Tutorial : realistic clay render with Yafray and Blender

This short tutorial is intented to explain you how to produce a realistic and useful clay render in Yafray (after having used Blender to produce a car model) For me, useful means this render will help you to find about your mesh bumps. Realistic means, your render looks like real, physical clay sculpture :

Clay render example

Foreword

When I was a newcomer in CG cars world, I’v oftenly seen a word I didn’t understand (as a non-native English reader) : clay, as in “please show us a clay render”.

Asking my favorite dictonnary, I understood that clay render refers to the clay designers use to produce physical mock-up of a concept car. It’s easy for any one to draw some curves on a paper sheet or in 3D/CAD software, but to fully define the shape it’s easier for them to work with a physical medium (e.g : curves intersections or transitionnal shapes). That is, the clay.

For us, amateurs CG artist (or confirmed or even professional), a clay render is of interest to show the defects of our 3D model. Why ? Because clay shows curvature variations well, and unsmooth variations look unnatural. Here’s an example :

Clay render example with annotations

Overview

I already told you it will be short :

  • Step 1 : create a dedicated material to represent clay
  • Step 2 : scene setup

That’s all 🙂

Step 1 : clay material

Create a new material on a dump part.

The following characteristics are the exact and complete settings I use :

  • Diffuse colour : #D6C796
  • Specular colour : #CDBE90
  • Mirror colour : #FFFFFF, useless as there is no reflection on clay 🙂
  • Diffuse shader : Lambert, Ref 0.69
  • Specular shader : CookTorr, Spec 1.135 and Hard 8
  • Mirror Transp tab : choose preset “No Reflect/Transmit”

Clay material settings

I advise you to setup your material this way, have a render with it then start only tuning it to adapt it at convenience.

Step 2 : scene setup

For my common clay renders, I do the following :

  • Duplicate all the parts constituting your model : select them using RMB for the first one then Shift+RMB for the other ones. Then Shift+DKEY, then ESCKEY not to move them.
  • Move them to another layer : MKEY to show the list of layers, select one empty layer and confirm.
  • Change to this layer.
  • Join the several parts into a single one : Ctrl+JKEY. It’s just more convenient to change material for one part than for N.
  • Change the material of this part : select the previously created “Clay”.

Now come the core scene setup (above steps were just a training) :

  • Add a white plane (or any color/material you like) under your clay model.
  • Go to Shading panel (F5KEY), “World” buttons. Change settings for a full white sky. I expect the sky not to create any artefact on the model at render time : so I use a constant lighting.
  • Go to Scene panel (F10KEY), select Yafray as rendering engine.
  • I use full x16 antialiasing (oversampling as Blender call it) : click on “OSA” and “16” buttons to activate them.
  • In “Yafray GI” tab, select “Full” as Method and “Best” as Quality. Change also EmitPwr to 1.3 to have a brighter scene.

Launch render, and stay tuned with a full bottle of coffee. On my hardware, Full/Best/OSA16 setting is so slow that I can’t stay in front of display to see render progressing.

One hour later (or two, or ten, or … depending on model complexity) here’s what I got :

Clay render example 2

2 thoughts on “Tutorial : realistic clay render with Yafray and Blender

  1. Dear Mr. Baron (I suppose that Thomas Baron is your complete name, sorry if I am wrong 😉 )

    I am very interested in realistic Renders using Blender and Yafray, but for now I consider myself a newie.

    Just I would like to say to you “Congratulations for your great blog!” because it very useful and helpful.

    Thank you for sharing your knowledge!

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