In addition to the below content, see also: Corona Physical Material at Chaos Docs
What is it?
Whenever you need to create a material in Corona, the Corona Physical Material should be your starting point. As the standard tool for shading, it is designed to handle everything from simple, basic surfaces to highly complex, realistic materials, all while taking the guesswork out of 3D rendering.
Under the hood, the Physical Material strictly follows the laws of physics and energy conservation. This means you do not have to worry about accidentally breaking your scene with unrealistic settings - no matter how you tweak the parameters, it is built to guarantee a natural, photorealistic result.
The Physical Material also includes presets that you can easily select from a dropdown menu. These include materials such as Aluminium, Brass, Chrome, Copper, Diamond, Glass, Gold, Iron, Mirror, Plastic, Plexiglass, Satin, and even Velvet.
Why was it added?
The Corona Physical Material was added as the replacement of the old Corona Material, now called Corona Legacy Material. Some of the benefits of the Physical Material include:
- The ability to get more realistic and physically plausible results easier.
- Better and easier layering system without the need to set up complex Layered Material networks (clearcoat, sheen).
- Compatibility with other software following the physically-based (PBR) guidelines .
When to use the Corona Physical Material?
The Physical Material should be used as the new default for any newly created materials.
Corona Physical Material Basics
Metalness: Metal & Non-Metal(Dielectric) and how are they controlled by base color.
When looking at the basic parameters, you will notice that the Corona Physical Material is set to Non-metal by default. This mode represents dielectric materials - which, from a physical standpoint, are simply materials that do not conduct electricity. Because of this, when light hits a dielectric, a portion of it reflects off the surface, while the rest enters the object where it is either scattered to give the object its base color, or transmitted right through. Working in this mode makes it easy to create a huge variety of physically accurate surfaces. Because non-metal materials can be either opaque or transparent, this is the perfect setting for building everything from wood and plastics to glass, crystals, and organic matter.
Wooden body and glass pearls are considered as dielectric, non-metal materials, while the instrument's strings and black metallic tuning keys are metals.
In the case of a metallic base layer, Metals are opaque and defined only by their reflection color, which is set by the base color parameter. However, the reflection color for metals (exclusively) at grazing angles can be edited through the use of Edge Color.
Examples: The following example showcases the differences metalness can make on any given material simply by changing metalness mode to metal or non-metal (dielectric).
Full-size comparison link: https://corona-renderer.com/comparer/WPF2WZ
When creating metals, you can easily match real-world references just by tweaking the Base Color and Edge Color. This approach gives you complete artistic control over the final look and works perfectly for the vast majority of your scenes. However, if you need strict physical accuracy, we recommend using Complex IOR - a feature we will explore further down in this article.
In the comparison below, you can see a physically accurate metal driven by Complex IOR on the left, contrasted with an artistic, custom green Edge Color on the right.
(Full-size comparison link: https://corona-renderer.com/comparer/phHbaC)
Note: You can also use a texture map to control the metalness of your material. When you plug in a texture, black areas (a value of 0) tell the material to be a non-metal, while white areas (a value of 1) tell it to be a metal.
Any shades of gray in between will create a mix of both. While a surface cannot technically be a metal and a non-metal at the exact same time in the real world, these gray values are perfectly valid and happen often in 3D. You will naturally see this blending when a non-metal coating covers a metal surface - like spray paint or dirt over steel - or where the borders between the two materials soften due to texture filtering and anti-aliasing.
Base Tail
You can increase the tail of the base layer's bidirectional scattering distribution (GGX-BSDF), or in simple terms, control stronger reflections outside of reflection (peaks) highlights. To translate that from “light transport speak”, it means reflections will take on a softer and more distributed look with higher Tail values. While similar to raising the Roughness, the result is very different, with the sharp reflection still visible, and a softer pearly look that gives more “depth” to the surface.
See: What is the Base Tail - C4D?
Mapped base tail effect on metallic surface, Full-size comparison link: https://corona-renderer.com/comparer/e2Svho
This parameter can be found in the Advanced Options of CoronaPhysical Mtl, default values of 0 correspond to the standard scattering distribution, while increasing this value will lead to a longer tail. For more in depth explanation with examples please visit this page.
