Generic Textures and Composite Maps
For objects with a relatively small surface area - or indeed any sections that take up a small part of the scene, either in the middle distance or background - we can avoid the complexity of Unwrapping.
Two such elements are the siren and lookout tower highlighted in white in Fig.12.
These could be fully mapped/un-wrapped, but when considering their distance from the camera, the bright backdrop and their rather delicate and unsubstantial structure, it would prove unnecessary.
A quick and effective remedy is to Box map it, which will avoid any obvious stretching along the three axes and mean that it can be mapped as a single section. The important factor is to ensure the Length, Width and Height dimensions are consistent, as seen on the right panel in Fig.13.
Once done it is possible to use tileable maps and combine these in a Composite material. In Fig.14 you can see that the lookout tower takes advantage of two tileable maps, the base layer being set to Normal mode and Layer 2 set to Soft Light.
These two layers work exactly as they would in Photoshop when one is placed over the other with the corresponding Blending Mode (Fig.15).
The advantage of using composite textures is that each can be controlled independently with regards to their co-ordinates, and so once applied they can be repositioned.
You can add a number of these maps into the material and tweak the coordinates to help localize detail. For example, why not apply a dirt map set to Multiply and alter the U and V Offset values to have it appear under an overhang or base of an object? To disguise a tileable texture one could overlay a map with the Tile function disabled on both the U and V axes and the Blending Mode set to Overlay.
There are a number of solutions, but this type of material enables the combination of multiple generic, textures providing the ability to position each independently, without the headache of lengthy unwrapping.
Fig.16 shows the final lookout tower which uses just the two tileable textures seen in Fig.15 and creates the illusion of detail where there is precious little.
I hope in this short tutorial I have been able to throw some light on a few of the issues to consider when texturing your 3D scenes. All elements of 3D are interrelated, and the way we perceive anything depends on a number of factors, in particular the lighting conditions.
I always try to categorize my scenes into areas of importance and usually pay more attention to those sections that are more prominent and noticeable. If you can adopt different approaches to texturing that reflect these concerns then it will help you focus your attention on what is most crucial and prioritize your time.
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