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：基于水平线的间接光照方法通过沿给定方向对样本间的水平角差进行解析积分，能高效估算屏幕空间中的漫反射光弹射。与其他基于水平线的方法类似，该技术无法正确模拟光线穿透薄表面后的传播。我们提出可见性位掩码概念，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）的位域替代两个水平角。该方法在保持基于水平线方法高效性的同时，允许光线穿透恒定厚度的薄表面，且通过采样多个可见性锥体实现比弯折法线更精确的环境光照。与现有屏幕空间方法相比，该技术能在最小化噪声并保持低性能开销的前提下，提升环境光遮蔽、间接漫反射和环境光照的视觉质量。