此篇論文為研究GPU如何在繪製物件程序中更為簡化(從程式設計師觀點)及改善(從run-time觀點)。我們對於自動偵測遮擋來避免繪製被遮擋的物件，提出了修改軟體和硬體的方法。我們也考慮了子物件。此方法在部分遮擋有不少好處，而且同一物件的子物件也有機會互相遮擋。並且它們的繪製順序能夠以低本動態排序，因此增加同一物件互相遮擋的機會。除此之外本篇論文也研究自動產生hull及子物件的產生。

This thesis looks at how the GPU’s processing of objects can be simplified (from the programmer’s point of view) and improved (from the run-time point of view). We propose both software and hardware modifications for automatic occlusion detection to avoid rendering occluded objects. We also consider subobjects. The method takes advantage of partial occlusion opportunities and also allow for parts of an object to self-occlude other parts of the same object. Their rendering sequence can be dynamically reordered at minimal cost, thereby increasing the self-occlusion opportunities within the object. In addition, this thesis investigates methods of automatic hull creation and subobject creation.

1. Introduction …………...........................................................................1
2. Related Work .........................................................................................7
2.1 Hardware for culling non-visible areas ............................................7
2.1.1 GPU hardware for clipping ......................................................7
2.1.2 GPU hardware for z-culling ...................................................10
2.1.3 GPU hardware for Back-face culling ....................................13
2.2 Existing software approaches for occlusion culling .......................14
2.2.1 Statically reordering triangles within an object .....................15
2.2.2 Performing an occlusion query before rendering an object ...17
2.2.3 Using bounding boxes for conservative queries ....................19
2.2.4 Various kinds of hulls that may be used to bound an object .21
3.An Overview of the Rendering Process for OpenGL ES 2.0 on a GPU 25
3.1 The interactions of the software and hardware .……..…...………25
3.1.1Rendering a 3D object: From the game code’s point-of-view25
3.1.2 OpenGL ES 2.0 API function using in game ………………26
3.1.3 Trigger hardware to render ……………………………….28
4. Methodology ………………………………..…………………………30
4.1 Details of how our method can obtain new benefits from occlusion .......................................................................................30
4.1.1 A wrapper around the existing function …………….………30
4.1.2 The method we designed for hardware ……………………31
4.2 A method of subregion extraction to obtain smaller bounding boxes …………………………...……………………...................34
4.2.1 Optimize the regions ...............................................................34
4.2.2 The hull implementation and optimization ………………….37
4.3 Details of how our method has been modified to support subregions and non-rectangular hulls …………………………...39
4.3.1 A wrapper around the existing function …………………….39
4.3.2 Intermediate Processing ……………………………………..41
4.3.3 New method to support subregions with fragment shader ….43
5. Experimental Setup …………………..……………………………….45
5.1 The cost/benefit model ……………………………………….....45
5.2 Benchmarks ……………………………………………………52
6. Results……………..………………………………………………..…55
7. Conclusion …………………………………………………………….65
References ……………………………………………………………….66

[1] Pedro V. Sander, Diego Nehab and Joshua Barczak. “Fast Triangle Reordering For Vertex Locality and Redraw.” ACM Transactions on Graphics. 2007.
[2] T Sus, C Koch, C Jahn, and M Fischer. “Approximative occlusion culling using the hull tree” Proceedings of Graphics Interface 2011.
[3] Hansong Zhang. “Effective Occlusion Culling for the Interactive Display of Arbitrary Models”, Ph. D. dissertation, Department of Computer Science, UNC-Chapel Hill, July 1998.
[4] Dean Sekulic. ”Chapter 29. Efficient Occlusion Culling” http://http.developer.nvidia.com/GPUGems/gpugems_ch29.html, Copyright c 2004 by NVIDIA Corporation.
[5] John Ratcliff. “HACD : Hierarchical Approximate Convex Decomposition“, http://codesuppository.blogspot.tw/2011/05/hacd-hierarchical-approximate-convex.html, May 2011
[6] “San Angeles Observation” (2004, 2005)
http://jet.ro/visuals/4k-intros/san-angeles-observation/
[7] The Free 3D Models http://thefree3dmodels.com/