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C00002 00002 4.3 Representation of a Geometric Mental Universe.
C00005 00003 MEMORY - TOP LEVEL GEM STRUCTURE.
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4.3 Representation of a Geometric Mental Universe.
At the top of the data structure is a single universe node
from which everything else can be reached. Immediately below the
universe node is a ring of world models. A robot dealing with
physical world sensor input, such as video data, has one of its world
models dedicated to simulating the immediate here and now; this
mental world is called the reality world model. In addition to the
reality world, a robot may have fantasy world models for problem
solving, planning or for recalling platonic object prototypes. In the
following, a two world mental universe will be the most common, with
the reality world being referred to as a "map" and the fantasy world
being referred to as a "dictionary".
Geometric world models have four basic kinds of nodes:
body, face, edge and vertex. The face, edge and vertex nodes are used
to form polyhedrons which may be attached to body nodes. Body nodes
in turn are connected to each other in rings and trees to form a
world model. Additional kinds of nodes discribe cameras and light
sources as well as temporary data such as shadows, spines, and
trajectories.
The image data structure presented in this section is a
computer's internal notation for what is vulgarly called a line
drawing; the common term is misleading because it does not suggest
the equally important space between the lines; terms closer to the
idea would be "mosaic drawing" or "stained glass window drawing".
The data structure has main levels: TV raster, video
intensity contour, arc contour, and region-edge.
MEMORY - TOP LEVEL GEM STRUCTURE.
The top level of the GEM data structure is constructed out
of six kinds of nodes: UNIVERSE, WORLD, IMAGE, WINDOW, CAMERA and
LAMP; by way of contrast the polyhedron data structure consists of
BODY, FACE, EDGE, and VERTEX nodes; and the auxillary nodes are
classified as EMPTY, FRAME, XNODE, YNODE and ZNODE. Initially there
is no image node and only one Universe, World, Window, Camera and
Lamp Node. The approximate interconnections of the nodes is:
←← UNIVERSE →→
/ ↓ \
/ empty nodes \
worlds displays
↓ ↓
↓ windows
↓ ↓
lamps ←←←← WORLD →→→→ cameras ←←←← WINDOW
↓ ↓ ↓
LAMP ↓ CAMERA
↓ / \
↓ synthetic perceived
↓ images images
↓ ↓ ↓
↓ ↓ ↓
↓ ↓ ↓
3-D bodies 2-D bodies
↓ ↓
faces, edges and vertices.
Now for the casual definitions of the SIX top nodes. The
Universe node is unique and all nodes are connected to it so that it
serves as an OBLIST node. The GEM universe is the mental universe or
universe of discourse for geometric modeling. Immediately below the
universe node is a ring of world nodes and a ring or displays (and a
list of empty nodes). A world node is for representing one physics
like world at a particular moment in time; three kinds of worlds
might include a perceived here-and-now world or map; a desired or
goal world; and a world of prototype platonic forms, or dictionary
world. The world points immediately at a ring of light sources
(lamps), a ring of physical camera models, and a ring of bodies.