A clay render is an effective solution to show a model, and especially its topology. Every object of the scene is untextured and is defined by only one material: a warm grey matte, which remind clay. The result is a monochromic picture. The clay render is often used by 3D artists specialized in modeling or sculpting, with still frames or turntable animations.
You can enable Clay render with all the Lighting methods but it's often used in conjonction with Ambient Occlusion in Direct Lighting. With Yafaray just press the button Clay Render in the render settings.
Clay render makes all the materials look the same, but the properties of all the other elements (camera, lights, environment, volume, etc) are not affected.
Of course, you need light sources in order to see your scene: lamps, ambient occlusion, skylight, mesh lights, etc, because Clay Render is not a method of lighting in itself. Clay render with Ambient Occlusion only, provides an homogenic render, a bit dull though. This type of render can be useful for compositing.
A classical Clay Render with Direct Lighting. No lamps, just Ambient Occlusion (the color is a medium grey), with a Sunsky Background. For more informations on Ambient Occlusion chek the documentation here
The AO settings
With a simple sun, and a colored AO you can add a different mood to the picture, here a late afternoon:
The sun here has a yellowish color, 32 samples and an angle of 5 to have software shadows. The Ambient Occlusion is a medium grey slightly tinted in blue.
It gives blue colored shadows. The sun brings an interesting lighting, and the mood is very different than the first picture, but it's still a clay render.
It's possible to use a diiferent method of lighting, with GI to have subtle bouces of lights, while keeping a clay aspect. Here with Photon Mapping method (Final Gather, Use background).
Make a turntable animation
A turntable animation is a common way to show a model precisely. The animation is simple: the model turns on itself in order to see all of its geometry. The clay render is useful in this situation because it emphasizes the worque on the model, and not on its texture.
There are different methods to make this kind of animation. An easy and effective way to make a turntable animation is to use a null object (called Empty in Blender).
In the 3D view of Blender, add the empty at the origin, and parent all the objects you want to rotate, to the empty.
The camera and lights are static, you just have to rotate the Empty on itself (360 degrees on Z axis during 101 frames for instance).
For a linear rotation, select the Empty, open an IPO window. Here is the curve of the Z rotation of the empty.
Select this curve and go in edit mode, and choose a Vector handle type in the Point Menu.
To render this animation with Yafaray, choose a directory in the Output panel of the render settings of Blender. Bak in Yafaray, chek your render settings and press the Render Animation button. (You can cancel the animation with Esc now).Yafaray renders animations in image sequences (in .png or .exr). You can use Blender's video sequence editor to make a video from this image sequence.
Here is an example of a turntable animation with a clay render, and the blend file slightly simplified.