In this short tutorial, we'll see how to use the Thin Wall mode for thin object materials in Cycles, introduced in Blender 5.2.
Video Transcript
Hello everyone! In this short tutorial, we'll see how to use the Thin Wall mode for thin object materials in Cycles, introduced in Blender 5.2. This mode lets you render translucent objects such as leaves, paper, curtains, and much more in a physically accurate way.
In previous versions of Blender, rendering these kinds of objects often required solutions such as mixing the Translucency node with the Principled node, applying the Material to geometries with actual thickness, or using node setups that, in any case, did not produce physically accurate results.
With Thin Wall, instead, we can use only Principled, achieving physically accurate results while also simplifying the geometry, because we can remove its thickness, as we'll see in this tutorial.
Before moving on to the practical examples, let's take a moment to understand what Thin Wall actually does. The Blender documentation explains that a Principled BSDF node includes a base layer where we can specify whether the material is metallic, emits light, transmits light, or implements Subsurface Scattering effects. Above this layer are Thin Film, introduced in Blender 4.2, then Coat, and finally Sheen.
When we enable Thin Wall mode, the object's geometry is treated as having zero thickness, and the Thin Film, Coat, and Sheen layers are mirrored to create a sort of sandwich structure. To control the translucency of objects, we can therefore use either Transmission or Subsurface. Let's start with Transmission.
The scene you're seeing on screen was created with an earlier version of Blender. To achieve the translucent curtain effect, I connected the Texture's Alpha channel, which was semi-transparent, to the Transmission Weight input of the Principled node, after first modifying the Alpha information with an RGB Curve node. It was a solution carefully tuned to achieve a good result, but it certainly wasn't physically accurate.
In Blender 5.2, I remove everything between the Texture's Alpha output and the Principled Transmission Weight input, leaving the Transmission Weight value set to 1. This produces a uniform transparency effect generated by the Principled node and calculated according to the thickness of the curtain geometry. Setting Transmission Weight to 0 would make the curtains opaque.
After enabling Thin Wall, we immediately notice a difference in the render, which generally appears darker. As I mentioned earlier, since we're using Thin Wall and controlling its effect through Transmission Weight, this parameter must be greater than 0, although it doesn't necessarily have to be 1. At this point, however, the curtains still have thickness, while one of Thin Wall's main strengths is that it works with zero-thickness geometry.
In Edit Mode, I remove the back faces of the curtains that were providing their thickness, then switch back to the scene in Rendered mode. The final result is brighter than the previous one, better than the result obtained without Thin Wall, and the translucency can be controlled using the Transmission Weight parameter.
I'll now show you, in sequence, the result obtained with the original solution, then with Thin Wall applied to the original geometry, and finally with Thin Wall after removing the faces that gave the curtains their thickness.
We've seen how to quickly set up Thin Wall together with Transmission. Now let's see how to use it with Subsurface Scattering instead. First, I set the Transmission Weight value to 0, then I open the Subsurface section of the Principled node.
Subsurface Scattering simulates the scattering of incoming light rays, separated into their RGB components, beneath the surface of an object, producing better results for materials such as marble and organic surfaces. In Thin Wall mode, however, objects are treated as having no thickness, so the three Radius parameters are disabled. The Scale parameter and the Subsurface Scattering implementation method are also disabled.
To control the translucency effect using Subsurface Scattering, we first set Weight to 1. This produces a result that is very different from what we obtained with Transmission and now depends heavily on the Anisotropy value.
In this context, Anisotropy determines how much of the incoming light is scattered back toward the light source and how much passes through to the other side of the object. With Anisotropy set to -1, the light is scattered completely backward. Since most of the light in this scene comes from outside, setting Anisotropy to -1 makes the curtains appear almost completely black. With Anisotropy set to +1, on the other hand, the light passes through completely, making the scene even brighter.
The curtains on the left appear dark because the shutters behind them are closed. Here's how the scene looks after removing the shutters and setting the curtains' Anisotropy back to 0. All of the curtains share the same Material.
Subsurface and Transmission are therefore two different ways to control translucency with Thin Wall, but they produce very different results. Which one you choose depends on the effect you want to achieve.
Before wrapping up this tutorial, here's a small bonus. Let's also take a look at the effects produced by Thin Film, introduced earlier in Blender 4.2. Thin Film adds a subtle tint on top of the other effects calculated by Principled. More specifically, the Thickness parameter represents the wavelength of the light used to produce the tint. The default value of 0 disables the effect completely, while values between 400 and 1000 generally make it much more noticeable.
A viewport preview with a low Sample count and Denoise enabled is not the best way to appreciate the Thin Film effect, so here's a comparison between details from two renders produced with higher quality settings.
I'll conclude with a gallery of the renders created using the different settings covered in this tutorial, so you can examine them more closely.
That's all for this tutorial! If you found it helpful, you can support me by leaving a Like and subscribing to the channel. See you next time!