Note: The term tail, can be defined as the soft falloff that gradually "tails-off" from a sharp-highlight center of a light source as it is being reflected on a surface.
IOR (Non-Metal only) for Reflection & Refraction
The IOR value is solely available for non-metal materials, it controls the amount at which a light ray is being bent when entering an object (medium) and how much of it is being reflected. A value of 1.0 will result in no refraction or reflection (the index of refraction of air is normally around 1.0003), while for example, a value of 1.5 IOR can be suitable for generic glass materials.
Champagne glass, generic IOR 1.52
Contrary to the old CoronaMtl, now labeled as CoronaLegacy Mtl, Corona Physical's IOR is bound to a physically plausible range of 1.0 and up to 3.0, and its reflection/refraction IOR values are interlinked in a physically plausible manner. In the real world, there are no non-metal (dielectric) materials with an index of refraction (IOR) higher than 3.0.
Examples:
This first example shows exactly how the Index of Refraction (IOR) changes both how light bends through a material (refractive distortion) and how strongly the surface reflects. Just a quick note - to keep things looking natural, the impure glass on the far left had its absorption slightly darkened.
Moving from left to right, you will see generic impure glass with an IOR of 1.5, pure flint glass with an IOR of 1.62, and lead crystal glass with an IOR of 1.8.
Full-size comparison link, only for generic and flint glass: https://corona-renderer.com/comparer/bWLX7s
Note: With the new Corona Physical Material, you can now have anisotropic refraction to go along with anisotropic reflection, something that was previously impossible.
Specular to IOR mapping
IOR mode can now be set to Specular; in such a case, the value of IOR will be treated as a specular value, which is then internally converted to IOR using an established formula. This parameter can be found in the Advanced section within the Corona Physical Material. It can also be changed into a global parameter within the Corona Renderer Preferences, menu Corona > Preferences > Physical material defaults: default IOR mode.
In the following image comparison, the material on the left is utilizing a specular map. On the right side, you will see the same material with an unmapped IOR and a default value of 1.5.
Full-size comparison link: https://corona-renderer.com/comparer/H6WJaV
Roughness
The Roughness parameter controls how smooth the base layer's surface is. A value of 0 (black color if using a texture) gives a completely smooth surface which leads to sharp reflections, while a value of 1 (white color if using a texture) gives fully rough surface leading to blurred reflections.
Generally speaking, a smoother surface will reflect light much more strongly, while a rougher one will give you a soft, matte appearance.
Low roughness against higher value roughness: https://corona-renderer.com/comparer/zjUHXx
Examples: The following examples showcase how roughness values can affect refractive and opaque materials. As a first example, a metallic pole with a roughness value of 0.1 (left side) against a value of 0.5 (right side).
(Full-size comparison link: https://corona-renderer.com/comparer/dFxcad
Next up, a frosted lamp-bulb coated with glossy finish against a clear glass one, same IOR values different roughness. The frosted lamp has a roughness of 90%, while the clear glass one a 2%:
Full-size comparison link: https://corona-renderer.com/comparer/fjMoOJ
Roughness values affect both reflection and refraction equally. Rough refractive materials like etched glass (frosted, sandblasted, etc.) won't return any sharp reflections if their roughness value is high. In a proper manner, a coated rough surface can introduce both underlying rough surface but also glossy coating, through the use of Clearcoat as we can see below.
Full-size comparison link: https://corona-renderer.com/comparer/szNYfS
Note: Roughness mode can be modified to Glossiness in the "Advanced" section within the material (per material change); additionally, in the Corona Renderer Preferences, menu Corona > Preferences > Physical material defaults, it can be changed as a roughness/glossiness global default. The terms Glossiness and Roughness are interchangeable; they are simply the inverts of each other. In the case of inverting glossiness maps into roughness within Cinema 4D, do note to avoid using linear invert function like those from CoronaColor Correct. Instead, resort to inverting the native C4D bitmap's "Black Point"/"White Point" values (from zero to one and vice-versa), or you can use a Filter Shader and invert the "Low Clip" and "High Clip" values as well.
Below you will find an example rendered with glossiness (left) and roughness maps (inverted) (right); the rendered result remains unchanged between the two modes.
Full-size comparison link: https://corona-renderer.com/comparer/NH6AhF
Clearcoat
Think of a Clearcoat layer as a transparent finish or varnish applied over a surface. In the real world, you see this often on car paint - a base layer of color is applied first, and then a glossy clear coat is added on top.
