"Visual routines", as defined by Shimon Ullman (1984), are a set of
elementary operations thought to underlie early stages of processing
in the mammalian visual system. Many other writers have adopted the
term, often using it to refer to low-level primitives in machine
vision. It is in this sense that we use it in Tekkotsu.
Tekkotsu visual routines provide operations such as connected
components labeling, region intersection or merge, neighbor-sum,
flood-fill, and bounded distance computation. Their design has been
influenced by the work of James Mahoney on visual routines when he was
at Xerox PARC (see Forbus et al. paper below.)
The set of primitives is easily extensible, The basic data structure
is the "sketch", which holds a 2D array of pixels of a specified type.
Sketch objects are actually smart pointers. Internal functions handle
all storage allocation and reference counting chores, and the usual
arithmetic and logical operators are overloaded to operate on sketches
in an intuitive way.
Tekkotsu actually takes a "dual coding" approach to representation.
The term comes from the work of the psychologist Alan Paivio on mental
representations. "Sketches" provide an iconic code, while "shapes"
provide a symbolic one. Paivio argued that people use both kinds of
representations, and when necessary, convert between one and the
other. In Tekkotsu, sketches exist in a "sketch space" and shapes in
an associated "shape space". Extraction-operators can extract shapes
(such as lines or ellipses) from sketches, while rendering operators
produce a sketch from a shape.
There are several sketch space/shape space pairs built in to Tekkotsu.
The most basic is camera space, which corresponds directly to camera
coordinates. Local space is based on egocentric (body-based)
coordinates, and world space is based on allocentric (world)
coordinates. A tool called the SketchGUI, which can be launched from
the ControllerGUI, allows you to remotely examine any of these spaces
and see the sketches and shapes that populate them.
Where to Find the Documentation
The dual-coding vision component of Tekkotsu lives in a namespace
called DualCoding, which has separate online documentation from the
main Tekkotsu system. From the Tekkotsu home page, click on
"Reference" to reach the online documentation. The, under "Library
Sub-Documentation", click on DualCoding.
Visual Routines Table of Contents
The following topics are covered in the Visual Routines chapter of this tutorial:
