Icicles and sunbursts are two commonly-used visual representations of trees. While icicle trees can map data values faithfully to rectangles of different sizes, often some rectangles are too narrow to be noticed easily. When an icicle tree is transformed into a sunburst tree, the width of each rectangle becomes the length of an annular sector that is usually longer than the original width. While sunburst trees alleviate the problem of narrow rectangles in icicle trees, it no longer maintains the consistency of size encoding. At different tree depths, nodes of the same data values are displayed in annular sections of different sizes in a sunburst tree, though they are represented by rectangles of the same size in an icicle tree. Furthermore, two nodes from different subtrees could sometimes appear as a single node in both icicle trees and sunburst trees. In this paper, we propose a new visual representation, referred to as \emph{radial icicle tree} (RIT), which transforms the rectangular bounding box of an icicle tree into a circle, circular sector, or annular sector while introducing gaps between nodes and maintaining area constancy for nodes of the same size. We applied the new visual design to several datasets. Both the analytical design process and user-centered evaluation have confirmed that this new design has improved the design of icicles and sunburst trees without introducing any relative demerit.

翻译：冰柱图与旭日图是两种常用的树形结构可视化表示方法。冰柱图虽能忠实将数据值映射为不同大小的矩形，但常出现部分矩形过窄而难以辨识的问题。当冰柱图转换为旭日图时，每个矩形的宽度转换为环形扇区的弧长，通常大于原始宽度。旭日图虽缓解了冰柱图中窄矩形的问题，却不再保持编码一致性——在同一冰柱图中相同数据值的节点以等面积矩形呈现，但在旭日图中，不同树深度的同类节点却显示为不同大小的环形扇区。此外，不同子树中的两个节点有时会在冰柱图和旭日图中合并显示为单一节点。本文提出一种名为“径向冰柱图”（RIT）的新型可视化表示方法，该方法将冰柱图的矩形边界框转换为圆形、圆扇区或环扇区，同时在节点间引入间隙，并确保同等大小节点的面积保持恒定。我们将这一新型可视化设计应用于多个数据集，分析设计流程与以用户为中心的评估均证实：该设计在未引入任何相对缺陷的前提下，有效改进了冰柱图与旭日图的设计。