Stayout Zone Drawing Add stayout zones if desired. A stayout zone is any convex region of the part space that the user wants to be excluded from consideration in fixture computation. For example, you would want to exclude any edge that is to be worked on while the part is held in the fixture. Click the Add Stayout button to add a stayout zone. Click the mouse to indicate the stayout zone vertices. Click the Close Stayout button to complete the stayout zone. The user may add up to 20 convex stayout zones. Concave polygonal stayout zones may be accommodated by drawing several convex stayout zones.
Fixture Synthesis When you have drawn the part, click the Compute Fixtures button to begin the fixture set computation. The progress of the computation will be shown in the status text window. The fixture synthesis runs in a separate thread so you may continue browsing during a particularly long computation. Just back up to the FixtureNet III page from time to time to check the result of the computation. When done, the first (best) fixture will be displayed in the fixture display area. If more than one fixture is found, step through them with the Next and Previous buttons. If no fixtures were found, you either drew the part too small (so it slips through the fixture grid) or you specified stayout zones such that no fixture is possible. The fixtures are sorted in order of a quality metric that favors an even distribution of reactions on the fixels.
Stock Parts Stock parts for testing and benchmarking may be loaded by clicking the Start New Part button and then clicking the upper right corner of the frame around the part drawing window. Repeat to cycle through the available stock parts.
Drawing Snap The drawing snap can be set to 5, 10, or 25 pixels (equivalent to 0.1, 0.2, and 0.5 part space units, respectively). When in drawing mode (after clicking the Start New Part button), click on the lower right corner of the frame around the part drawing window. Additional clicks will cycle through the available snap settings back to the default zero (single pixel resolution).
<applet
code="Fixture2D.class"
width=800
height=1200>
<param
name = "ClampType"
value = "1">
<param
name = "QualityMetric"
value = "0">
<param
name = "ClampFilter"
value = "1">
<param
name = "RespectVertices"
value = "0">
You need a Java-enabled browser to see the applet.
</applet>
A ClampType of 0 is a simple circular locator. ClampType 1 is a bullet-shape.
With QualityMetric set to zero, the generic quality metric is used (see the
PhD Dissertation of Rick Wagner). When set to 1, the fixtures are sorted in
order of configuration angle. With ClampFilter set to 1 the type 1 clamps
are filtered for interference withe the locators and the part itself.
When RespectVertices is set to 1, fixtures with any vertex closer than
a fixel radius to any locator are filtered out.
Class: Description: DisplayArea.class Extends Canvas DrawingArea.class Extends Canvas Edge2D.class 2D edge object EdgeSet2D.class Encapsulates a vector of Edge2D objects EdgeTriple2D.class A triple of Edge2D objects Fix2D.class Fixture object Fixture2D.class Applet class for the GUI FixFun2D.class 2D fixture functions FixtureSet2D.class Encapsulates a vector of Fix2D objects FramedDrawingArea.class Extends Canvas FramedDisplayArea.class Extends Canvas Geom2D.class 2D geometry function library IntSet2D.class Set of integers Part2D.class 2D part with stayout zones PartConfig2D.class 2D part in contact with three locators and a transform Point2D.class 2D point VofV.class Encapsulates a Vector of Vectors for 2D array operations
The relationships among these classes are shown in the diagram below:
The Fixture2D has a Part2D object which is the input part drawn by the user. It also has a FixFun2D object named FF which is used to pass the input part to for "growing." The grown part is returned by FF. Hence, Fixture2D "has two" Part2D objects. The grown part is then passed to FF and a FixtureSet2D named FS is returned.
public Part2D GrowPart(Part2D P)is passed a part as a Part2D object and returns a grown part as a Part2D object. The grown part has its edges moved outward by a fixel radius (passed to the FixFun2D object when it is created), and trimmed by themselves (in concavities) and by any grown stayout zones.
The second public function, the fixture synthesis engine
public FixtureSet2D ComputeFixtures(Part2D P, TextArea StatusText)is passed a grown part and a TextArea object for status reporting and returns a set of fixtures as a FixtureSet2D object.
These functions may be called from a java application as shown in the examples below:
public Part2D ThePart = new Part2D(); public Part2D GrownPart = null; float FixelRadius = (float) 0.25; // Half inch diameter locators public float PixelsPerUnit = 50; public FixFun2D FF = new FixFun2D(FixelRadius); public FixtureSet2D FS = new FixtureSet2D();The input part (ThePart), the grown part (GrownPart), the fixel radius (FixelRadius), the FixFun2D object (FF), and the returned fixture set (FS) are declared as instance variables in the Java application. They are declared public because they need to be referred to from the display and drawing area Canvas-derived objects.
if (e.target == ComputeButton)
{
AddStayoutButton.disable();
StartButton.disable();
ComputeButton.disable();
PartPic.DA.NewPoint = null;
// Begin fixture set computation
GrownPart = FF.GrowPart(ThePart);
// Display the grown part and stayouts
iProgress = 1;
FixturePic.DA.repaint();
SynthesizerThread = new Thread(this);
SynthesizerThread.start();
}
The GrowPart() function is called within the action() function (using the old Java
event model because the Java 1.1 event model is not supported by many browsers today).
