Keeping it Natural

Some of the hardest parts of any model to make look right are the sections where nature has left its mark. Weathering, erosion, vegetation or other random effects, like the results of an explosion, seem to be difficult to reproduce in a way that looks natural. There is a very good reason why this is the case – it is your brain!

The human brain has evolved to recognise patterns. Even when there are no actual patterns visible, your brain tries to make them up. Don’t believe me? I bet you have looked at staining on a wall, or a similar random shape, and thought, “That looks just like a …” - and it gets worse.

Your brain is so good at detecting patterns, and putting names to them, that you can view an infinite number of different objects of various shapes, sizes and colours, and happily label them all as “a tree”. So, you have seen millions of trees, you should be able to draw one, shouldn’t you? Give it a go – get a sheet of paper and draw a tree from memory. Provided you didn’t cheat, you have probably drawn a lollipop shape, unless it is near Christmas, in which case you may have drawn a triangle with a stem. Your brain is quite happy to accept this very crude symbol as being a tree, even though it looks nothing much a real one, and this is the crux of the problem – your brain is very bad at making random arrangements – it tries to put patterns into everything.

Nature, by contrast, seems to work in a much more random fashion. Although there are many genetic and environmental rules for how a plant grows, the chaos effect ensures that no two will ever look exactly alike. Different rules may apply, but most other natural processes work along similar lines – erosion of rocks in a cliff face, veining in marble, patches of lichen and moss, graining in timber. All these “patterns” exhibit a form of chaotic behaviour which is governed by rules so intricate, that the results appear to be more or less accidental.

Reference

There are a couple of ways to prevent your brain from creating structures and patterns that look man-made. The first of these is to use reference material: finding real-world examples of marble, trees, cliff faces, ruins or whatever, and using these as a basis for your model. You should be able to find plenty of suitable images on the internet for this purpose, although taking your own pictures will give you a library of your own high-resolution images to browse. For certain applications, the best option will be to buy a book: aerial photographs of landscapes, for example, would be difficult to take yourself.

The images below are of a gravestone covered in different lichens and mosses, and the model I created using the image as a reference. 

   

 

Randomising

The second method is to use a procedure which randomises the results in some way. There are different ways to go about this for different applications. As a first example, consider that you are colouring the blocks in a wall in slightly different shades to give a random appearance, as in the image below.

  

To help with random paint schemes for walls, floors and roofs, I have created a series of online tools which generate  Randomised Images

Some example output images from the random generators:

However, instead of using a specific picture as a reference, you could mix six slightly different shades of colour and number them. You could then use a randomiser (six-sided die) to select the shade for each block. This will give you truly random results, whereas if you choose the colours you will be influenced by your brain’s liking for evenly spread blocks of colour.

Another “random” effect can be achieved by stippling or sponging paint. This procedure is used heavily in my techniques for creating marble and granite. Whilst you choose where to stipple to some extent, the actual blobs of paint left are in a semi-random pattern, which is perfect for these types of texture.

A useful method for rubble, bushes and other "occasional" features, is to drop it from a short way above the model, and glue it where it lands. If using this technique for rubble, start with the largest blocks first, let them set, and gradually progress through to the smallest pieces. Sand can be added as a last step, and then sprayed with a 50/50 water/PVA mixture to stick it into position.