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This page provides information on the V-Ray TexFresnel node.

Overview

V-Ray Fresnel is a simple texture map that blends two colors or maps based on the viewing angle and an index of refraction. For example, you can connect the Fresnel texture to the reflection color of a V-Ray material in order to create fresnel reflection.

V-Ray for Houdini > V-Ray Fresnel > VRayFresnel_Hero.png

Parameters

Front Color – The color for the texture when viewed frontally (refraction color).

Side Color – The color for the texture when viewed at a grazing angle (reflection color).

Fresnel IOR – Index of refraction to use when calculating the Fresnel term.

Refract IOR – Specifies the refraction IOR for the underlying surface. This is ignored if the surface has a volume shader (the volume IOR is used instead).

Contribute to Fresnel IOR Render Element – When enabled, the V-Ray Fresnel Texture contributes to the Fresnel IOR Render Element.

V-Ray for Houdini > V-Ray Fresnel > Hou19_VRay6_Fresnel_Parameters.png

Example: V-Ray Fresnel vs. Fresnel Reflections

One use for V-Ray Fresnel is to give a V-Ray Material a stronger Fresnel effect on reflections than the Use Fresnel option. Below is a simplified example to show how V-Ray Fresnel changes the degree of reflectivity on a spherical object.

A V-Ray Material is applied to both objects below, with different material setups. Where V-Ray Fresnel is used, the front of the object (the part that faces the camera) is much less reflective than the sides of the object. The degree of reflectivity set by V-Ray Fresnel affects both the reflected background and the reflection of the rectangular light source.

V-Ray for Houdini > V-Ray Fresnel > VRayFresnel_off.jpg
V-Ray Material with white Reflect color, Use Fresnel enabled

V-Ray for Houdini > V-Ray Fresnel > VRayFresnel_on.jpg
V-Ray Material with V-Ray Fresnel map in Reflect channel, Use Fresnel disabled
Front reflectivity = 0.01
Side reflectivity = 1.0