Orf-UnidataSummer2006-tutorial

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• Publié par: Vewyir
• Nombre de lectures: 17
• Langue: Español

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Vis5dasa3DNumericalModelDataInterrogationTool
LeighOrf,CentralMichiganUniversity
Background
Vis5disaninteractivedatavisualizationandinterrogationprogram. The‘5’in‘Vis5d’refersto
fivedimensions: threespatialdimensions,time,andvariables;multiplevariablescanbe
visualizedsimultaneously.
Any3DdatacanbevisualizedwithVis5dalthoughitwasdesignedtovisualizegridded
numericalmodeldata. Ifyoucangetyourdatainto3Dfloatingpointarrays,youcanvisualize
itwithVis5d.
Vis5dwasdevelopedatSSECbyBillHibbard,nowretired,anddevelopmentontheoriginal
Vis5dcodehasceased. However,BillreleasedthesourcecodeofVis5d5.2undertheGPL,and
acommunity drivenversionofVis5dnowexistscalledVis5d+. However,developmenton
Vis5d+hasnotoccurredsince2002. AVis5dmailinglistexistswhichmayassistyouinany
Vis5dproblemsyoumayencounter(Googleisyourfriend).
TheversionofVis5dyouareusinginthisworkshopisVis5d+ 1.3.0beta. Thisversioncontains
somefeaturesandimprovementsoverVis5d5.2butthecodeisperhapsnotasstable. Either
versionwillsufficeforcasualuse.
HowdoIgetmydataintoVis5d?
CreatingVis5dfilesisprettystraightforwardanddocumentationexistsonhowtodothis. I
wouldrecommendthedocfilesintheVis5d+distributionforguidanceonthis. Therearesome
communitymodelswhichhaveaVis5doutputoptionandsomeexistingprogramstoconvert
filestoVis5dformat.
IfyouarelookingtocreateyourownVis5dfilesfromyourowndata,theVis5dAPIincludes
thefollowingcallsyouwillneedtoexamine:
v5dCreateandv5dCreateSimple-createaVis5dfile
v5dWrite-write3DdatatotheVis5dfile
v5dClose-closetheVis5dfile.
YoucancallthesefromeitherCorFORTRAN.Exampleprogramsareinthedocumentation.
Vis5drunsunderUnix/Linux. AversionforWindowsdoesnotexistasfarasIknow. Vis5d
willrununderMacOSXifyoufirstinstallthedevelopertools.
StartingVis5d
Ifyousimplytype
% vis5d
alonglistofoptionswillbepresentedtoyou. Normally,allyouneedtopasstovis5disthe
nameofyourexistingvis5dfile,i.e.:
1% vis5d wkshp_2hr.v5d
willopenthefirstfilewewillbeexamininginthisworkshop.
UsingVis5d
Ourdatasetforthisworkshopisfromanumericalsimulationofasupercellthunderstorm. We
willbeexaminingvectorandscalarquantitiesaswellasobservingwindtrajectories.
1. Startwiththefilewkshp 2hr.v5d. Whenyoufirststartvis5d,youarepresentedwitha
panelontheleft,containingmanybuttons,andtheboxontherightcontainingthe
visualization.
Placethecursorintheviswindowandclickandholdtheleftmousebutton. Movethe
mouseandobservehowthecuberesponds. Dothesamewiththemiddleandrightbuttons. Getusedtomanipulatingthecube. Note: forthoseofyouusedtoIDV,
theVis5dcuberespondsdifferentlytotheIDVcube! Thiscanbeenoughtomakeyour
headexplode. Asalong timeVis5duserIhaveahardtimegettingusedtotheIDVway,
whichIbelieveisbaseduponVisAD,whichwasalsowrittenbyBillHibbard.
Torestorethecubetoitsoriginalposition,clickontheTOPbuttonneartheupperleft
handcornerofthepanel. SOUTHandWESTdowhatyouwouldexpect. Right clicking
onthesewillgiveyouthe180degrees oppositeview.
PerhapsonethemostpowerfulfeaturesofVis5disitsabilitytorenderisosurfaces
quickly. Isosurfacescanbethoughofasthree dimensionalcontours. Allalongan
isosurface,valuesofaquantityareconstant. Valuesinsideanisosurfaceareeitherlarger
thanorsmallerthanthevalueoftheisosurface.
2. Selectqcqi(cloudwater+iceing/kg)intheIsosurfcolumninthelowerpartofthepanel
beneaththecolumnofbuttons. Thewidgetwhichpopsupcontainsasliderwitharange
fromtheminimumvaluefoundinthedatatothemaximum. Slidethesliderovertoa
valueof0.2g/kgandclickOK.Examinetheisosurfacemanipulatingthecube.
3. Now,Idon’tknowaboutyoubutIthinkthatisoneugly coloredcloud. Let’smakeit
white. Ifyouright clickontheqcqiIsosurfacewidget,acontrolpanelcomesupwithRGB
sliders. Ifyoumovethemallovertotherightyou’llhaveawhitecloud.
