IEEE Trans Vis Comput Graph. 2018 Jul;24(7):2103-2117. doi: 10.1109/TVCG.2017.2705182. Epub 2017 May 17.
Shading is a tedious process for artists involved in 2D cartoon and manga production given the volume of contents that the artists have to prepare regularly over tight schedule. While we can automate shading production with the presence of geometry, it is impractical for artists to model the geometry for every single drawing. In this work, we aim to automate shading generation by analyzing the local shapes, connections, and spatial arrangement of wrinkle strokes in a clean line drawing. By this, artists can focus more on the design rather than the tedious manual editing work, and experiment with different shading effects under different conditions. To achieve this, we have made three key technical contributions. First, we model five perceptual cues by exploring relevant psychological principles to estimate the local depth profile around strokes. Second, we formulate stroke interpretation as a global optimization model that simultaneously balances different interpretations suggested by the perceptual cues and minimizes the interpretation discrepancy. Lastly, we develop a wrinkle-aware inflation method to generate a height field for the surface to support the shading region computation. In particular, we enable the generation of two commonly-used shading styles: 3D-like soft shading and manga-style flat shading.
对于从事 2D 卡通和漫画制作的艺术家来说，阴影处理是一项繁琐的工作，因为他们需要定期在紧张的时间表内准备大量的内容。虽然我们可以通过存在的几何形状来自动生成阴影，但对于艺术家来说，为每个单独的绘图建模几何形状是不切实际的。在这项工作中，我们旨在通过分析干净线条画中皱纹笔触的局部形状、连接和空间排列来自动生成阴影。通过这种方式，艺术家可以将更多的精力集中在设计上，而不是繁琐的手动编辑工作上，并在不同的条件下尝试不同的阴影效果。为此，我们做出了三个关键的技术贡献。首先，我们通过探索相关的心理学原理来建模五个感知线索，以估计笔触周围的局部深度轮廓。其次，我们将笔触解释表述为一个全局优化模型，该模型同时平衡了感知线索所建议的不同解释，并最小化了解释差异。最后，我们开发了一种褶皱感知膨胀方法来生成一个高度场，以支持阴影区域的计算。特别地，我们能够生成两种常用的阴影风格：类似 3D 的柔和阴影和漫画风格的平面阴影。