In the Corona Physical Material, you will typically use a Clearcoat over a matte base surface. There are a few key reasons you might want to add this layer to your material:
Adding a Finish: To apply a protective coating or varnish over a base material, like a glossy finish on a wooden floor.
Adjusting Reflections: To change the overall index of refraction (IOR) or introduce a different type of glossiness on top of the base layer.
Adding Depth and Color: To tint the surface or create a sense of thickness using clearcoat absorption.
Adding Surface Detail: To introduce an independent layer of bump mapping - like light scratches or water droplets - that only affects the top coating and not the base material underneath.
Full-size comparison: http://corona-renderer.com/comparer/icmqPF
You can fine-tune the Clearcoat layer using several dedicated parameters:
Amount (0 to 100%): Controls the overall strength and visibility of the clear coat.
Roughness (0 to 100%): Works just like the base layer roughness, allowing you to blur the clearcoat's reflections independently.
Index of Refraction (1 to 3): Defines how strongly the clearcoat reflects light.
Bump Map: A separate bump input, so you can add surface details - like fine scratches or dust - exclusively to the top coating without affecting the base material.
Absorption Color: Allows you to tint the clearcoat, which in turn realistically colors and affects all the layers beneath it.
Examples:
As the following comparisons show, adding a clearcoat can bring a lot of visual variety and realism to your materials. One of its most powerful features is the ability to use completely separate bump maps for the base layer and the top coating.
Left Image: The wooden toy has a subtle wood bump applied to its base layer. The clearcoat is active on top, but it remains perfectly smooth with no bump map of its own.
Right Image: A strong grunge mask is plugged into the clearcoat's bump slot to simulate weathered, aging varnish. In this setup, you can see both the underlying wood grain and the worn clearcoat working together to create a highly realistic finish.
Full-size comparison: https://corona-renderer.com/comparer/UBqpXV
Clearcoat absorption can introduce a significant difference in the diffuse base of materials. In the case of an instrument like a violin, the raw unedited wood has a rough surface (Roughness amount ~ 70%) and a low IOR of 1.35, as well as a consistent bump map following its wooden texture.
Clearcoat example settings setup
Through the use of a clear coat, we can emulate a varnish/finish look on the material; with an increased clearcoat IOR of 1.4 and significantly lower roughness levels, the material now becomes more glossy. The addition of clearcoat absorption color is introduced as a form of varnish-thickness. In reality, violin coating consists of numerous coats that add up to coat thickness and darkened coloration of the underlying base.
Full-size comparison link: https://corona-renderer.com/comparer/n5b6pe
Full-size comparison link: https://corona-renderer.com/comparer/3nvVoy
Car paint is another perfect example of how the Clearcoat layer helps you achieve stunning, realistic results - all without needing to build a complex setup using the Corona Layered Material.
Just like the real-world manufacturing process, you can use the base layer as a rough, colored primer, and then apply a smooth, glossy clearcoat directly over it. From there, adjusting the clearcoat's absorption color is a great way to add deeper, richer tones to your final paint job.
Full-size comparison link: https://corona-renderer.com/comparer/d2YphT
Clearcoat absorption color can be changed to affect the base layer
Note: In cases where the clearcoat layer is weathered, this can be emulated by mapping its amount parameter. This will help introduce patchy-looking paintwork or a surface look of "skin shedding", scratches and other forms of damage, as seen in the previous examples.
Glints
Starting with Corona 15, the Corona Physical Material includes a dedicated Glints layer. This feature simulates the behavior of microscopic reflective particles - commonly referred to as "flakes" - embedded within or resting on the surface of the material. These flakes catch light at varying angles, generating high-intensity specular highlights that shift dynamically as the camera or light source moves across the surface.
While the glints effect is essential for recreating the complex, multi-layered appearance of metallic automotive paints, it is highly versatile. You can use this layer to add physically accurate sparkle to a wide variety of materials, including:
Metallic Car Paints: Simulating metal flakes, typically sitting right beneath a glossy clearcoat.
Natural Surfaces: Recreating the sparkle of fresh snow, frost, or sunlit sand.
