Implicit surfaces are known for their ability to represent smooth objects of arbitrary topology thanks to hierarchical combinations of primitives using a structure called a blobtree. We present a new tile-based rendering pipeline well suited for modeling scenarios, i.e., no preprocessing is required when primitive parameters are updated. When using approximate signed distance fields, we rely on compact, smooth CSG operators - extended from standard bounded operators - to compute a tight volume of interest for all primitives of the blobtree. The pipeline relies on a low-resolution A-buffer storing the primitives of interest of a given screen tile. The A-buffer is then used during ray processing to synchronize threads within a subfrustum. This allows coherent field evaluation within workgroups. We use a sparse bottom-up tree traversal to prune the blobtree on-the-fly which allows us to decorrelate field evaluation complexity from the full blobtree size. The ray processing itself is done using the sphere-tracing algorithm. The pipeline scales well to surfaces consisting of thousands of primitives.

翻译：隐式曲面因其通过称为blobtree的结构对基本体进行分层组合以表示任意拓扑光滑对象的能力而闻名。我们提出了一种新的基于瓦片的渲染管线，非常适合建模场景，即在更新基本体参数时无需预处理。当使用近似有符号距离场时，我们依赖于紧凑且光滑的CSG运算符（从标准有界运算符扩展而来）来计算blobtree中所有基本体的紧密感兴趣体积。该管线依赖于一个低分辨率A缓冲区，用于存储给定屏幕瓦片中的感兴趣基本体。随后在光线处理过程中使用该A缓冲区，以在子视锥体内同步线程。这使得工作组内能够进行一致的场评估。我们采用稀疏的自底向上树遍历来动态修剪blobtree，从而将场评估复杂度与完整blobtree大小解耦。光线处理本身使用球追踪算法完成。该管线能够很好地扩展到由数千个基本体组成的曲面。