美国人的汽车画法(1)

外国人的汽车画法DrawingEllipsesAnatomyofanellipse:Whenweviewacircleatanangleweseeanellipse.Werefertothisviewingangleasthedegreeoftheellipse.Aperfectcircleisviewedat90degreesandatangleslessthanthatweseevariousdegreeellipsesonthewaydowntoazerodegreeellipse(astraightline).Understandingthemechanicsofdrawingellipsesisnotdifficult,masteringthedrawingofellipsesis.Anellipsehastwoaxesweneedtoknowabout,theminoraxisandthemajoraxis.Theminoraxisdividestheellipseintotwoequalhalvesacrossitsnarrowdimension.Themajoraxisdividestheellipseacrossitslongdimensionintotwoequalhalves.Theminorandmajoraxescrosseachotherata90degreeangle.Seedrawinge-1.Ifwelookatthedrawingine-2wecanseethatIhavedrawnasquarearoundourellipse.AfterIdrawthesquareIdrawan“X”acrossittofinditscenterinperspective.Whenyouobservetheminorandmajoraxesoftheellipseweseethattheminoraxisgoesthroughthecenterofthesquarewhilethemajoraxisdoesnot.Wealsoobservethattheellipsetouchestangentexactlyinthemiddleofeachsideofthesquare,exactlywherewewouldexpectitto.Thisisabitofamindbender.Wehavetakenasymmetricalshape,theellipse,anddroppeditintoperspective.Thisalwaysworksifyoudoyourdrawingwithintheallowablelimitsofdistortion.Regardlessofwhetheryourellipseisrollingonthegroundorrestingonit,asweseeindrawinge-3,theconstructionresultremainsthesame.Learningfromthisobservationandnowknowingwheretheminorandmajoraxesofourellipseshouldbeisthesinglegreatesthelpindrawingellipsesproperly.Sincetheellipseminoraxisalwaysgoesthroughthecenterofoursquarethisissomethingwecanusetohelpusdrawit.Converselythemajoraxisreferencesnothingthatcanhelpusinlocatingitinourperspectivesquare.ThisiswhyIdonotrecommendusingthemajoraxiswhendrawingellipses.Practicedrawingellipseswithoutworryingaboutlocatingtheminperspective.Hereareafewexamplesofmyrustyarmtryingtodrawsomeellipsesforthistutorialthismorning.Drawvarioussizesanddifferingdegrees.Afteryoudrawtheellipseidentifyitsminoraxisbydrawingalineacrossitsnarrowdimensionthatdivideseachsideequally.findithelpfulifyouimaginethatyouaregoingtofoldyourellipsealongthisline.Youwantittofoldalongthislineandlandexactlybackonitself.Ifyourminoraxisisincorrectwecanseewhathappensindrawinge-4.Afteryouarefeelinggoodabouthowyourellipsesarelookingandyouareconfidentyoucanlocatetheminoraxisofeachproperlyyouarereadytostarttryingtolocateyourellipseswithinperspectiveconstructions.Startwithsomethingsimplelikedrawingastraightlinethatrepresentstheminoraxisofyourellipseandthentryanddrawellipsesofvarioussizesanddegreesonthatline.Thisisalittleharderthandrawingtheellipsefirstandthendrawingtheminoraxis.Afteryounailthatexercisetrydrawingtwoconvergingstraightlinesanddrawingellipsesthattouchtangenttoeachline.Thisisharderstill.Oneofthemostdifficultexercisesistodrawapageofcubesandthendrawanellipseoneachfacethattouchestangenttothesideofeachsquareasweobservedindrawingse-2ande-3.Drawingconcentricellipsesarealsogoodpractice.Youcanuseellipseguidestostraightenupyourellipsesbutdonottrytosketchwiththem.Ihaveyettoseethisdoneefficiently.Youaremuchbetterofftodoallofyourperspectivelayoutworkfreehandandthenbreakoutthesweepsandellipseguidestotightenthingsupifyouneedto.Onceyouhavepracticedenoughyouwillfindthatyoucandoverycompetentdrawingsentirelyfreehand.Thereisagreatsenseofsatisfactionthatcomesfromachievingnicelinequalityandproperperspectiveinafreehandsketch.Howtocheckifyourellipseiscorrectlydrawn.Itisimportanttounderstandthemechanicsofellipsessoyoucanmakeadjustmentstothemafteryouhavedrawnthem.Basicallythereareonlytwothingsthatmakeanellipseeitherproperlydrawninperspectiveornot.Minoraxisandyourvanishingpoints.Thefirstthingtocheckiswhetheryourminoraxisiscorrect.Inthecaseofputtingwheelsoncarstheminoraxisisalwayscommontotheaxleofthewheel.Mostofthetimethisaxleisalsoperpendiculartothecenterlineofyourcar.Soitfollowsthattheminoraxesofyourellipses(wheels)arealsoperpendiculartothiscenterline.Therearecasessuchaswhenthefrontwheelsareturnedorthewheelshavebeensetupwithextremecamberthattheyarenolongerperpendiculartothecenterlineofyourvehicle.Anothereasyexampleforustovisualizeisthattheminoraxisofapropelleronanairplaneisparalleltothecenterlineofthefuselageandthereforetheygotothesamevanishingpoint.Rememberwhenperspectivedrawingthat“allparallellinesgotothesamevanishingpoint”.Degreeofyourellipse.Assumingtheminoraxisofyourellipseiscorrectandyourellipsestilllookswrongitcanbeonlyonething,thedegree.Beforetryingtoadjustthedegreeofanellipsetheminoraxismustbecorrect.Noamountofadjustmenttothedegreecanmakeupforanincorrectminoraxis.Checkingthedegreeisasimpleperspectiveconstruction.Step1:Drawaboxaroundandtangentoneachsidetoyourellipse.Besuretofollowyourperspectiveguidelineswhendoingthis.Step2:Observewhereyourdrawnellipsecontactstheboxyouhavedrawnaroundit.Ifyourellipsedoesnottouchinthemiddleofeachsideoftheboxthenthedegreeiswrong.Adjustthedegreeofyourellipsebymakingitwiderornarroweruntilyoucandrawaboxarounditthattouchesexactlyinthemiddleofeachside.Whenyouhavedonethisyouwillhaveaproperlydrawnellipseatthecorrectdegree.HereareafewmoresketchesIquicklyputperspectiveguidelin