The Texmap plugin is designed to render materials with a complex index of refraction (IOR). While standard materials (e.g., V-Ray, Corona Renderer) can calculate the Fresnel effect for dielectric materials like plastic using the IOR (n), metals require a more intricate Fresnel reflective curve. This curve is also influenced by an additional parameter called the extinction coefficient (k), defined as: η=n+ik Here, n and k determine two key characteristics of the Fresnel curve for a material: the reflectivity at normal incidence and the rate at which it fades to white at grazing angles.

The Texmap plugin can be used as a reflection color map in a material with the Fresnel option turned off, as the plugin performs its own Fresnel calculations.

Parameters

  • n: The IOR values for the Red/Green/Blue wavelengths (0.650, 0.510, and 0.475 µm).
  • k: The extinction coefficient values for the Red/Green/Blue wavelengths.

Presets

The plugin includes several presets for a quick start. To input custom n and k values, select the “Custom” preset.

Color Adjustments

For different colors (e.g., for various alloys), use the Color Adjustment parameters to modify Gamma, Hue, and Saturation values. This ensures the Fresnel curve remains correct while allowing color changes.

  • Gamma: Specifies the gamma correction value.
  • Hue Shift: Adjusts colors using a standard Hue spectrum. Range: -180 to 180.
  • Saturation: Controls the intensity or purity of colors. Lowering the value desaturates the color, while raising it intensifies the color. Range: -100 to 100.

Obtaining Values

You can find measured n and k values for many metals (e.g., Copper, Gold, Iron) on Refractive Index Database.

Installation

  1. Copy the file “ComplexFresnel_xxxx.dlt” to the MAXROOT\plugins directory (delete any older version of the file if present).
  2. Use the appropriate file for your 3ds Max version:
    • ComplexFresnel_2013.dlt: Compatible with 3ds Max 2013/2014
    • ComplexFresnel_2015.dlt: Compatible with 3ds Max 2015/2016
    • ComplexFresnel_2017.dlt: Compatible with 3ds Max 2017
    • ComplexFresnel_2018.dlt: Compatible with 3ds Max 2018