Building A Marble Pattern Using Fractal Noise
by David Cornette
Computer Science Department
University of Southern Maine
Faculty Advisor: Dr. Bruce MacLeod
An important technique for generating procedural textures is the use of
fractal noise. This page illustrates the how this procedure
first element of the procedure is to create a noise function.
The noise function should be smooth, and appear to be random.
should not be truly random, however, since if it were, the pattern
would change every time a new frame was rendered to the
screen. The GLSL specification calls for a built-in
facility for a noise function. However, it is up to each
to decide the specifics of the implementation. At least one
vendor does not currently implement it at all. Therefore in
cases it is necessary to use an alternative implementation.
The image to the right is a representation of what this looks like.
The next step is to repeat
the same pattern, but at a different
scale. The image to the left shows a picture of
this. This image
much like the first, but it appears to have been zoomed out, and all of
the detail is smaller. If you look closely at the lower
corner of both images, you can see the similarity. This
appears somewhat fainter. The variation between the very
parts of the second and the very brightest parts is less than
it is for the first image. This is because the value of the
noise function has
been scaled down by the same factor as the pattern was zoomed.
These steps are repeated several more times, as illustrated in the two
images below. Each of these is zoomed out more than the one
and each is also fainter. The fourth images is so zoomed out
that from a distance, it may appear to be a solid gray rectangle.
Once all of these noises at different scales have been generated, the
four images are added together, as illustrated below. The
result is the final image, which
the fractal noise pattern. Click on it to see a larger view.
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The final step is to convert the grayscale noise pattern, into the
desired colors that will make the surface look like it is made of blue
marble. This is done with a mapping, which takes every level
gray in the fractal noise pattern, and changes it to a color. The
image to the right shows this mapping. The top half shows
levels of gray, with black at the right, and white on the
The bottom half shows which color each level is mapped to. That
is, for every point in the fractal noise pattern, find the
corresponding level of gray in the top half of the image. Then
get the color below that spot in the bottom half of the mapping.
This is the color that that point has in the final pattern.
To the left is the result of this mapping. Finally,
this may be mapped on to a three dimensional model, as seen below.
Other mappings are possible as well. The next two images show a
mapping for a cloudy sky and the resulting pattern.
This mapping could represent a mossy rock.