Using Textures to Create the Illusion of Detail
Software Used: 3ds Max and Total Textures
This particular scene was designed to utilize a recent upgrade to the Total Textures product range, namely V19 - "Destroyed and Damaged".
As this collection focuses on numerous incarnations of man-made damage, much of which has been caused by ammunition of one sort or another, I felt that a war related scene was fitting. This would enable me to use a number of the textures on offer and take full advantage of the library.
As is the usual approach for this type of project, I needed to restrict the geometric detail in order to emphasize the textures, and thought that a cliff top bunker would make a good topic. Firstly it could be made very simply and due to its function would not require any elaborate detail, and secondly it would naturally be the target of attack and hence be peppered with shell and bullet damage - the perfect criteria for my cause!
In Fig.01 you can see the base meshes used to build the scene with the three principle components that make up the actual bunker itself: the three support struts and the building to the right.
I normally establish my camera early on so I know which areas to focus on with regards to texturing. In this example there is only really one side of the distant building that concerns me, and because the key light will be above the buildings, the underside of the bunker itself will be in shadow and so not require as much attention on the texture.
During this tutorial I will show you how I have combined various photos to create detail in specific areas, and how generic textures and alpha maps can be used on less prominent sections to create the impression of detail and save time.
Texturing can be a time consuming process, especially when you take into account mapping and unwrapping, but by considering the camera angle and lighting one can minimize the time spent in this phase.
You can see from Fig.01 that the right half of each of these will be almost completely hidden from view, and so once they have been unwrapped we need only concentrate on the left side.
Fig.02 shows the base texture for the supports which, apart from the window, is made up mainly from the four images on the left. These have been color corrected to maintain a consistency. The areas outlined in green constitute the visible areas on the supports that run between the uprights above the rock. Those parts hidden by the rock are crossed in yellow and are unnecessary, hence the blank areas. These in fact could have been omitted from the template if any more texture space was required, but as this was not an issue I left them in.
In order to combine the different images it is important to first color correct them using a combination of Curves, Levels, Hue/Saturation and Color Balance.
In Fig.03 you can see the image of a worn metal that has been pasted into a wall texture. This has been adjusted using the above tools so that it roughly matches. In order to blend it in successfully choose a textured Eraser, such as the one shown, and start to reveal the texture beneath. The areas ringed in red are quite close so only need a slight adjustment, but the crossed sections need to be deleted to disguise the seam. The textured eraser avoids the trace any straight lines which are more conspicuous. I also use the Clone Stamp and Healing Brush tools to duplicate sections of the texture, both of which are useful in this instance and can add random patterns to assist the blending.
Two remaining textures that were used can be seen on the left in Fig.04. Again, these have been color corrected to match, and using the Clone Stamp and Eraser tools have been integrated with the base layer.
The two areas highlighted in red represent the facing sides of two of the supports and hence is where most of the damage and detail is focused. I have not attempted to blend in the opposite sides as these will be hidden from view, hence the seam lines.
As this scene was reasonably low poly I wanted to ensure that the bunker looked as though it was built into the rock face, reason being that any post production could reveal more of the underside, despite it being in shadow.
To avoid adding more geometry I pasted in part of the rock texture along the visible edge of the supporting wall, which you can see in Fig.05. I also added some bullet holes on the right section of the texture.
This particular building has only one face to speak of when looking at the camera view and you can see from Fig.01 that it is a simple box with just a small section of cornicing and doorway modeled in 3D.
As the main light would be in the upper left I decided that this small section of geometry would help add a much needed shadow, and the doorway was created in case an interior was included.
The texture itself provided the template for the door as I found a perfect photo in the Total Textures V19 collection and decided to use it "straight from the box", as it were. I mapped the texture onto the side of the building initially, and then cut away a doorway on the mesh to match.
You can see how the geometry has been tailored to fit the texture, as opposed to the other way around, in Fig.06. As this texture is tileable in both directions I duplicated it so that it would perfectly wraparound the edge of the building. The red line represents the edge of the texture and the green line is the corner edge of the building.
As the adjacent wall is mainly hidden it didn't matter that the texture was identical as most of it would be out of shot.
The two windows situated in the lower half exist purely as a texture with no actual geometric depth. These could also have been cut into the building but I knew these would be boarded up. As they were already darkened by a shadow I didn't feel it necessary to model them.
In Fig.07 you can see the original window image in the bottom left corner before its color correction. I have also added in some shell damage using the inherent alpha channel to select just the area of impact.
To add in a little extra detail I painted in a thin shadow (red arrow) which is absent from the original image (green arrow). You can see in the small render in the upper left how this helps to convey a little depth where there is none.
Alpha Maps instead of Volume
Camera distance and lighting conditions wield a great influence over the way we perceive a 3D scene and so it is always worth thinking about what will actually be discernable to the eye. There is little point modeling the mortar in a brick wall if it is not close enough to the camera to be noticeable. Bump and normal maps are often a more sensible and economic way of conveying such levels of detail so always bear this in mind.
A good example is the gangway between the two buildings which is composed of a flat plane (Fig.08). I initially divided it into several sections in order to face map it, but in the end used Planar mapping.
The alpha channel that accompanied the texture has been used in the Opacity slot to describe the actual walkway which is made up of thin metal strips. I opted to use more geometry where there is a greater degree of volume such as the handrails and horizontal supports (Fig.09).
You can see how this selective use of geometry vs. texture works in the final render (Fig.10).
Another section which uses exactly the same approach and texture is the platform of the lookout tower on top of the distant building (Fig.11).
In order to give it a plausible scale I simply altered the Tiling coordinates within the Material Editor. This saves any unwrapping and is a quick and effective technique for more incidental areas.
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