A new thread is created to run the fixture synthesis because it is generally time
consuming and users don't like being trapped. Starting a new thread lets users
continue to use their browser while the fixture computation runs.
public void run()
{
FS = FF.ComputeFixtures(GrownPart, StatusText);
if (FS.n > 0) giCurFixture = 1;
// Display the first fixture of the returned set
iProgress = 2;
FixturePic.DA.repaint();
StartButton.enable();
if (FS.n > 1) NextButton.enable();
sbStatusBuffer.append("\n");
}
The thread statements are executed in the run() function. The ComputeFixtures()
function is called as a public method of the FixFun2D object, FF. FS is the returned
FixtureSet2D object. The FixturePic.DA (display area of the framed display area)
paint() event is triggered by the repaint() function. The paint() event code draws
the current (default = 1) fixture from the fixture set.
All geometric functions use single precision floating point arithmetic. The zeroeth element of all arrays and vectors is reserved for object swap space (the first element of any array or Vector has the index 1).
Version Date Description
1.00 May 1, 1997 Prototype for GUI feedback. Synthesis engine non-functional.
1.24 June 10, 1997 Alpha test version, fully functional. The Compute Fixtures,
Next Fixture, and Previous Fixture buttons were moved closer
to the fixture display area. Thanks to Charles Anderson for that
suggestion.
1.30 June 16, 1997 Beta test version. Fixes the vertical line self-trim bug and the
non-diamond grid third locator leak bug. Adds three stock parts
for loading and drawing snap options as advanced features.
1.33 June 18, 1997 Adds F2DStatClient object for communicating with a Java server
(F2DStatServer.class) to collect statistics on the user parts
submitted and fixture sets returned. If no connection is made
to the server, the F2DStatClient is destroyed. If a connection
is made, the client object gets a session ID from the server
and then stops listening. Part data are then sent for each
new part submitted for computation, and fixture set data are
sent for each fixture set computed. Statistic data are written
to a file by the server.
1.35 June 27, 1997 Fixes a minor bug in the edge triples identification. Improves the
data sent to the statistics server. As a courtesy to the user, all
data transmitted from his client to the server is echoed in the
Java Console. Compiliation with the optimization switch results
in 6198 bytes reduction in the size of class files but gives a
6% increase in run time for the SC-shaped part.
1.36 July 12, 1997 Adds error trapping for the NullPointer error in F2DStatClient
connection in init() that would occur for the OS2 Netscape 3.0
client behind the IBM firewall in Zurich. Adds an option <param
"ClampType"> to draw a bullet clamp representation.
1.39 Sep. 1, 1997 Shortens the clamp symbol to reduce apparent part interferences.
Adds the "4-unit Right Triangle" stock part. Adds a parameter
option to have the fixture set sorted on "closeness to orientation"
which is set in the html code.
2.00 Jan. 12, 2001 After four years of operation, some new enhancements are in work.
2.01 Jan. 13, 2001 Implements a variable clamp length (coded as an instance variable
definition. The implementation is for a symbolic clamp (bullet shape)
only. We don't know what a real clamp actually looks like. Attempting
to code for every conceivable clamp shape is impossible. Approximately
3 hours programming time.
2.04 Jan. 15, 2001 Implemented filtering for clamp interference, in two parts. The first
filters for interference with the part, the second filters for
interference with the locators. Fixes the duplicate locator triple
bug. Approximately 9 hours programming time.
2.05 Jan. 16, 2001 Implements double buffering for the fixture display area (FDA).
Changes the way the "respect vertices" parameter option works
(offending configurations are filtered out completely instead of
having their quality metrics divided by a thousand). Approximately
4 hours programming time.
2.07 Jan. 17, 2001 Implements reaction force display for computed fixtures. Approximately
8 hours programming time.
Charles Anderson at Berkeley did the first successful Java user interface as a front end to my fixture server (see FixtureNet II). The fixture server was also the engine behind the original FixtureNet. Experience using Charles' excellent implementation, and Charles' helpful comments, influenced my design.
You may use these classes for academic research or educational purposes. If you use these classes, or any classes derived from the source code, you must attach appropriate attribution to source files and the program user interface. A link to my home page will also be appreciated.
Comments? Please send
E-mail to Rick Wagner (rwagner@teamster.usc.edu).
Visit my
USC home
page.
This page established June 10, 1997; last updated January 18, 2001.