基于软硬件协同设计的实时并行体绘制研究
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摘要
体绘制技术是三维数据场可视化技术的一个重要分支,在医学、地质勘探、流体力学等领域均有广泛应用。研究者们提出了多种体绘制算法,其中光线投射算法是现有体绘制算法中图像效果较好的一种,但是由于投射光线数据量巨大,对每条光线又需多次采样,导致生成图像的速度较慢。
目前体绘制方法的实现主要有两种：软件实现和硬件实现。软件实现在体绘制中应用得十分广泛,但绘制的体数据往往比较庞大,只依靠软件加速绘制尤其是绘制具有整体光照效果的图像时,算法性能还是有限的。因此人们将目光转向图形硬件,希望借助硬件提供的相关功能加速体绘制。虽然目前的这些专用体绘制硬件系统能够达到一定规模数据场实时体绘制的要求,且算法流水线根据硬件结构经过了最优处理,实时绘制性能得到提高,但算法的流程固定不变,其灵活性相对比较差,而且对硬件配置要求很高,价格昂贵。
本文采用可配置的FPGA解决方案,提出了一种基于软硬件协同设计的高效并行光线投射算法框架,把计算复杂但计算量少的任务和人机交互的任务通过软件实现,而那些计算简单且计算密集型的任务通过硬件并行实现。这样既提高了绘制速度,又兼具友好的交互性,具有更好实用性。直方图引导的自适应局部传递函数方案的提出保证了高质量图像的生成,而且增强了图像的细节信息。算法框架的提出使便携式小型化的诊断系统的实现成为可能。
Volume rendering is a significant part of 3D data visualization, is widely used in medicine, geological survey, hydrodynamics, and so on. Researchers propose several volume rendering algorithms, in which Ray Casting is more efficient, but enormous rays and sampling lead to longer time.
From now on, there are mainly two implementations of volume rendering, one is software implementation, the other is hardware implementation. Software implementation is widely used in volume rendering, but enormous volume data results in worse performance. Thereafter researchers tend to graphic hardware to improve rendering performance. These special hardware rendering systems can achieve real-time requirement, and algorithm pipelines can be optimized, yet algorithm flow is fixed, the flexibility is bad, requirement of hardware configuration is great, and the price is expensive.
This paper uses configurable FPGA resolution, and proposes an efficient parallel Ray Casting based on hardware/software co-design, which implements complicated but less computational jobs and Human-Computer interaction by software, and implements simple but computation-intensive jobs parallel by hardware. Thus rendering speed is improved, and it has good HC interaction and practicability. Proposal of histogram guided adaptive local transfer function can improve the quality of rendering image and enhance details of image. The proposal of algorithm framework makes implementation of portable mini diagnose system possible.
目前体绘制方法的实现主要有两种：软件实现和硬件实现。软件实现在体绘制中应用得十分广泛,但绘制的体数据往往比较庞大,只依靠软件加速绘制尤其是绘制具有整体光照效果的图像时,算法性能还是有限的。因此人们将目光转向图形硬件,希望借助硬件提供的相关功能加速体绘制。虽然目前的这些专用体绘制硬件系统能够达到一定规模数据场实时体绘制的要求,且算法流水线根据硬件结构经过了最优处理,实时绘制性能得到提高,但算法的流程固定不变,其灵活性相对比较差,而且对硬件配置要求很高,价格昂贵。
本文采用可配置的FPGA解决方案,提出了一种基于软硬件协同设计的高效并行光线投射算法框架,把计算复杂但计算量少的任务和人机交互的任务通过软件实现,而那些计算简单且计算密集型的任务通过硬件并行实现。这样既提高了绘制速度,又兼具友好的交互性,具有更好实用性。直方图引导的自适应局部传递函数方案的提出保证了高质量图像的生成,而且增强了图像的细节信息。算法框架的提出使便携式小型化的诊断系统的实现成为可能。
Volume rendering is a significant part of 3D data visualization, is widely used in medicine, geological survey, hydrodynamics, and so on. Researchers propose several volume rendering algorithms, in which Ray Casting is more efficient, but enormous rays and sampling lead to longer time.
From now on, there are mainly two implementations of volume rendering, one is software implementation, the other is hardware implementation. Software implementation is widely used in volume rendering, but enormous volume data results in worse performance. Thereafter researchers tend to graphic hardware to improve rendering performance. These special hardware rendering systems can achieve real-time requirement, and algorithm pipelines can be optimized, yet algorithm flow is fixed, the flexibility is bad, requirement of hardware configuration is great, and the price is expensive.
This paper uses configurable FPGA resolution, and proposes an efficient parallel Ray Casting based on hardware/software co-design, which implements complicated but less computational jobs and Human-Computer interaction by software, and implements simple but computation-intensive jobs parallel by hardware. Thus rendering speed is improved, and it has good HC interaction and practicability. Proposal of histogram guided adaptive local transfer function can improve the quality of rendering image and enhance details of image. The proposal of algorithm framework makes implementation of portable mini diagnose system possible.
