模擬雙向貼圖函數材質上漆之效果

Abstract

雙向貼圖函數是一個非常擬真的材質表示法，然而對使用者而言，它並沒有對資料提供良好的控制與編輯能力。使用者沒有辦法用簡單而有效的方式改變雙向貼圖函數資料。我們提出一個方法來模擬以雙向貼圖函數表示之材質上漆後的外觀。我們首先將基於圖像的雙向貼圖函數轉換為一個簡單的表示法，這個表示法是由高度圖和隨空間變化的雙向反射分佈函數所組成。這個表示法允許我們模擬漆在物體表面的流動，同時估計上漆之後的材質反射性。在渲染的過程中，我們結合一個現存的雙向貼圖函數渲染技術，以及修改過後的材質資料，來模擬以雙向貼圖函數表示之材質上漆後的結果。我們嘗試提供改變材質外觀的能力，同時保留原始雙向貼圖函數材質的感受與印象。

The Bidirectional Texture Function (BTF) is a very realistic material representation, but it does not offer the user good control and editability over the data. Users can not change the BTF data in a simple and effective way. We present a method for simulating the painted appearance of a material that is represented by the Bidirectional Texture Function. We first transform the image-based BTF into a simple representation that is composed of a height-field and a spatially varying bidirectional reflectance distribution function (SVBRDF). This representation allows us to simulate the appearance of paint on the surface and to estimate the reflectance of the material after being painted. During rendering, we combine a currently existing BTF rendering technique and the modified material data to simulate the painted appearance of the BTF material. Our experiments show that the proposed approach can change the material appearance while preserving the impressions and feelings of the original BTF.