Materials in Corona (Part.1)

We have our scene in place and we need to start playing with materials. Some assets will have their materials already preconfigured, some others will need to be tweaked to match the desired composition and others will require a fresh new one from scratch. Let’s have a look to see what we normally do within Corona.

This is the Part 1 of 3 Posts.

Point 1: Material Editor and some Basic Options

The first thing we need to do is to open the Material Editor which you can find in the below icon. We have used an sphere to illustrate the application of the material. It just requires dragging one of the default materials (grey color) to the asset you want to dress.

Within the Basic Options of each material we can find these common sections:

At the time to define these characteristics we need to bear in mind that in this field we are going to find two big groups of materials, Metals and Non-Metals. Understanding this will help us to mimic the behavior’s of the materials when affected by light. No-Metals absorb a percentage of light (refraction) and do not have a reflection colour (always white: 255,255,255 as RGB) on the other hand Metals reflect all the light and their color will be defined by the reflection color and not by the Diffuse color.

These are some of the basic features we can find in Corona Materials and also in most of the renders out there…

DIFFUSE:

Level: This is the famous Albedo…in Corona Documentation is defined shortly as the overall brightness of an object (Each material component is calculated as LEVEL * COLOR (with 255 = albedo 1)). Some artists consider (for non-metallic) having it as 0.8 whether any of the RGB color parameters are higher than 180, and leave them to 1 if lower. Chaos shows a clear example to get this clear in this link: What is Albedo? – Chaos Help Center. For metallic this parameter will be zero.

Color: The color of the object for Non-Metal materials.

Translucency Fraction: Index that serves to create translucent materials. based on the percentage the light will get deeper and scattered.

Translucency Color: The color emitted by the scattered light.

REFLECTION:

Level: This is recommended to be 1 from Corona based on PBR guidelines for Metalic and Non-Metalic materials.

Color: White color for non-metal materials and a specific one for metals.

Glossiness: Lower levels will scatter the light making it more mate, and higher values glossier.

Fresnel IOR: (From Chaos Documentation): The IOR value is available for metals and 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 (e.g. the index of refraction of air is normally around 1.0003), while for example, a value of 1.52 IOR can be suitable for generic glass materials…and 1.6 for most of the non-metallic materials. The metal ones would require values between 4 to 50.

Anisotropy/ Amount: Based in the Corona Forums: It is typically used to simulate mesoscopic details and it will be used to simulate metals that tend to break in a single direction, crystals that change colors based on rotation…

Anisotropy/ Rotation: Defining the rotation of the effect commented above.

REFRACTION:

Level: The level of resistance for the light to pass through that bends when tries to cross the material. For glass, this will get 1 as the value.

Color: Tones the light leaves when scattered.

Glossiness: This is recommended to be 1 from Corona based on PBR guidelines.

IOR: (From Chaos Documentation): 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 (f.e. the index of refraction of air is normally around 1.0003), while for example, a value of 1.52 IOR can be suitable for generic glass materials.

Generic-glass (impure) 1.52 IOR, flint-glass pure 1.62 IOR, lead-glass (crystal) 1.8.

Dispersion/ Enabled: Some refractive materials change the direction in which light travels inside them by a different amount depending on the wavelength of the light. This is called dispersion and creates a rainbow effect inside the material. Enabling it adds realism to gemstones, glass, water, other liquids, and other materials. (Source: Corona Documentation).

Dispersion/ Abbe Number: It controls how strong the dispersion effect is. Values between 30 and 60 should be used for the most realistic materials.

Thin (no refraction): This will convert a solid chunk of a solid glass object into a delicate object made of a thin layer of glass.

Caustics (slow): Used to get the patterns of light and color that occur when light rays are reflected or refracted from a surface. For instance, the light effect we see when the sun hits water in a pool that is moving.

OPACITY:

Level: This can be used to make a material transparent, but not refractive. If we apply 0 here (min value), our object will disappear from the scene.

