Table Of Content

AD-A248 167 11111111Ii1Il!1l11 1l10'1'i11 1i ~~~ ~ ~OF DTIC Li,119 ____ ____ ___ "rn"tcuny %.at"i APRLEC199 for High-Speed Volume Rendering THESIS 0 Patricia L. Brightbill Captain AFIT/GCSIENG/92M-OI 92-08126 DEPARTMENT OF THE AIR FORCE AIR UNIVERSITY AIR FORCE INSTITUTE OF TECHNOLOGY Wright-Patterson Air Force Base, Ohio 92 331 085. AFIT/GCS/ENG/92M-O 1 Distributed Ray Casting for High-Speed Volume Rendering THESIS Patricia L. Brightbill Captain AFIT/GCSENG/92M-O1 approved for public release; distribution unlimited jan1~9u9a y '-%1asters Thesis N7 L Aa,0 5S 3 : L Distributed Ray Castin- for Hig-h-Sp~eed Volume Rendering Patricia L. BrighLbill, Capt. USAF Air Force Institute of Technology, WPAFB OH 45433-6583 .AFIT/GCS,/ENG,'92M-0D1 3. -~.~-uau:I CNiTC~siNG AGENC! NAME.3* * A4sC RAZ5 14 ?CC.'N- ,2: "a. LIS-MIIUTIO~ AjA.LAS1L,' -j, ,7ME'PT 7: 1T3 :Cd'j Cs'Z Approvedl 'or public release; distribution unlimited Tile volume rendering, technique known as ray casting or ray tracing is notoriously slowv for large volume sizes. ye 'rvdesusp erior images. A technique is needed to accelerate ray tracing volumes Without depending on special purpose or parallel computers. The realization and improvements in distributed computing over the past two decades has motivated its use in this work. This thesis explores a technique to speedup ray casting by distributed programming. The work investigates the possibility of dividing the volume among general purpose workstations and casting rays (using Levoy's front-to-back algorithm) through each subvolume independently. The final step being the composition of all subvolume rendered images. Results indicate a 7.5 percent savings in rendering time by distribu ted processing over eight processors versus a single processor. ( :iputrn m. [:.i.I hiv I I' dl Biv (I;L-rinoDI-trb al 1, 11,1' .\SlTlI 7 NIASFIKIL\~~~IDI AFIT/GCS/ENG/92M-01 Distributed Ray Casting for High-Speed Volume Rendering THESIS Presented to the Faculty of the School of Engineering of the Air Force Institute of Technology Air University In Partial Fulfillment of the Requirements for the Degree of Master of Science in Computer Systems Patricia L. Brightbill, B.S. in Computer Science Captain, USAF Acession For NTIS T- A&I January, 1992 DTi T:7 E Av ' " Approved for public release; distribution unlimited . Dist . Implementation. .............................................................................................. 3-1 Volume Renderer ................................................................................................... 3-1 Design ............................................................................................................ 3-1 Implementation. .............................................................................................. 3-5 Distributed ............................................................................................................. 3-8 Analysis .......................................................................................................... 3-8 Approach ........................................................................................................ 3-8 Design ............................................................................................................ 3-8 Implementation ............................................................................................. 3-11 Sum m ary .............................................................................................................. 3-14 IV.R esults ..................................................................................................................... 4-1 Overview ............................................................................................................... 4-1 Test Volume Data and Output ................................................................................ 4-1 Im ages .................................................................................................................... 4-2 CT Volumes ..................................................................................................... 4-2 Artificial Box Volume ..................................................................................... 4-2 Tim ing .................................................................................................................... 4-8 CT Chest Volume ............................................................................................ 4-8 Artificial Box Volume ..................................................................................... 4-9 Sum m ary ................................................................................................................ 4-9 V. Conclusions and Recom me ndations ........................................................... 5-1 Conclusions ............................................................................................................ 5-1 Recommendations .......................................................................................... 5-2 Volume Renderer ..................................... ... 5-2 iff Table of Contents Figures ................................................................................... Tables .................................................................................... vii Acknowledgements.................................................................. viii Abstract .................................................................................. ix 1.I ntroduction.......................................................................... 1-1 Background.............................................................................. 1-1 Problem ................................................................................. 1-2 Assumptions/Materials and Equipment............................................... 1-3 Scope and Limitations.................................................................. 1-3 Approach/Methodology ................................................................ 1-4 Thesis Overview ........................................................................ 1-4 1I. Literature Review ................................................................. 2-1 Overview ................................................................................ 2-1 Volume Rendering...................................................................... 2-1 Speedup Techniques.................................................................... 2-2 Ray Tracing Speedup.............................................................. 2-2 Related Speedup ................................................................... 