We now need a rubber material for the tires. A modified version of this material can be used for the rubber sealing around the doors or for the steering wheel, for example. Rubber for tires has a dark color and a slightly rough surface. This type of surface can be created using primarily the Color channel and an increased Roughness value in the Reflectance channel.
Let’s start by creating a dark color in the Color channel. Avoid using pure black and pure white when creating materials - neither is rarely, if ever, present in the real world. Also remember that the Reflectance channel will also reduce the color’s saturation. A Brightness value of about 20% is dark enough depending in part on the lighting setup. You can also add a little saturation to the color. The HSV color system should be used for this. Refer to the image below as a reference. Set Model to
To avoid the color being too monotone, the brightness can be varied in the Diffusion channel. Set its Texture to Noise and reduce its Global Scale value to 1% to create a very fine grain. Back in the Diffusion channel, enable the Affect Specular and Affect Reflection options, which will cause the intensity of the reflection and highlights to be affected by the Diffusion channel.
In the Reflectance channel, rename the layer Default Specular to Reflection and set its mix mode to Normal. For this layer we will set Type to GGX to create a soft falloff for the reflections. The width of these edges is defined using the Roughness value. Set this value to approx. 40%. Set Reflection Strength to 50% and Specular Strength to 100%. Now all you have to do is link the intensity of the reflection and highlights to the angle of view on the surface. Otherwise the effects will be too intense and will block out too much of the surface color’s shading.
In the Layer Fresnel menu, set Fresnel to Dielectric and set Preset to Pixelglas. Alternatively you can manually adjust the refraction index. The material can now be applied to the tire object Wheels.1 in the Object Manager and to the Rubber objects.