How to Create Iridescent Materials with Thin Film

This tutorial covers some easy steps for creating several iridescent materials: soap bubbles, as well as pear-like soap dish and dispenser.

Overview

VRayMtl’s Thin Film layer is perfect for recreating iridescent surfaces such as soap bubbles, oil spills, lens/glass coating, reflective car paint layering, and many more. The layer produces the effect of a thin film interference on the material’s surface, making it iridescent.

VRayMtl includes a ready-made preset with a soap bubble material that significantly speeds up the building-scene time and saves you time for tweaking the Thin Film layer. For more complex surfaces such as an iridescent pearl-like surface, the Thin Film layer provides different approaches.

In this tutorial, you’ll learn how to use the Thin Film parameters to create soap bubbles and bathroom accessories' pearl-like surfaces.

The bathroom scene used here contains a simple interior (room) setting. The closeup shots are taken with a V-Ray Physical Camera (set to Physical Exposure) that uses real-world camera settings for further realism. The assets are taken from Chaos Cosmos library.

Note that the Start scenes have the DoF parameter disabled for the VRayPhysicalCameras. The final results are rendered with DoF enabled and all assets visible.

When opening the scene files, a mislocated Chaos Cosmos assets warning may pop up. Choose No for working with the assets packed in the archive and keeping consistent output with this tutorial.

To download scene files: Download Scene Files

Want to follow along but don’t have a license?: Download Free Trial

Part I: Using Soap Bubble Preset

Using a soap preset is very easy - just create a VRayMtl and assign it to a sphere geometry.

Then, in the basic parameters, select the Soap Bubble preset. There’s no more need for tweaking the material. The Soap Bubble preset values are perfect for recreating a realistic bubble surface and they are as follows:

Both Reflection and Refraction colors are set to white.
Diffuse color is black.
Thin Film IOR is set to 1.35.
Min thickness is 500.
Refraction IOR is set to 1.
Thin-wall is enabled.

Here's the render. The oily rainbow look of the soap bubbles is visible.

The VRayPhysicalCamera used here is set to Physical Exposure. The ISO is 100, the F-Number is 8, and the Shutter Speed is 15. Vignetting is also enabled and set to 3.

FoV is disabled and the Focal Length is 60.

Note that DoF is enabled and the Soap_Foam group is visible in the Thin_Film_Soap_Bubbles_End scene used for this render.

Part II: Creating Iridescent Pearl-like Shading

The toothbrush holder and the soap dispenser are opaque double-sided objects. In this part you’ll learn how to make them pearl-like with a pink tint by customizing the thin film layer. Keep in mind that this kind of a setup will look different in another lighting and environment scenario, as it is highly reflection dependent.

First, create a new VRayMtl and assign it to the toothbrush holder and the soap dispenser.
Set the Diffuse color to pink. In this particular case, rgb (245, 174, 199) is used to give the objects a pinkish color.
Change the Reflection color to white to make the material more reflective.
Lower the Reflection Glossiness to 0.85 to make the reflections blurrier.
Add a Noise texture for better control of the bumps and map it to the VRayMtl’s Bump map slot.
Set the Noise texture to Fractal and the Levels and Size to 3. Leave the rest of the parameters to their default values.
The bumps are too strong so let's reduce the Bump map multiplier to 10.

Adjust the Coat Layer

Leave the Coat color to default white and set the Coat amount to 1. Thus, the coat layer and the diffuse color will blend together.
Slightly reduce the Coat glossiness to 0.99 to make the reflections glossier and less glass-like.
Plug the same Noise texture in the Coat bump slot of the VRayMtl.
Set the Coat IOR to 2.

Adjust the Thin Film Layer

Enable the Thin Film layer from the VRayMtl parameters.
Plug another Noise map to the Thin Film Thickness map slot to pick values for the thickness from 250 to 400 based on the noise colors distribution.
Set the Noise Size to 2, the Noise Threshold High to 0.8 and Low to 0.2.
Set the Thin Film IOR to 3. The higher the value, the bigger the color spread.

Here are the soap dispenser and toothbrush holder.

The VRayPhysicalCamera used here is also set to Physical Exposure. The ISO is 100, the F-Number is 8, and the Shutter Speed is 30. Vignetting is also enabled and set to 10.

FoV is disabled and the Focal Length is 180.

Part III: Creating Iridescent Faceted Materials

In this part, you’ll learn how to control the Thin Film thickness using a V-Ray MultiSub texture.

Set the VRayMtl

Create a new VRayMtl and assign it to the soap dish geometry.
Set the Reflection and Refraction colors to white to make the material more reflective and refractive.
Lower the Reflection Glossiness to 0.98 to make the reflections blurrier.
Enable the Thin Film layer.
Disable the Fresnel IOR Lock and set Reflections IOR to 3.0 in the basic parameters.
The soap dish tiles used here are a single-sided geometry, so let’s enable the Thin-walled option from the Basic parameters rollout. This option is intended for single-surface transparent materials.

Adjust Texture and Thin Film layer

The geometry tiles have material IDs assigned to them from 1 to 7. Make sure that your geometry also has material IDs variating in the same range for its faces/polygons.

Map a VRayMultiSub texture to the VRayMtl’s Thin Film Thickness slot. Set the map to Face material ID and reduce the count to just 7 slots. The colors of the map range from light to dark gray for every ID. They are set manually with a step of ~30.
Set the Max thickness to 550 and leave the Min Thickness to its default (250).

This will assign different values from 250 to 550 nm thickness (black 250 and white 550).

Set the Thin Film IOR to 1.6.

Here's how the soap dish turned out.

The Physical Camera used here is set to Physical Exposure. The ISO is 100, the F-Number is 16, and the Shutter Speed is 15. Vignetting is also enabled and set to 3.