引文
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[49]G. Kinttel. VERVE:Voxel Engine for Real-Time Visualization and Examination. Computer Graphics Forum, 19(3):37-48, September 1993.
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[55]Lacroute P, Levoy M.1994, Fast Volume Rendering Using a Shear-Warp Factorization of the Viewing Transformation.Computer Graphics, Proceedings, July,451～458
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[2]Rezk-Salama C, Engel K. Bauer M. et al. Interactive volume rendering on standard PC graphics hardware using multi-textures and multi-stage-rasterization. Eurographics/SIGGRAPH Workshop on Graphics Hardwar'00. 2000.109-118.
[3]彭延军,石教英,体绘制技术在医学可视化中的新发展,中国图像图形学报,2002.12
[4]Levoy M. Volume Rendering by Adaptive Refinement. Visual Computer.1990,6(1):2-7
[5]Cheng L, Yu C. An efficient volume-rendering algorithm with an analytic approach, The Visual Computer,1996.515-526
[6]Jung A, Sung M, Jong B. Efficient Multi Resolution Volume Rendering scheme. Image Display and Visualization. SHE Press,2000:134-140
[7]Milos S. Fast Surface Rendering From Raster Data by Voxel Traversal using Chessboard Distance. Proceedings of Visualization'94,1994.188-195
[8]Yagel R. Shi Z. Accelerate Volume Animmion by Space Leaping. IEEE Visulization'93:IEEE Computer Society Press.1993,166-168
[9]Levoy M. Efficient Ray Tracing for Volume Data. Computer Graphics,1990,9(3):245-261
[10]Agate M, Grinsd L. The HERO Algorithm for Ray Tracing Octrees. Advance in Computer Graphics Hardware,1997,12(3):61-73
[11]Glassner A. Space Subdivision for Fast Ray Tracing. IEEE CG&A,1984,4(1):15-22
[12]Wihelms J, Golder A. Octrees for Faster Isosurface Generation. Computer Graphics,1998,11(3):134-145
[13]Sungup C, Hngeongdo K. Efficient Space Leaping Method for Volume Rendering. Medical Imaging 1999, SHE Conference on Visual Data Exploration and Analysis, Munich:SPIE Press,1999:263-270
[14]Etrl T, Westermann R, Grsso R. Multi Resolution and Hierarchical Methods for the Visualization of Volume Data. Future Generation Computer System,1999,15(1):31-42
[15]Kim T Y, Shin YG. An Efficient Wavelet-based Compression Method for Volume Rendering. Computer Graphics and Applications, Proceedings 7th Pacific Conference Singapore:IEEE Computer Society Press,1999: 147-156
[16]Michel A W, Jos B T. X-ray Volume Rendering by Hierarchical Wavelet Splatting. Pattern Recognition, Proceedings,15th International Conference. Washington:IEEE Computer Society Press.2000:P.159-163
[17]Pfister H., Kaufman A. and Chiuch T., Cube-3:A Real-Time Architecture for High-Resolution Volume Visualization. Proceeding of 1994 Symposium on Volume Visualization. Wrashington D.C.994:75-82
[18]Pfister H...Kaufman A.. Cube-4:A Scalable Architecture for Real-Time Volume Rendering, Proceeding of 1996 Symposium on Volume Visualization, San Francisco, C.A. Oct.,1996:P.47-54
[19]Kreeger, K. and Kaufman A, Hybrid Volume and Polygon Pendering with Cube hardware. Proceedings of the ACM SiGGRAPH/EUROGRAPHICS workshop on Graphics hardware.1999:15-24
[20]Knittel, G, A Compact Volume Rendering Accelerator. Proceedings of 1994 Symposium on Volume Visualization,1994:67-74
[21]Pfister, H., etal. The VolumePro Real-time Ray-casting System. Proceedings of the 26th annual conference on Computer graphics and interactive techniques 1999. Los Angeles. CA. USA
[22]Knittel. G and W.Strasser, Vizard-Visualization Accelerator for Realtime Display. Proceedings of the ACM SIGGRAPH/EUROGRAPHICS workshop on Graphics hardware 1997:139-146
[23]T Gunther, C Poliwoda, C Reinhart,, J Hesser. A Massively Parallel Processor for Realtime Volume Visualization in Medicine. Proc. Euro graphics Workshop. Oslo, Norway,1994:103-108
[24]夏放怀,沈振康等,一种用于实时体绘制系统的自适应采样算法,电子学报,2002.3
[35]Cullip, T. J., Accelerating Volume Reconstruction with 3D Texture Hardware. Technical Report. 1994.TR93-027
[26]Westermann, R, T. Ertl, Efficiently using Graphics Hardware in Volume Rendering Applications. Computer Graphics(SIGGRAPH 98 Proceedings),1998:291-294
[27]Meipner,M., S. Guthe, W. Strasser, Interactive Lighting Models and Pre-integration for Volume Rendering on PC Graphics Accelerators. Proc Graphics Interface'02.2002:209-218
[28]Kruger. J., R. Westermann. Acceleration Techniques for GPU-based Volume Rendering. Proceedings of the 14th IEEE Visualization 2003(VIS'03)2003
[29]Roettger, S., S. Guthe. Smart Hardware Accelerated Volume Rendering. Proceedings of EG/IEEE TCVG Symposium on Visualization VisSym'03.2003
[30]Stegmaier, S., etal. A Simple and Flexible Volume Rendering Framework for Graphics-Hardware-based Ray Casting. Proceedings of the International Workshop on Volume Graphics'05.2005:187-195
[31]Klein, T., etal. Exploiting Frame-to-Frame Coherence for Accelerating High-Quality Volume Ray Casting on Graphics Hardware. Proceedings of IEEE Visualization'05,2005:123-230
[32]陈为,彭群生,鲍虎军,视点相关的层次采样：一种新的硬件加速体光线投射算法,软件学报(JOURNAL OF SOFTWARE),2006.17(3):P.587-601
[33]Woop, S., J. Schmittler, RPU:A Programmable Ray Processing Unit for Real Time Ray Tracing. Proceedings of ACM SIGGRAPH 2005
[34]John Pawasauskas, Volume Visualization With Ray Casting, http://web.cs.wpi.edu/～matt/courses/cs563/talks/powwie/pl/ray-cast.htm,1997
[35]G. Kinttel. VERVE:Voxel Engine for Real-Time Visualization and Examination. Computer Graphics Forum, 19(3):37-48, September 1993.
