Improved Gradient Estimation Methods for Rendering of Volume Data

The paper presents two methods that improve gradient estimation in 3D voxel space. The gradient estimation is an important step in the rendering and shading process to obtain realistic and smooth final images of visualized objects. The most used gradient estimation methods, gray-level gradient methods, Z-buffer gradient methods and binary gradient methods in some cases produce artifacts that appear as dark areas and staircase structures in a final image. To deal with the problem, two new methods for gradient estimation are suggested, the reverse gradient method and the angle difference method. The new methods were tested and compared with other gradient estimation methods. Measurements, which have been made on both the data and image levels, have shown that both developed methods improve the quality of volume data rendering.