Download Solid-Modelling-Internals

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/FeatureWorks
CFL/Blend Recognition and Suppression
CollabView
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 C2 on
face F intersect the
curve C1?
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 B1 and B2
• 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 2d-fragment
of a surface.
• Edge-the 1d fragment
of a curve
• Co-edge-edge as an
element of a face
• Vertex-0d 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 F2
boundary along
e1, then F1 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
Topology Details