SSR
Screen-space reflections
Also known as: Screen-Space Reflections
Definition
SSR (Screen-Space Reflections) computes glossy reflections by ray-marching the depth buffer in screen space. It is fast and handles dynamic geometry without preprocessing, but it can only reflect what is already on screen — anything outside the camera or behind another object falls back to reflection probes or cubemaps. SSR is the standard for wet floors, puddles, and polished surfaces in modern titles.
In production
SSR computes glossy or mirror-like reflections by ray-marching through the depth buffer in screen space, stepping along the reflection vector until it intersects existing depth data, then sampling that pixel's colour as the reflection. It is fast relative to ray tracing and handles dynamic geometry without any preprocessing or probe baking, which is why it's the standard technique for wet floors, puddles, and polished surfaces in modern titles. Its core limitation is that it can only reflect what's already visible on screen: anything behind the camera, occluded by another object, or just outside the frame produces a reflection gap, which engines typically fill by falling back to reflection captures or a screen-space global illumination system like UE5's Lumen. A recognizable SSR artifact is reflections "sliding off" the edge of screen as the camera pans, since the source pixel data simply isn't there anymore.
