Screen Space Reflection

What is Screen Space Reflection?

Screen Space Reflection is a rendering technique that approximates reflections by tracing reflection rays through the rendered image, depth buffer, and surface data already available on screen. The technique is commonly abbreviated as SSR and is used in real-time graphics to add reflections without the full cost of hardware ray tracing or offline path tracing.

How it works

Screen Space Reflection works after the main scene has been rendered by projecting a reflected view direction into screen space and ray marching across the depth buffer to find a likely reflected surface. When a hit is found, the renderer samples the scene color buffer and blends that result onto glossy or wet materials based on roughness, Fresnel response, and other shading inputs. SSR is fast because it reuses data that is already rendered, but it can only reflect objects that are currently visible on the screen. Common limitations include missing off-screen reflections, edge fading, depth-thickness errors, temporal shimmer, and artifacts on very rough or thin geometry.

Screen-space reflections vs ray-traced reflections

Treat SSR as the cheap first layer: it grounds glossy and wet surfaces but loses anything off screen, so always configure reflection probes or ray tracing as its fallback. Reserve ray-traced reflections for mirrors and shots where accuracy justifies the GPU cost.

Use cases

• Tuning reflective materials on floors, metals, glass, or wet surfaces in a game engine.

• Diagnosing reflection artifacts that appear only from certain camera angles.

• Balancing visual quality and frame rate when choosing between SSR, reflection probes, planar reflections, and ray tracing.