Color: It will bring some color brightness in some white reflections. This feature is more used with maps where it will remain while the object vanishes.

DISPLACEMENT:

Displacement: In this area (Texture Field) we add our Displacement Mapt that will bring the high-definition detail of our low poly meshes.

Basic Features for Metal, Plastic and Glass:

The above picture reflects a sample of the characteristics of a glossy plastic where we select Diffuse Color as the material color, the Glossiness to its maximum and the IOR as 1.52-1.6. The Refraction we leave disabled.

The above picture sets the properties of gold material (metal), where the Diffuse Level will be zero, the Reflection will be its maximum and the color will be set within this section where we also define glossiness and Fresnel IOR which can be good at any value between 50 to 999 for metals.

The above picture sets the properties for glass material, where the Diffuse Level is zero, therefore the Diffuse color is not used.

On Reflection Level, we set it to its maximum (1), color is white, Glossiness also to 1, Fresnel IOR 1.52 (recommended for glass) and Refraction Level to 1. In case we need to color the glass, the Refraction Color is the one to use.

The final result seems to be a solid glass ball.

Our windows will require to be thinner, therefore we use the “Thin (no refraction)” feature to achieve this thin glass layer.

These previous glass configurations will not attend to how thick or thin the model is. This material will be even all along.

We assigned this to our armchair with a bit of light pink color on the Refraction Color and it seems methacrylate rather than glass… as it does not obey how light normally behaves when goes through thick portions of it.

In case we want to get this corrected we need to configure the Volumetrics and SSS section (the above picture keeps the default values where Distance is 0 therefore does not apply).

Now we add Absorption color in the line of the Refraction color but more saturated plus the Distance to 50mm. A lower distance will make the material darker. The mode will be Volumetric scattering which is the one to go for translucent, liquids, fog, and smoke materials whilst the SSS is better for skin or marble as the material tends to be opaque.

The feel is now more realistic as we can see coherence between thinner or thicker parts, as the glass darkens when becomes thicker.

Point 2: Texture Time!

Time to know how to apply our Textures to our assets with Corona.

Firstly apply a Default Material to your Asset by just dragging it.

Secondly, we add the Color texture of our material by clicking the right side button of Diffuse-Color. This button opens the Material/ Map Browser, once her select Corona> CoronaBitmap.

The Browse Image will pop up… then just we need to select the Color image from our material. In some PBR you will find Diff/ Diffuse/ Albedo/ Diffuse Color file names instead of Color…but they are basically the same.

The Corona Bitmap Properties panel appears in our Material Editor. If we need to go back to the main material features (Diffuse, Reflection, Refraction…) just we need to click on the green icon “Go to Parent” and if we want to see the new Color applied over our asset just toggle the yellow one “Show Shaded Material in Viewport“.

The materials normally come with different maps and it is good to know where to apply each of them.

In the material we use, by the way it comes from https://ambientcg.com/ (Web with many free PBR materials), has the below maps and we added the place where they should go…

Displacement.png >> This Map should go into Displacement > Texture
Normal.png >> This Map should go into Maps > Bump
Roughness.png >> This Map should go into Reflection > Glossiness Map

Before to start assigning these guys we are going to apply over our asset a UV Tile controller (UVW Map) from the Modifier List with the intention to control the size, direction and repetition of the texture tiles. Ensure the textures are not stretched or compressed too much and also they do not become repetitive, it would bee good if you can achieve seamless textures to avoid the pattern effect.

We assigned all our material maps in the right sections and now we need to play with the amount of the map strength. The way to do this is by going at the bottom of the properties panel to manipulate them (Maps) through the Amount toggle.

Remember that by reducing the percentage, decreases the effect from the map but releases the base effect of the feature.

The material we used for the below sample was “Rocks006_4K” just to play with Displacement and Bump overall.

In order to get a better surface profile we had to set a 20% Bump and 13.0 mm as Max level Displacement. The Reflection and Color were driven entirely with the Roughness and Diffuse Map respectively.