[36]G. Knittel. A Scalable Architecture for Volume Rendering. Computer and graphics, 19(5):653-665,1995.
[37]R. Crisp. Direct Rambus Technology:The Next Main Memory Standard. IEEE Micro,17(6), November 1997.
[38]H. P. Meinzer, K. Meetz, D. Scheppelmann, U. Engelmann, and H. J. Baur. The Heidelberg Ray Tracing Model. IEEE Transactions on Visualization and Computer Graphics,2(3):242-254, September 1996.
[39]J. Hesser, R. Manner, G. Knittel, W. Straβer, H. Pfister, and A. Kaufman. Three Architectures for Volume Rendring. In Proceedings of Eurographics'95, volume 14, No.3, Maastricht, The Netherlands, September 1995. European Computer Graphics Association.
[40]M. C. Doggett. An Array Based Design for Real-Time Volume Rendering. In 10th Eurographics Workshop on Graphics Hard ware, pages 93-101, August 1995.
[41]M. C. Doggett and G. R. Hellestrand. A Hardware Architecture for Video Rate Smooth Shading of Volume Data. In Eurographics Hardware Workshop, pages 95-102, September 1994.
[42]M. C. Doggett. Vizar:A video Rate System for Volume Visualization. PhD thesis, University of New South Wales,1996.
[43]H. Pfister. Architectures for Real-Time Volume Rendering. PhD thesis, State University of New York at Stony Brook, Computer Science Department, Stony Brook, NY 11794-4400,1996, MERL Report No. TR-97-04.
[44]H. Pfister, A. Kaufman, and F. Wessels. Towards a Scalable Architecture for Real-Time Volume Rendering. In Proceedings of 10th Eurographics Workshop on Graphics Hardware, pages 123-130, Maastricht, The Netherlands, August 1995.
[45]R. Osborne, H. Pfister, H. lauer, N. McKenzie, S. Gibson, W. Hiatt, and T. Ohkami. EM-Cube:An Architecture for Low-Cost Real-Time Volume Rendering. In Proceedings of the Siggraph/Eurographics Workshop on Graphics Hardware, pages 131-138, Los Angeles, CA, August 1997.
[46]A. Kaufman and R. Bakalash. Memory and Processing Architecture for 3D Voxel-based Imagery. IEEE Computer Graphics and Applications,8(6):10-23, November 1988.
[47]J. van Scheltinga, J. Smit, and M. Bosma. Design of an On-Chip Reflectance Map. In Proceedings of the 10th Eurographics Workshop on Graphics Hardware, pages 51-55, Maastricht, The Netherlands, August 1995.
[48]M. Meiβner, U. Machiraju, and W. Straper. VIZARD II:A Comparison of Normal Estimation Schemes. In IEEE Visualization Proceedings of the Siggraph/Eurographics Workshop on Graphics Hardware, pages 61-67, Lisbon, Portugal, August 1998.
[49]G. Kinttel. VERVE:Voxel Engine for Real-Time Visualization and Examination. Computer Graphics Forum, 19(3):37-48, September 1993.
[50]G. Kinttel. A PCI-based Volume Rendering Accelerator. In Proceedings fo the 10th Eurographics Workshop on Graphics Hardware, pages 73-82, August 1995.
[51]Levoy M.1998. Display of Surfaces from Volume Data. IEEE Computer Graphics and Application,8(3), 29-37
[52]Turk G.1992. Real-timing Polygonal Surface. Computer Graphics, proceedings, Aug.,55-64
[53]Westover L.1990. Footprint evaluation for volume rendering. Computer Graphics,24(4),367-376
[54]Cameron G.G. Undrill P E.1992. Rendering Volumetric Medical Image Data on a SIMD Architecture Computer, Proceedings of the Third Euor graphics Workshop on Rendering, May,135-145
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