Fresnel
Edge-on reflection increase
Also known as: Fresnel effect
Definition
Fresnel describes how a surface's reflectivity increases as the viewing angle approaches grazing — looking at water from above shows mostly the bottom, but at a glancing angle it becomes a near-mirror. PBR shaders compute Fresnel automatically per pixel using the surface normal and view direction. Artists use Fresnel masks in shader graphs to drive rim lighting, hologram effects, soft falloffs on transparent materials, and stylised wind on foliage.
In production
In UE5 Material Editor: drop a Fresnel node, plug into Emissive for rim glow, into Opacity for soft edges, or into a Lerp for view-dependent colour shifts. The most common stylised-game trick: Fresnel × character colour fed into Emissive = instant rim-light shader, widely used in games like Overwatch and Valorant to make characters read clearly against busy backgrounds. The Fresnel node exposes an Exponent input that controls falloff sharpness — a low exponent (1-2) produces a broad, soft glow while a high exponent (8+) restricts the effect to a thin edge, useful for tightening a hologram or shield effect. A frequent mistake is applying Fresnel-driven opacity to double-sided transparent geometry without also handling render order, since Fresnel edges on both the front and back faces of a sphere can cause visible sorting artifacts.
