Material tutorial Blender

For this material breakdown I chose a gold material based on the material I used in my crown project.

The goal is to make a gold material, which can be seen on old jewellery exhibiting some worn look and is not the typically clean shiny gold look you get with modern jewellery.

One remark before I start: Its important when developing a material, that you use a model for preview, which resembles the final object. Just using a simple sphere or a plane will most certainly lead to longer development cycles. The lighting shouldn’t be too simple too. Just using a single point or meshlight will not suffice for the most materials, which exhibit some sort of reflection.

My sample scene for this breakdown uses a very simple broad bracelet and I use 3 meshlights to light the scene.

Selecting the base material

The immediate idea is of course to use luxrender’s metal material with the built-in gold setting. If we use it we get the following image

Besides setting the roughness, there are no parameters to fine tune the actual color texture. The metal material gives too light a result for our intended purpose. The roughness is quite ok though.

This leaves us with the next basic material type – shiny metal. This material has two channels: reflection and specularity, both fully configurable with textures. Lets assign a quick yellow color for both channels, set the roughness to 25 and see what we get.

Now that’s not really what we are aiming for. Its too shiny (as the material’s name already suggests). What we have here is in effect a compound material. Reflection as well as specularity is a reflection of light, where specularity has the additional benefit of a roughness parameter. Lets see a close-up of the above render

Using both reflection and specularity results in a rough material which seems to be coated by some shiny substance. The reflection channel is always perfectly smooth, so as long as we use it, we will always end up with a smooth shiny surface. The solution is to turn off the reflection by setting it to 0. With the roughness value we should have all the control we need to describe the material.

See below for the same shiny metal material with reflection turned off and using different roughness settings.

To be honest, I cannot image a situation, where I could make use of the compound nature the shiny metal is delivering, because in the end it will collide with the material setup I have in mind, but who knows what time will bring …

Defining the basic color

Now that the reflection issue is solved we have to concentrate on the basic color for our gold. This sounds trivial but I will spend quite some time on this topic.

The simple approach is of course to directly assign a color to the specular channel. For this project I won’t use this approach, but will rather concentrate on the gaussian texture. So its good to look at what this gaussian really is.

A gaussian offers the following controls

You have a wavelength slider, which is conveniently placed under a spectrum image, so you won’t have to guess which color belongs to a wavelength. The whole visible spectrum is available.

This texture produces a wavelength distribution in a gaussian bell curve, the maximum being the selected wavelength. The width parameter sets the standard deviation of the bell curve, thus actually telling luxrender how many wavelengths left and right from the maximum are to be used. This now sounds very theoretical, so the best is to actually visualize it