The black area refers to the rusted area beneath the panels. The actual panels that have started peeling off can be seen down the right-hand side of the texture and were taken from a texture I made for a previous scene.
I used this texture in conjunction with an Arch&Design material, hence the different hue in the render. I wanted this structure to stand out in a similar way to the floating tower in my concept, as well as lending it a more metallic quality.
The rusted area did not really require any unwrapping and so I applied a generic rusted metal that was then combined with an overlay to add variation. Fig.06 shows the material with the base texture (metal19 from Total Textures V2:R2 - Aged & Stressed
) tiled in order to achieve a correct scale.
Because of the lighting and camera position in the scene it meant I was able to minimize the amount of unwrapping. For me unwrapping is a process that is best reserved for detailed areas or sections of geometry that are more conspicuous.
In this particular scene there are numerous areas that employ a box or planar map depending on their shape and volume. These bypass any unwrapping and use tileable textures that can form part of a composite map or be used on their own.
Fig.07 highlights some areas that use this technique either because of their relative size in the scene or their visibility. The wooden slats in the upper left are inconspicuous enough to get away with a single wooden texture that is tiled by a value of 2.0, whilst the sections in shadow on the right could escape with a similar treatment. Of course this approach suits stills primarily, but the rule of thumb is that a camera and lighting can be used to gauge the priority of the textures.
Elements such as the wires and cables can be done using renderable splines and can then be box mapped. The texture stretching can be controlled in either the UVW Mapping modifier or the Material Editor.
To see more by Richard Tilbury, check out Digital Painting Techniques: Volume 4
Digital Painting Techniques: Volume 5
Digital Painting Techniques: Volume 7
Beginner's Guide to Digital Painting in Photoshop Elements
Beginner's Guide to Digital Painting in Photoshop
Photoshop for 3D Artists
and Prime - The Definitive Digital Art Collection