互動式全域照明 – 可變動的光源位置

Abstract

對於互動式全域照明(Interactive Global Illumination)計算，本篇論文提出結合光子圖(Photon Map)及多項式貼圖(Polynomial Texture Map)方法用來加速繪製場景(Scene)當其光源位置變動時的照度計算。為了結合上述兩種方法，我們提出以光子密度為單位的光子密度圖(Photon Density Map)及儲存方程式係數的多項式照度圖(Polynomial Illumination Map)來達成此目的。 在場景照明計算上，我們採用光子映射法(Photon Mapping)，由光源向場景發散光子及進行追蹤，並將光子記錄於光子圖中。其後，將場景進行空間等量分割，計算空間中取樣點的光子密度並儲存於光子密度圖中。我們取樣光源移動的位置空間，完成所有光子密度圖的收集，將光子密度變化和光源位置的關係，以三次方多項式逼近其結果，並將係數記錄於多項式照度圖中。在彩現(Rendering)場景上，我們採用反向光跡追蹤(Backward Ray Tracing)方式，將與場景中物體產生交點的光子密度經由多項式照度圖還原。如此在光源變動至新位置時，便不用重新發散光子，達到加速場景照度計算之目的。

Although global illumination can offer realistic effect for scene rendering, most of the techniques require vast amount of computations as well as tremendous amount of time for rendering. Thus it is still not applicable for interactive or real time applications. In this thesis, we propose a method which can compute global illumination for complex scenes very efficiently even when the position of light source is dynamically changing. The method uses a polynomial illumination map to approximate the shading of the scene for all possible positions of light source. The construction of the polynomial illumination map is based on the photon density map which is derived from traditional photon map.