Best Parctices for Material Authoring

Material Authoring is here referred to as a technique describing how to make surface most faithful to its original. This process is complex and involves multiple moving parts.

Visual Correctness

When talking about something being correct and true to its original, we are introducing
subjectivity. This subjectivity comes from how each individual perceives such item or a surface.

On top of that, in CGI, current most spread out technology uses limited boiled
down approximation of a surface (textures) to try to get it back to look like reality.

That mixed with the fact of how the surface has been processed, what color spaces and
devices to capture and dispaly has been used, and what software tools are used - makes
for a complicated pipeline that makes it hard to definitely say what is correct.

Material authoring for Corona Renderer and black environment

Technology is evolving and there is going to be numerous novel methods of capturing and displaying surfaces more faithfully. Some of these methods are BTF capture and Neural, ML, NERF or other AI based models and approaches. These will be supplementing current tools to reach a point when the whole process is less scattered and more streamlined.

Material Authoring

Meanwhile it is possible to make a good approximative look of the material that work more or less similarly across software, when it comes to matching reality very precisely and overcoming uncanny valley (human notion of feeling something is off) - picking battles is needed.

Choosing software and environment that Is relatable to what the end goal is and material author assets for that.

Here are technical steps to make material authoring for end goal:

  1. 1. Define software and environment

    This can be for example 3Ds Max + Corona Renderer. As environment - white high key studio.

  2. 2. Acquire or create textures of surface

    This is where TMAC can be used or other methods described in Texture Acquisition Techniques

  3. 3. Take reference photography

    Create a setup that mimics choses environment lighting and take photograph of the sample there. It is important to use color checker and proper white balance. Tip: bend sample and try to get as much visual clues as possible.

  4. 4. Material Author

    Tweak textures till material in chosen software visually matches reference photography.

It is important to keep similar color and contrast profiles while doing such authoring. For example keeping neutral profile for photography and keeping neural contrast in rendering engine. Also it is vital to use high CRI (color renderin index) lighting for reference studio.

Common Visual Authoring

There is another common way to author - and that is real comparison of sample in booth to visual representation on display.

Meanwhile this practice is common, there are few disadvantages to it. First one is that lighting in the
booth is usually not switchable and is set. This light may or may not be preferred. On the flipside, many of
these booths has its digital versions calibrated and ready for numerous 3d packages.

Another disadvantage is that booths can take only surfaces up to certain size.

It is important to have professional color calibrated display and no color spill from environment
to the booth. This is also painpoint of this method as other people can have different booth
or display and can perceive colors a bit differently.

This method is color managed and more scientific.

Feel Judgement

Judgement by eye in natural environment can be beneficial to create and memorize how fabric feels and behaves. It is important though that different environments like bulb lighting or sun can color fabric differently and that shall not mislead color judgement.