Stone of Stenness
The Story Behind the Image
Almost 3000 years ago in Scotland a Neolithic civilization erected stone monuments. This one is part of the Stones of Stenness which is on the isle of Orkney. This was inspired by a photograph in a book titled "Minimum" by John Pawson and follows the photograph fairly faithfully.
The image is simple but its very simplicity makes it difficult. The eye is drawn to the individual details of shape and color far more so than in busy scenes where the three dimensionality of the composition provides much of the eye appeal. The rock is the central focus of attention and natural rock shapes are very difficult to model mathematically. This was carved by humans into a basic prismatic shape but weathering over the years has roughened the surfaces. It was modeled using Povray's isosurface primitive. This primitive allows you to write a mathematical function in the x, y and z coordinates such that the surface of the object is where the value of the function is zero. This is a very powerful mechanism but much more difficult to apply than simply placing boxes, cones and spheres. The basic shape of the rock came from equations for planes and 3d noise was applied to the surfaces in a trial and error process until I got the look I wanted. The basic color of the rock was created by layering several pigments on top of each other.
The clouds are created using pigments on a couple of planes. The dark storm cloud was basically a circle with some noise thrown in to fray the edges. Note also that this cloud is not of uniform color. Two shades of dark gray were combined with noise to give the cloud a more realistic appearance. A higher plane of whiter clouds was also created to place clouds at the horizon. Also a slightly gray ground fog was added to give a more realistic appearance to the horizon.
The area that was most challenging is the grass field. I started with a macro to create grass written by Gilles Tran but this was really more suited for a closeup of grass blades. When applied to a large field it was all of uniform color and height so I added several features. First the grass was allowed to be placed on top of a variable surface. Second, I allowed the color of individual grass blades to vary. Next, the distribution of grass height was made far more scewed so that there are few very long blades but lots of short ones. Finally, I created a mechanism where blade colors not only varied locally but varied also on a larger scale so that the color of the field was not uniform as one looked across it.