Manufactured Goods: Building highly reflective materials like decorative foils, glittering cosmetics, or pearly plastics.
Different material examples and their settings:
Sheen
Sheen can be used to approximate the effect of subsurface scattering in microfibers for cloth-like surfaces such as velvet, satin (etc.). Layer strength can be controlled through the amount parameter, while roughness can offer further control of specular highlights or overall sheen reflectance. Sheen Color can be edited to a specific color for a more preferred visual outcome (although in reality, the sheen is exclusively white color). All of Sheen's parameters can be mapped to offer a further variation, irregularity on the applied effect.
Sheen applied on fabric. Click for a comparison http://corona-renderer.com/comparer/BoTmMV
Complex IOR for Metals
For non-metal materials (dielectrics), the way light reflects at different angles - known as the Fresnel effect - is controlled entirely by a simple Index of Refraction value. Metals, however, interact with light quite differently, and their reflection curves rely on more complex physical variables.
If you need to create a perfectly precise, physically accurate metal - like pure gold or copper - you can use the Complex IOR mode. This allows you to bypass the artistic Base and Edge Color setup and use real-world scientific data to generate an exact, true-to-life reflection.
For a detailed explanation and practical examples please navigate to the following guide: How to use Complex IOR in the CoronaPhysicalMtl?
Metals created through the use of CoronaPhysical - Complex IOR
Note: Base and edge colors should be used primarily since they offer more flexible control of the material. Using Complex IOR settings without reference values is not recommended.
Volumetric and Subsurface scattering (SSS)
Volumetric and Subsurface scattering properties can also be used within the Corona Physical Material. Volumetric scattering can only be enabled when the material has refractive properties, while Subsurface scattering (SSS) can only be used if the Refraction channel is not being used. Do note that volumetric and Subsurface scattering parameters are only enabled for Non-Metal materials.
Example of volumetric and subsurface scattering
Examples: A material like marble can benefit from using Volumetric or Subsurface scattering, with the latter being much faster to set up and to render. Below, you will find an example of a statue with Subsurface scattering and without.
Full-size comparison link: https://corona-renderer.com/comparer/srkpp5
Thin Shell (no inside)
When you enable the Thin Shell (no inside) option in General properties of a Corona Physical Material, Corona treats your 3D model as a paper-thin surface with absolutely no internal volume. Because the object is considered hollow and without thickness, this mode disables true refraction, volume effects, and subsurface scattering. Instead, refraction is handled by simple opacity, while subsurface scattering is replaced by basic diffuse and translucency.
This is the perfect setting to use when your models are built with no actual thickness. It is highly recommended for creating fast-rendering window glass, soap bubbles, or thin organic materials like tree leaves.
Example of a thin-shell leaf, assigned on a plane mesh with opacity
Presets
The Corona Physical Material comes with various presets you can choose from. These don’t include any textures, just preselected settings in the material to give you a great starting point for many common types of materials that you’ll be using in your scenes.
Most of the metallic presets are split into three categories. A brushed preset, that has a strong roughness value along with surface anisotropy that simulates a "brushed" effect on the material.
A foil preset, in order to represent a flattened mostly smooth metallic surface (very thin sheet or leaf-like material, example of a copper foil, or aluminium foil). Generally followed by low roughness values, overall more glossy surface, and smaller amounts of surface anisotropy.
And lastly rough as an in-between of foil and brushed types, with average rough values and low anisotropy.
Some of the available CoronaPhysical Mtl Presets rendered)
The dielectric (non-metal) presets are not sorted into strict categories. Instead, each one is custom-tailored to showcase the specific physical properties needed to make that exact material look realistic. Here are a few examples of how they work:
Diamond: Features a naturally high IOR and comes with dispersion already enabled and properly configured to create realistic light-splitting effects.
Architectural Glass: Builds upon the standard glass preset but adds a distinct absorption color, giving it the realistic tint often seen in large building windows.
Velvet: Recreates the soft, light-catching behavior of silk and similar fabrics by combining anisotropy with the dedicated Sheen layer.
Opaque PVC Plastic: Simulates a solid plastic base topped with a subtle, thin clearcoat (with the clearcoat amount set to 0.5) to give it a natural, glossy finish.
Other Information
You can use the Corona Converter to convert Corona Legacy Materials to Corona Physical Materials.