This Texmap plugin can be used to render materials with complex index of refraction (IOR): the regular material (for example V-Ray, Corona Renderer) can compute the Fresnel effect for dielectric materials like plastic based on the IOR of the material (n) – however metals have a more complicated Fresnel reflective curve that depends also on another parameter called extinction (k) coefficient:
η = n + ik.
n and k determine the two characteristics of the Fresnel curve for a material: the reflectivity at normal incidence and how quickly 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 of the material turned off (this plugin does its own Fresnel calculations).
n – the n (IOR) values for the Red/Green/Blue wavelengths (0.650, 0.510 and 0.475 µm).
k – the k (Extinction coefficient) values for the Red/Green/Blue wavelengths.
Presets – some presets for quick start (to enter other parameters (n, k) values it is necessary to select preset Custom).
If you need a bit different color (f. e. for various alloys), use a Color Adjustment parameters and adjust the Gamma, Hue, Saturation values. This way you still have the correct Fresnel curve and are just making color changes.
Gamma – specifies the gamma correction value.
Hue Shift – lets you change colors using a standard Hue spectrum. Range = -180…180.
Saturation – the intensity or purity of the colors. Lowering the Saturation value removes color, causing the color to tend toward grayscale, while raising it intensifies the color. Range = -100…100.
How to get values
The site http://refractiveindex.info/ has the measured n and k values for many metals like Copper, Gold, Iron etc.
Copy file “ComplexFresnel_xxxx.dlt” to MAXROOT\plugins (If you have installed older version – delete the old file!).
– File ComplexFresnel_2013.dlt compatible: 3ds Max 2013/2014
– File ComplexFresnel_2015.dlt compatible: 3ds Max 2015/2016
– File ComplexFresnel_2017.dlt compatible: 3ds Max 2017
Free for personal and commercial use.
01.10.2016 – v1.0.6
* Performance optimization (up to 50%).
25.04.2016 – v1.0.5
* Added support for 3ds Max 2017.
02.09.2015 – v1.0.4
* Fixed references issues.
25.05.2015 – v1.0.3
* Added standard Output dialog.
18.05.2015 – v1.0.2
* Minor bug fixes.
12.05.2015 – v1.0.1
* Fixed Thread Safety issues.
01.05.2015 – v1.0.0
* Stable version.
26.04.2015 – v0.9.0b
* Beta version.