In addition to the below content, see also: Corona Color Map at Chaos Docs
Corona Color is a simple map which outputs the user-defined color. The color values can be defined using:
- 3ds Max Color Selector or Corona Color Picker (Solid color)
- HDR RGB values (Solid HDR color)
- Kelvin temperature (Kelvin temp.)
- Hexadecimal code (Hex color)
The output value can also be multiplied and its alpha can be specified. Input can be set to either gamma-corrected or linear color space.
The "Input values are in linear color space" checkbox defines how the color values are interpreted. It should be usually left enabled to make sure the specified color and the output color are visually identical.
Examples
1. A typical use of the Corona Color map is specifying a procedural map's colors to the exact, desired values:
Material setup:
2. Another possibility is using it to define specific color values where it is otherwise impossible. An example of this is specifying custom Fresnel IOR values.
Note: usually this is not needed as the Fresnel IOR value can be specified directly in the material's properties (Reflection > Fresnel IOR). This example only demonstrates an advanced use of the Corona Color map, and generally this is not a typical workflow.
A simple black material with Fresnel IOR set to 1.52 in its properties (this is the default value):
Material setup:
If we connect the Corona Color map to the Fresnel IOR map slot of our material, it will generate some unexpected results. This is because the Fresnel IOR does not accept standard color input:
Fresnel IOR using a Color Color map with pure white color set:
Material setup:
Setting Fresnel IOR to a darker, gray color does not seem to clarify the situation either:
Material setup:
To overcome this, and correctly set a custom Fresnel IOR value we can set the Corona Color map to pure white, and then use its Output multiplier parameter:
Custom Fresnel IOR value set to 1.52. Note that the result is identical to a Corona Material using Fresnel IOR set to 1.52 visible in the first image example:
Material setup:
This method can be used to create a single material where the Fresnel IOR value varies across its surface:
A Noise map is used to define where the Fresnel IOR value is lower (darker material) and where it is higher (brighter, metallic material):
Material setup:
(Corona Color 1 - Output multiplier 1.52; Corona Color 2 - Output multiplier: 32)
Falloff map is used to define where the material is darker (camera-facing angles) and where it is brighter and more metallic (grazing angles):
Material setup:
(Corona Color 1 - Output multiplier 1.52 or lower; Corona Color 2 - Output multiplier: 32)