Horizon-based indirect illumination efficiently estimates a diffuse light bounce in screen space by analytically integrating the horizon angle difference between samples along a given direction. Like other horizon-based methods, this technique cannot properly simulate light passing behind thin surfaces. We propose the concept of a visibility bitmask that replaces the two horizon angles by a bit field representing the binary state (occluded / un-occluded) of N sectors uniformly distributed around the hemisphere slice. It allows light to pass behind surfaces of constant thickness while keeping the efficiency of horizon-based methods. It can also do more accurate ambient lighting than bent normal by sampling more than one visibility cone. This technique improves the visual quality of ambient occlusion, indirect diffuse, and ambient light compared to previous screen space methods while minimizing noise and keeping a low performance overhead.

翻译：基于地平线的间接光照通过沿给定方向分析样本间地平线角度差的解析积分，有效估计屏幕空间中的漫反射光反弹。与其它基于地平线的方法类似，该技术无法正确模拟光线穿过薄表面后方的情况。我们提出可见性位掩码的概念，用表示半球切片周围均匀分布的N个扇区二进制状态（遮挡/未遮挡）的位字段替代两个地平线角度。该方法在保持基于地平线方法效率的同时，允许光线穿过恒定厚度表面后方。通过采样多个可见锥体，它还能实现比弯曲法线更精确的环境光照。与以往的屏幕空间方法相比，该技术在最小化噪声和保持低性能开销的同时，显著提升了环境光遮蔽、间接漫反射和环境光照的视觉质量。