4. TryslidingtheOpacityslidertotheleftandseewhathappens. Transparentisosurfaces
areusefulwhenyouhavestuffgoingoninsideanisosurface.
5. Tryexperimentingwithdifferentvaluesofqcqi.
6. De selectqcqi(cloudgoesaway)andlet’sfindthesupercellupdraft. Chooseavalue
around35m/sforW.Now,bringbackthecloudbutmakeittransparent. Youshouldbe
abletoseetherelationshipbetweentheclouditselfandtheupdraftinsidethecloud.
7. Bynowyouareprobablygettingthehangofisosurfaces. Trylookingatreflectivity(dbz)
andverticalvorticity(zeta). Youshouldbeabletofindaveryprominentweakecho
2regionlookingatdbz,alongwithsomeinterestinglookingregionsofverticalvorticity.
Thestructureofthecoldpoolisevidentchoosingavalueofabout307KforTheta.
8. Vis5dcanrender3Dwindvectors. SelectHwind1(locatedabovetheIsosurfbuttonsyou
havebeenplayingwith). Dragtheplanedowntothesurfacetoexaminethe
storm relativesurfacewinds. Youmaywishtozoominastherearealotofvectors.
9. IntheHWindwidget,changethevalueoftheHWind1Scaletosomethingsmaller,say
0.5. PressEnterormovethecursoroutoftheboxforthechangetotakeeffect. Youcando
thesameforvectordensity;ifyouwishtoremoveeveryothervector,putavalueof0.5in
theDensitybox.
10. Youcanlookatverticalcrosssectionsofwindvectorsinthesameway(clickonVwind1).
However,tomovetheverticalslice,youneedtochangethecontextofthemouse
functionsfromNormal(currentlyselected)toSlice. Youcannowdragaslicearoundby
selectingitscornerswiththerightmousebuttonorthetabinthetop/bottomcenterofthe
slice. RemembertochangeyourcontextbacktoNormalonceyouaredonemanipulating
theslice.
Other2Dslicesareavailabletoview: ”ContourSliceHoriz.””ContourSliceVert.”
”ColoredSliceHoriz.””ColoredSliceVert.”alldowhatyouwouldexpect.
11. Let’slookatacoloredsliceofsurfacepotentialtemperature(Theta). Sincepotential
temperaturehassuchalargerangebutalongahorizontalplaneitsrangeissmall,we
needtomanipulatethedefaultcolormapinordertoseevariationsinpotentiale.
Placeyourcursorabovethecolormap(withtheRGBcurves)andusetheleft,center,and
rightarrowkeyboardkeystomanipulatethecolormaptoyourliking. Youshouldbeable
toclearlydelineatethecoldpoolbydoingthis.
12. QuitVis5dandlet’slookatthesecondfile: wkshp 60.v5d. Thisfilecontainsasequenceof
modelstates(separatedin1minuteintervals)andcanbeanimated.
Note: Whenyouselectanisosurface,slice,etc.,whenviewingafilecontainingseveral
timelevels,Vis5dmayloadallofthetimelevelsintomemoryanddotherendering
immediately. Itisbesttowaitforeverythingtoload(asindicatedbythehourglassor
”waitasec”cursor)beforemanipulatingthecubeinthiscase. Ifyouwouldpreferthat
Vis5donlyrenderthecurrentframeofafilecontainingseveralframes,youcanpassthe
verylarge1optiontovis5d,i.e.:
% vis5d wkshp_60.v5d verylarge 1
Nowthatyouareexaminingafilewithasequenceofmodelstateswhichcanbe
animated,youmayalsoexaminethebehavioroftrajectories.
13. Stopthemodelstateatframe25of36asisindicatedinthetopleftcornerofthevispanel
(containingtheclock).
314. SelecttheTrajectorycontextwidget. ClickontheRibbonbuttonandchangethevalueof
Lengthto15.
15. The3Dcrosshairscanbemovedaroundbyright clicking. Onceyouaresatisfiedwithits
location,middleclickONCEtodropatrajectory. Vis5dwillchurnawayforawhileasit
calculatesthetrajectorylocationbaseduponthethreecomponentsofwind. Thetrajectory
ribbonwillappearoncethecalculationiscomplete.
16. Interestingplacestoputtrajectoriesinclude: Theupdraftatmidlevels. Therearflank
downdraft(RFD)neartheground. TrydroppingafewtrajectoriesfromSet1inthe
updraft,andafewfromSet2intheRFD.Animateit.
FinalNotes
Vis5disapowerfultoolwhichcanbeusedtogivestudentsandresearcherstheabilityto
interactivelyexamine3Dmodeldataandseewhatisgoingoninafullythree dimensional
context. ThislabhasonlyshowcasedsomeofVis5d’sfunctionality. Inmyexperience,
undergraduatestaketoitveryquicklyandfindittobeaveryeducationalexperience. With
communitymodelssuchasWRF,ARPS,RAMSetc. availabletouniversities,anyonecancreate
theirownsimulationsrunningonconsumerhardwareandmakeVis5dfiles. Goodluck,and
havefun!
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