Three-Dimensional ConceptsChapter 9Three Dimensional GraphicsItisthefeldofcomputergraphics thatdealswithgeneratingand displayingthreedimensionalobjects inatwo-dimensionalspace(eg display screen!Inadditiontocolorandbrightness"a #-D pi$els adds a depth property that indicateswherethepointliesonthe imaginary %-a$is&'hen many #-D pi$els are combined" each with its own depth (alue" the result is a #-D surface called a te$ture&)bjectsarecreatedona#-Dstage wherethecurrent(iewisderi(ed fromthecameraandlightsources" similar to the real world&Coordinate Reference This coordinate reference defnes the position and orientation for the plane of the camera flm.Three-Dimensional CoordinatesxyzxyzRight handed Left handedThree-Dimensional Display Methods *Parallel projection *+roject points on the object surface along parallel lines onto the display plane&*+arallel lines are still parallel after projection&*,sed in engineering and architectural drawings& -yselectingdi.erent(iewingpositions" we can project (isible points on the object ontothedisplayplanetoobtaindi.erent two-dimensional (iews of the object&Top ViewSide ViewFront ViewThree-Dimensional Display Methods * Perspective projection * Project points to the display plane along converging paths. * This is the way that our eyes and a camera lens form images and so the displays are more realistic.It has two major characteristics/maller as their distance from the obser(er increases&0oreshortenedthesi%eofanobject1s dimensionalongthelineofsightare relati(elyshorterthandimensions across the line of sight&Three-Dimensional Display Methods* Depth cueing * dentify which is the front and which is the !ac" of displayed o!jects * #or wireframe displays $ary the intensity of o!jects according to their distance from viewing position * #or the atomsphereThree-Dimensional Display Methods Depth Cueing To easily identify the front and !ac" of display o!jects. Depth information can !e included using various methods. % simple method to vary the intensity of o!jects according to their distance from the viewing position. &g' lines closest to the viewing position are displayed with the highest intensities and lines farther away are displayed with decreasing intensities. 2pplicationismodelingthee.ectoftheatmosphereonthepi$el intensityofobjects&3oredistantobjectsappeardimmertous thannearerobjectsduetolightscatteringbydustparticles" smo4e etc&Three-Dimensional Display Methods* $isi!le line and surface identifcation * (ighlight the visi!le lines or display them in di)erent color * Display nonvisi!le lines as dashed lines * Remove the nonvisi!le linesThree-Dimensional Display Methods* *urface rendering * *et the surface intensity of o!jects according to +ighting conditions in the scene %ssigned surface characteristics 5ightingspecifcationsincludetheintensityandpositionsoflight sourcesandthegeneralbac4groundilluminationre6uiredfora scene& /urface properties include degree of transparency and how rough or smooth the surfaces are to be&Three-Dimensional Display Methods 7$ploded and Cutaway 8iews To maintain a hierarchical structures to include internal details& These (iews show the internal structure and relationships of the object partsThree-Dimensional Display Methods* Cutaway view * Remove part of the visi!le surfaces to show internal structure. Three-dimensional and stereoscopic views