藉由觀察物體環繞的影像估測物體的表面反射特性

Abstract

最近幾年，虛擬實境的應用愈來愈廣泛，人們對於虛擬世界中的物體及場景，總希望它能夠與真實世界一模一樣，假如能夠取得真實物體的幾何模型與表面反射特性，就能夠在電腦圖學中真實地描繪出物體的反射現象，進而得以在虛擬世界中產生與真實物體相似的虛擬影像。本篇論文的目的，是要以觀察物體表面反射特性的方式，估測出物體表面的反射特性。 我們的作法，是採用單一光源來進行照明，並利用攝影機來觀察被放置在轉盤上的物體，而取得每隔一個固定的角度所拍下的影像。接著是分析物體觀察的結果，基於所使用的Phong's model，我們可以取得物體反射的ambient項、diffuse項、以及specular項。最後，取得了物體的幾何模型與表面的反射特性之後，我們就可以在不同的照明狀況下，繪製出最真實的影像，包括光源位置與顏色的改變。

In recent years the applications of virtual reality become popular. People always want the virtual objects and scenes look natural like the real ones. If we can get the geometric model and surface reflectance properties of the real object under consideration, then we can render the virtual object just like the real one. The primary objective of this thesis is to estimate reflectance coefficients of an object from a sufficient number of images taken around it. In our method we use a single light source to illuminate the object, and we use a fixed camera to take the pictures of the object which is rotating by a fixed degree on a turn table. Then, we estimate reflectance coefficients of the object based on the Phong's model, including the ambient term, diffuse term, and specular term. After we obtain the object geometric model and surface reflectance properties, we can render the object image with a varying light source which changes its location and its intensity.