Materials processing: the what, why and where

On August 16th, Linden Lab announced the forthcoming arrival of material processing in SL in the form of specular and normal maps. At the same time, a video was released demonstrating some of the capabilities. But what does this actually all mean for the everyday user in SL? Here’s what I hope is a lay guide to things, including comments from one of the architects of the new system, Geenz Spad, as to how it came about.

Materials Processing

This is not intended to be a technical discussion on computer graphics mapping in general or on normal or specular maps in particular. Rather, it is intended to provide a broad, non-technical explanation as to how the latter work. 

Materials processing is the combining of various computer graphics “maps” to significantly increase the level of detail that appears on any object or surface within a computer game. Within Second Life, textures (themselves a form of computer graphics map called a diffuse map) are routinely used to add the illusion of surface details to in-world objects and surfaces. The new material processing capability will introduce two further kinds of computer graphics map to SL which can be used in-world with textures to dramatically increase the detail and realism of objects and surfaces. These additional maps are called normal maps and specular maps.

Normal  Maps in a Nutshell

Normal maps (sometimes referred to as bump maps, although they are more rightly the most common form of bump map) are a means of faking high levels of detail on an otherwise bland surface by means of simulating the bumps and dips that create the detail. Normal maps can be created in several ways.

For example, when working with 3D models, a common method is to make two models of the same object: one a very complex, highly detailed model with a high polygon count, the other a much lower polygon count model with significantly less detail. An overlay process is then used to generate a normal map of the detailed model’s surface features which can be applied to the less complex model, giving it the same appearance as the highly detailed model, but for just a fraction of the polygon count, reducing the amount of intensive processing required to render it.

Using a normal map to enhance the detail on a low-polygon model. The image on the left shows a model of some 4 million triangles. The centre image shows a model with just 500 triangles. The image on the right shows the 500-triangle model with a normal map taken from the model on the left applied to it (credit: Wikipedia)

Another common way to produce a normal map is to generate it directly from a texture file. Most modern 2D and 3D graphics programs provide the means to do this, either directly or through the use of a plug-in (such as the nVidia normal map filter for Photoshop). When combined with diffuse maps, the normal map creates the impression of surface detail far greater than can be achieved through the use of the texture alone.

Normal map from a texture: left – the original texture (diffuse map) and its normal map shown as a split view; right – the material resultant from applying both maps to surfaces inside a game (credit: Valve Corporation)

Specular Maps

In the real world, every highlight we see in an object is actually the reflection of a light source. Surfaces and surface details reflect light differently to one another, depending on a range of factors (material, lighting source point(s),  etc.). Specular maps provide a means of simulating this by allowing individual pixels in an object to have different levels of brightness applied to them, giving the illusion of different levels of light being reflected by different points on the object.

When life gives you lemons: a mesh lemon with (l) a  normal map  applied, and (r) a normal and a specular map together. Note how light is apparently being reflected across the surface of the latter (credit: Mind Test Studios)

Like normal maps, specular maps can be produced in a number of ways, both within 3D graphics modelling programs and in tools like PhotoShop. As shown above, they can be combined with normal maps and textures to add detail and realism to 3D models and flat surfaces.

What Does This Mean for Second Life?

Second Life itself already includes a dynamic example of how normal and specular maps can be used: Linden Water. This is created using an animated normal map to create the wave-like effect for the water, while an animated specular map adds the highlights and reflections. The result is a very realistic simulation of moving water able to catch and reflect sunlight.

Just as the use of normal and specular maps create a very real illusion of water with Linden Water, the new materials processing capabilities will significantly enhance the look and realism of both mesh and prim content within SL. Mesh content should additionally benefit as it will be possible to produce high levels of detail on models with low polygon counts (as shown in first image in this article). This will improve rendering performance while also having the potential to lower things like land impact for in-world mesh items.

The only initial limitations as to where and how normal and specular maps can be applied is that they will not be applicable to avatar skins and system layer clothing. Any decision on whether the material processing capability should be extended to include these will depend upon at least two things:

  • Community feedback – whether there is a demand for normal and specular maps to be used with avatar skins
  • Understanding what is happening with the avatar baking process, and determining what is involved in getting the new baking process and material processing to work together.

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