology • Adjacency relationships between face/edge/vertices • Orientation All objects here have the same topology.

Topology cont. • Face-a collection of loops • Loops-sequence of signed edges • Edge-ordered pair of vertices • Vertices-just a Set

Applications of Topology Husk: check topology! And alert user.

Applications of Topology-II Kernel: Helps in sequencing intersections. If F intersects F 2 boundary along e 1, then F 1 is next.

Wrap-Up • The GUI-Husk-Kernel trichotomy • Husk-as the legislative body of operations • Kernel-as the executive body Kernel Representation: Geometry/Topology Details