2-4 Distributed Computing................................................................. 2-5 Conclusions ............................................................................. 2-6 Summary................................................................................. 2-6 Ill. Design and Implementation................................................... 3-1 Overview ................................................................................ 3-1 Design.............................................................................. 3-1 Hi Distributed. ........................................................................ 5-3 Appendix DVR Operations Manual .............................................. A-i Bibliography......................................................................... BIB-i Vita.................................................................................... VITA-i iv Figures Figure2 .1 Shading and ClassificationP ipeline .............................................................. 2-2 F igure 2.2 Ray Casting .................................................................................................... 2-3 Figure3 .1 Volume Renderer Top Level DFD. .................................................................. 3-2 Figure3 .2 Overview of Volume Rendering Algorithm ..................................................... 3-3 Figure3 .3 Volume Renderer Class Diagram. .................................................................. 3-4 Figure3 .4 OrthographicP rojection. ......................................................................... 3-5 Figure3 .5 Volume Renderer Pipeline. ............................................................................. 3-6 Figure3 .6 Octant Subdivision ......................................................................................... 3-9 Figure3 .7 DistributedT op Level DFD ............................................................................ 3-9 Figure3 .8 DistributedL evel I DFD. ........................................................................ 3-10 Figure 3.9 DistributedC lient Class Diagram. ............................................................... 3-11 Figure 3.10 Client-Server Message Passing. ................................................................. 3-13 Figure 3.11 Padded Octant ............................................................................................ 3-14 Figure4 .1 CT Chest Volume Rendered by Single Processor( left) and Distributed P rocessors (right) ............................................................................................................. 4-3 Figure4 .2 CT Chest Volume Rendered by Single Processor( left) and Distributed P rocessors (right) ............................................................................................................. 4-3 Figure 4.3 Rotated Views of CT Chest Volume Rendered by DistributedP rocessors.. .... 4-4 Figure 4.4 Cut-Away Views of CT Dog Heart Volume Rendered by Distributed P rocessors. ........................................................................................................................ 4-4 Figure4 .5 CT Chest DistributedV olume Rendering of Octants ...................................... 4-5 Figure4 .6 Artificial Box Volume Rendered by Single Processor( left) and Distributed Processors( right). Top and Side View .............................................................................. 4-6 Figure4 .7 Artificial Box Volume Rendered by Single Processor( left) and Distributed Processors( right). Isometric Views .................................................................................. 4-6 V Figure4 .8 Artificial Box DistributedV olume Rendering of Octants ............................... 4-7 Figure4 .9 Comparison of CPU Clock Times (in Microseconds)fort he Preprocessing Step of Volume Renderer Between Single Processor( Black) and Distributed( Hashed) Implementations on CT Chest Data. ............................................................................... 4-11 Figure4 .10 Comparison of CPU Clock Times (in Microseconds)f or the Ray Casting Step of Volume RendererB etween Single Processor( Black) and Distributed( Hashed) Implementations on CT Chest Data. ............................................................................... 4-11 Figure4 .11 Comparisono f CPU Clock Times (in Microseconds)for the Total oj Preprocessinga nd Ray Casting Steps of Volume Renderer Between Single Processor (Black) and Distributed( Hashed) Implementations on CT Chest Data. ........................ 4-12 Figure 4.12 Comparison of Average CPU Clock Times (in Microseconds)forA ll Runs by Steps and Total on CT Chest Da ta .................................................................................. 4-12 Figure 4.13 Comparisono f CPU Clock Times (in Microseconds)for the Preprocessing Step of Volume Renderer Between Single Processor( Black) and Distributed (Hashed) Implementations on Artificial Box Data ......................................................................... 4-14 Figure 4.14 Comparison of CPU Clock Times (in Microseconds)f or the Ray Casting Step of Volume Renderer Between Single Processor( Black) and Distributed( Hashed) Implementations on Artificial Box Data. ........................................................................ 4-14 Figure 4.15 Comparison of CPU Clock Times (in Microseconds)for the Total of Preprocessinga nd Ray Casting Steps of Volume Renderer Between Single Processor (Black) and Distributed (Hashed)I mplementations on Artificial Box Data .................. 4-15 Figure 4.16 Comparison of Average CPU Clock Times (in Microseconds)f or the Steps and Total on Artificial Box Data. .................................................................................... 4-15 vi Tables Table 4.1 Table of CPU Clock Times (in Microseconds)f or Single Processora nd DistributedI mplementations of Volume Renderer Shown by Steps and Total as Executed by View of C T Chest Da ta. .............................................................................................. 4-10 Table 42 Table of CPU Clock Times (in Microseconds)f or Single Pf cessor and DistributedI mplementations of Volume Renderer Shown by Steps and Total as Executed by View of Artificial Box D ata ........................................................................................ 4-13 Table A.) DVR Server Control File Format. ............................................................... A-1 Table A.2 DVR Modified GPR Control File Format. ................................................. A-2 Table A.3 DVR Volume Control File Format .................................................................. A-3 vii