New material preview scene

The material preview is a vital part of blender. It is used to quickly judge material properties and tweak them without needing to create a proper lighting setup yourself. But in my opinion, it has not gotten as much love as it deserves.

There are many ways in which the current material preview could be improved upon. I have made a prototype of a new preview scene, that fixes many of the problems with the current scene. I am not proposing that this specific material preview is implemented into blender, only that some mayor overhaul should happen. However if the devs decide to take this prototype as a basis for a new preview scene, I'd feel honored. The Blendfile is at the bottom of the post.

3-Point-Lighting System

This is the current preview scene:

A common technique for lighting a scene is the Three-point lighting method. The current preview scene only has two lights. The big plane and the point light could resemble the key and fill lights, but I don't know if that was the intention. Furthermore the plane produces a big dark ugly line that is visible in the reflections of shiny materials. The new preview scene features a proper Three-point lighting setup, plus a bit of Ambient Occlusion.

Better UV Mapping

The UV Mapping in the current preview scene is a mess.

• The plane is so huge so that only a tiny section is visible. This is bad if you want to see the plain texture without distortion in its whole.
• The sphere has a UV-projection from the preview camera. No distortion of the texture is visible from the curvature of a sphere. This is not what you need if you want to see how a texture wraps around a curved object.
• The cube... Well. See the image. Its messed up. It probably never got payed attention to and was not meant to be this way.
• Suzanne's UV-Map is cut into five sections: The main body, two eyes and two ears. Matching parts are placed at different parts in the texture so that they don't really line up well.
• I have left out the hair in the pictures because a good UV-Map is not that important with hair. Apart from that the UV-Map in the current preview for hair is actually alright.

Here are the UV_Maps in the improved scene.

• The whole plane is in the frame and the UV-Map is as you would expect: X right ,Y up and (0,0) bottom left.
• The sphere is also unwrapped by a projection from a camera, but the camera is placed behind the sphere. This gives the texture a more curved look.
• The cube is unwrapped so that the texture is basically folded on the cube. Only on the top edge of the left face there is a visible seam and 3/4 of the texture is visible.
• Suzanne's eyes were connected to the rest of the mesh so that no breaks are visible. There are also no seams visible to the camera. The mesh was then unwrapped using the SLIM-Branch of Blender.

Comparison

A simple plane is useful when designing procedural textures. The plane in the current preview is only partially visible and is not even square, which stretches the texture horizontally if the generated coordinates are used. (UV-coordinates are actually undistorted.) This makes it hard to estimate the scale of features in the texture you are designing.

The new sphere is an Ico Sphere with subdivision level 6. This gives a bit more vertices to work with when trying out materials with displacement.

The new cube has a slightly beveled edges. This allows to judge the roughness of a material a lot better.

The fact that eyes of Suzanne are merged with the mesh is also useful for subsurface scattering materials such as skin.

Hair is a bit problematic on both preview scenes. The fist set of images is supposed to be blonde hair. As you can see it looks way to dark. I have tried adding a spotlight just for hair in various different positions, but it never made it any better. Not sure if its the hair shader or what. Because the grass looks just fine. If you have any idea how fix this problem, leave a comment.

Render time

I do confess. The better looks come at a cost. The render times for the new preview scene are about twice of the current one. But most of the images took about 20 seconds to render, and that at 96 samples instead of the default 16. Also the images are much bigger than you would normally have them in the GUI. So all in all, I think it would still be acceptable. Here a few factors that could contribute to the longer render times:

• The "Light Paths" settings were increased a little bit. This means that the light rays bounce of or refract through surfaces more often until they are discarded.
• The grid paper is a procedural texture that is more complicated than the current checker texture. Maybe a texture file would be faster at the cost of increased file size?
• All three of the lights are Meshes. Maybe area lights would be faster?

Everything was rendered on a GTX960

Other improvements

• The background better matches new dark 2.8 theme. It is made of black and white Graph paper which is a lot prettier than the overused checker pattern if you ask me.
• Perspective distortion is not as strong because the camera is further away.
• Sphere is actually round. Its hard to notice, but the current sphere is actually a bit like a potato:

World sphere

The World sphere is currently a sixth option among with the five shapes. It shows the sphere but instead of the room, the background is visible as it is set in the World tab in the Properties editor. This is useful if you are using an HDR-Image as background and you want to know what a material looks like in the lighting of the HDR. Unfortunately the two lights from the scene are also visible, which corrupts the light from the background. Furthermore I think that this feature should not only be an option for the sphere, but instead be a checkbox that removes the room and lights from any shape currently selected.

Eevee

The Eevee preview scene could probably be a whole other post. Because as far as I know, there isn't one. The cycles and the grease pencil previews are both under release/datafiles/ , but there does not seem to be one for Eevee. If you look at the preview while Eevee is selected as Render Engine, it looks like this:

This is the same orange materials as the one in the sphere comparison.
An Eevee preview scene is probably not as important as the cycles one, because Eevee renders so fast that you can just look at the "real thing". But can still be useful when designing a material while you have not yet setup lights and whatnot. Also it should be done just for consistency sake.

Most likely any cycles preview scene could easily adapted to Eevee by adding a Reflection Cubemap, an Irradiance Volume and doing some other tweaks. But for now, let this be a problem for another day.

Blend file

Here the new_preview_cycles_prototype.blend (CC0). It's made in Blender 2.8 , so you'll need that to open it. It contains all demo Materials, except for the stone wall, because that would increase the file size by about 27MB. The stone wall is one of the free textures on Poliigon .

You can find the current Blender 2.8 preview_cycles.blend file here .

If you have any Idea how to further improve the material preview, leave a comment. I'm more of a blender hobbyist, so there is a good chance that I missed some points.