對於全動態場景之似真實互動式全域照明渲染

Plausible Interactive Global Illumination Rendering for Fully Dynamic Scenes

陳彥瑜(Yen-Yu Chen)

指導教授 ： 簡韶逸

國立臺灣大學/電機資訊學院/電子工程學研究所/博士(2016年)

https://doi.org/10.6342/NTU201601254

摘要

全域照明在真實影像合成中扮演了很重要的角色。隨著繪圖硬體的快速發展，大多數的研究著重於在繪圖處理器上開發互動式的或即時的全域照明演算法。由於光線追蹤可使渲染影像達到很高的真實度，以及對於電腦處理能力具有相當好的擴展性，因此成為了一個很普及的全域照明解法。然而，對於即時應用來說，渲染物理正確之全域照明是相當不容易的。雖然透過一些空間資料結構可以加速光線追蹤至互動式的渲染速度，它依然無法有效率地處理全動態場景的渲染。這篇論文根據這個問題提出了可以對全動態場景進行互動式地似真實全域照明渲染。
為了達到這個目的，我們開發了一些適用在繪圖硬體上且可以產生似真實全域照明的渲染技術。它們均可以互動式的渲染速度處理全動態場景，並且產生與光線追蹤非常相似的渲染影像。首先，我們著重於單一反彈間接照明之渲染，它可以透過增加適量的計算成本 大幅地增加渲染影像的真實感。我們提出一以點為基礎的渲染技術，它透過查詢小型延期陰影貼圖來取代光線追蹤所要處理的交點詢問。進一步為了獲得較物理正確的渲染影像，我們調查了交點準確性與渲染品質之間的關係，並且提出透過高解析度立體像素來量化交點，而這些立體像素可以被有效率且緊密地編碼在繪圖處理器中的二維貼圖中。此外，我們提出照明驅動立體像素來解決單一反彈間接照明所需要的大量記憶體用量問題。我們將照明驅動立體像素套用到立體像素光線追蹤和立體像素椎體追蹤演算法，並展示它在記憶體使用量上的高效率。最後，我們透過提出的特性抽取技術來實現全動態場景的基於立體像素路徑追蹤演算法，它可產生多反彈間接照明並模擬完整的光線傳遞。此技術可以在運行時即時地獲得二次光線的交點特性。這個特性使得我們可以在高階析度立體像速進行互動式渲染，這也是產生高品質全域照明效果的關鍵。

關鍵字

全域照明 ； 立體像素

並列摘要

Global illumination (GI) rendering plays an important role in realistic image synthesis. With the rapid development of graphics hardware, much effort has been put into developing interactive or real-time GI algorithms. Ray tracing has become a ubiquitous solution on account of its high achievable realism and its superior scalability in computer power. However, the rendering of physically-correct GI is highly demanding for real-time applications. Although interactive performance is possibly achieved by adopting certain spatial acceleration structure (AS) for ray tracing or relying on certain precomputation, they cannot efficiently deal with fully dynamic scenes. This dissertation addresses the problem by introducing plausible interactive global illumination rendering for fully dynamic scenes.
To that end, we develop several rendering techniques for producing plausible GI effects using graphics hardware. All of them can render fully dynamic scenes at interactive speeds and produce images very similar to those of ray tracing. First, we focus on the rendering of single-bounce indirect illumination, which adds significant visual realism to the rendered image with moderate computational cost. We present a point-based technique to replace the process of the intersection query of ray tracing with simple lookups on small deferred shadow maps. Further, in order to generate high-quality GI effects, we investigate the relation between the intersection accuracy and rendering quality and quantize intersections using high-resolution voxels, which can be efficiently created by GPUs and compactly encoded in a few 2D textures. Moreover, we address the issue of memory consumption with single-bounce indirect lighting and propose the use of lighting-driven voxels (LDVs). The LDVs have been successfully applied to both voxel ray tracing and voxel cone tracing algorithms to demonstrate their efficiency in memory usage. Finally, to simulate complete light transport with multiple-bounce indirect lighting effects, such as multiple reflections and refractions, we propose voxel-based path tracing that enables interactive rendering of fully dynamic scenes via the proposed attribute extraction technique, which can efficiently retrieve intersection attributes of secondary rays on-the-fly at runtime without storing them in advance. This enables rendering using high-resolution voxels that is the key to produce high-fidelity global illumination effects.

並列關鍵字

Global illumination ； Voxel

參考文獻

[1] H. W. Jensen, Physically Based Rendering, Second Edition: From Theory To Implementation. Morgan Kaufmann Publishers Inc., 2010.

[2] H. W. Jensen, Realistic image synthesis using photon mapping. A. K. Peters, Ltd., 2001.

[3] C. Dachsbacher and M. Stamminger, “Reflective shadow maps,” in Proc. of I3D, 2005, pp. 203–231.

[4] M. Sugihara, R. Rauwendaal, and M. Salvi, “Layered reflective shadow maps for voxel-based indirect illumination,” in Proc. of High Performance Graphics, 2014, pp. 117–125.

[5] K. Myszkowski, T. Tawara, H. Akamine, and H.-P. Seidel, “Perception-guided global illumination solution for animation rendering,” in Proc. of ACM SIGGRAPH, 2001, pp. 221–230.