全域照明中結合模糊陰影與影像平面光子映射技術之研究

Abstract

即時的全域照明技術在電腦圖學領域中，一直是一門重要的課題。過去受限於硬體的計算能力,運用於遊戲或動畫中的渲染技術往往必須在速度與畫質之間作取捨；但隨著繪圖處理單元(GPU)的進步，使用繪圖硬體為基礎的渲染演算法將成為即時渲染的關鍵。 本篇論文提供了一個新的以繪圖硬體為基礎的即時全局照明演算法，他是結合了影像平面光子映射(Image space photon mapping)以及其他模糊陰影的技術。藉由化簡光子散射的步驟以及使用影像平面的模糊陰影演算法，我們改進了原有影像平面光子映射的繪圖品質，並保有即時繪圖的演算速度。另外我們也使用泛用型光線追蹤引擎(Nvidia Optix)來讓所有的演算步驟都在繪圖硬體上執行。我們經由實作證明本演算法能夠支援多種光學現象的結果，像是間接照明以及折射光的聚焦，並且能以即時的速度描繪。

Real-Time global illumination in computer graphic is a very important topic. With the enhancement of GPU architectures in recent years, GPU-based rendering algorithms have become the key to perform high quality images in real time. In this thesis, we propose a GPU-based real-time global illumination algorithm by combining image space photon mapping and other soft shadow effects. We simplify the photon splatting phase by using photon quads instead of photon volumes, and use image space soft shadow algorithm to improve image quality while preserving real-time rendering speed. Moreover, photon tracing is implemented by using Nvidia Optix ray tracing engine. Our system runs totally on the GPU, and can handle most optical phenomena, such as indirect lighting and caustics. We demonstrate that the results can be displayed at real-time frame rates.