I remember when I first dove into hair shading in Redshift. I was staring at two render options, unsure whether to use “Render as Hair” or generate geometry using the Redshift OBJ Strands tab. To add to the confusion, I couldn’t choose between the RS Principled Hair Shader and the older RS Hair Shader. The results seemed decent, but something was off, and I couldn’t figure out why one setup gave me more realistic reflections while the other felt flat. It was only after some trial and error (and a lot of tweaking) that I finally understood the key differences between the two shaders and why one outperformed the other for realistic renders.
As CGI artists, we know that selecting the right shader can make a big difference when it comes to rendering realistic or stylized hair. If you’re using Redshift, you might be wondering why the RS Principled Hair Shader is the go-to choice over the older RS Hair Shader. I did some research on the Redshift Principled Hair documentation. In this post, we’ll break down the differences with a side-by-side comparison to help you understand the benefits of each.
Exaggerating Hair Strands for Clarity
For the first comparison, I exaggerated the width of the hair strands and reduced the hair count. This is to evaluate how both shaders behave in identical lighting conditions. While both the RS Principled Hair Shader and the older RS Hair Shader are optimized for hair and handle opacity layering well, there’s a key visual difference.
- Principled Hair Shader (left): This shader mimics a more tubular, realistic form, providing a natural cylindrical appearance to each strand.
- Older Hair Shader (middle): The older shader produces a flatter look, which may work for stylized effects. But lacks the natural depth of the principled version.
Normal Hair Width: The Reflectance Advantage
With hair at a normal width, the strengths of the RS Principled Hair Shader become more apparent.
- Natural Light Interaction: The reflectance properties of the principled shader more closely mimic how light interacts with real hair. Light transmission through the hair is softer and more realistic, providing a subtlety in shading that’s perfect for photorealistic scenes.
- Limitations of the Older Shader: While the older RS Hair Shader is still functional, it doesn’t quite replicate these nuanced light interactions. This makes it less suitable for realism-focused projects.
Diffuse Tube Geometry: A Computational Cost with Limited Returns
The far right of the comparison shows an attempt to generate tube geometry under the “Strands” OBJ tab. This method is not recommended for realistic hair shading.
- Lack of Complexity: Unlike true hair fibers, which have a cortex, medulla, and cuticle structure, this tube geometry renders as a dull, diffuse object. It lacks the light-scattering properties essential to mimicking real hair, making it appear overly simplified and computationally expensive.
- Optimized Shading: The RS Principled Hair Shader alone is far better suited for realistic hair shading. This removes the need to generate tube geometry which doesn’t capture the complexity of real hair’s structure.
Conclusion: RS Principled Hair Shader vs. RS Hair Shader
While the older RS Hair Shader can still serve for stylized looks, the RS Principled Hair Shader is the clear winner when it comes to realism. Its ability to capture natural light reflections makes it the better choice for most projects. Avoid computationally expensive alternatives like tube geometry, as they don’t account for the true physical properties of hair.
Have any questions about Redshift hair shading? Reach out to me directly on Instagram @ronald_fong!
