InSpeck Glossary of
Terms
2.5D
(Data in…) Data in which the three dimensions are not represented in a
homogeneous way. The depth (Z) is
always functional, for every point in
the XY graph there is at
maximum one Z notation.
X and Y are non-functional.
The best example is an image in pseudo colours used in
FAPS.
Unscientific
term but much used in the field.
Often to define the results of optical censers providing 3D data of a scene viewed from
a specific angle. The results of
the measurements of a cup measured from the front will not show its hollowness. 2.5D differentiate from a 3D model which shows the real
form of the object from any angle.
1.
Image
containing the information in Z.
2.
2D
display of a model with the
possibility to manipulate the
model.
3.
Stereoscopic
display of a model with or without the possibility of manipulating the model.
The
fabrication procedure of a model, consists
in many image acquisitions:
calculation of 3D data, a
generation of many patches,
registration of patches, fusion of patches, fusion of
textures.
Term
to be avoided because we cannot acquire a model. We can only acquire an image and make a
model of an object, a face, or of a person. Perhaps we could use the term
"Creation of a 3D model".
Parametric
function built by the summation of polynomes connected by knots. The polynoms
are calculated by recurring equations.
A B-Spline surface in 3D is obtained by calculating 2D curves along two
different directions, but in accordance with a set of common
parameters.
Straight
line stemming from the summit of an angle dividing the last into two equal angles. It's the symmetric axe of the
angle.
Procedure
that determines the relation within
the predefined domain of validity, between the notations measured by a device
and the real notations in the standard unit of measure. In our case, this step transforms
perspective geometry into Euclidian geometry. We will often will measure an
object or a pattern of which the measures are known (standard of measure) to
determine this relation. It is
sufficient that the standard measurements
are ten times more precise than the measurements than uncertainty than
the calibrating device. It is also
known that calibration is valid only within the device, for in practise the extrapolations are
not reliable.
Calibre
in the form of a flat surface.
Since in theory the form of a calibre has no importance ( except in
pathologic cases) we often use calibre of a simple
geometric form as a plan for example.
Same
thing as volume digitizing , but in
the context of the procedure of
standard measurement of the device.
It's the volume used to take the standard measures of the
device.
q
Capturor
(Normal Field)
q
Capturor
CF (Close Field)
q
Capturor
SCF (Small Close Field)
q
Capturor
LF (Large Field)
q
Capturor
SF (Small Field)
Representation
of a surface in 3D space, consisting very simply of a series of vertex. The vertices are not connected to form
polygons, and are not necessarily a known structure.
From
a cloud of points measured by a digitizer, the relation between the different
points in the space must be determined.
For example, the object can be described with triangles (three points)
that consist of 2 points, to create
a model.
Acquisition
of data with a digitizer, i.e. a
device that transforms an analogue notation into a numeric notation. In our case, it's the action of using a
Capturor to obtain a 3D image.
NURBS
(Non-Uniform Rational B-Spline)
Parametric
curve formed by the division of two weighed summations of B-Spline, and which the
para metrication in not necessarily
uniform. One NURBS surface in 3D is
obtained by calculating 2D curves along two different directions, but according
to a group of common
parameters.
Double
Field, InSpeck product, Capturor with two objectives, that permit the
choice of the visual
field.
Volume
in which 3D measures can be taken with a digitizing
device.
1.
Geometry
representing the world as it is with the same measures (e.g. mm) and the same
angles.
2.
Geometry
preserving the absolute measures and having 6 degrees of liberty for
transformations, 3 for rotations and 3 for the
translation.
In
analogy with the 3D image a 3D film would be a film containing depth
information, which would permit the
spectator to place himself anywhere
in the scene. An animated model
could be called a 3D film.
The
control software of a mechanism. Often stocked in a ROM and loaded when turned on.
InSpeck
product. Measuring system for the production of full human body 3D models.
A
geometry describes entities (points, lines, bodies, angles…), some properties (collinear,
perpendicular,…) and transformations on these entities. An important aspect of
geometries is the invariable.
Invariables are the properties that are not influenced by the
transformations of this geometry. The different geometries differentiate from one another by the
invariables and the number of
transformations available.
The
world is often perceived as a 3D Euclidian
space. That is why the Euclidian geometry seems appropriate to
describe the world. In certain
cases it isn't possible or
desirable to use the entire
Euclidian geometry of the 3D space.
We could also work with
projective geometry, that is less structured and for this reason
simpler. Intermediate layers are formed by the affine geometry and
the metric geometry. These
structures can be seen as different geometric "strata" (pl. of stratum, which
means layers), which can be
superimposed to the world. The
simplest being projective and affine, then metric and finally the Euclidian structure. (M. Pollefeys,
3D modelling from images", 3D in 2001?)
Taking
an image ( bmp, jpeg, etc ) with a camera.
Not to be confused with acquisition of a 3D
model.
Procedure
allowing the application of a 2D image on a 3D model. Different approaches can be used to
project the texture on the on the model (cylindrical, cubic, spherical, …). Furthermore, most software and 3D engines also permit defining the
application of the texture by specifying the texture co-ordinates (u,v) for each
vertex once the projection has been done.
Representation
of a surface in 3D space, consisting of vertex connected to one another to form
polygons. No supposition is made on
the distribution of the vertex and the polygons are typically consist of 3 or 4
vertices.
Science
of measure. Domain of the
technologies and instruments of measure.
3D
Entity that can represent a part or the whole of an object. The representation
can as well be done by a patch, a mesh, a parametric
surface, etc and can include a
texture.
Shifting
the summits (vertices) of a model with time with the purpose to create an animated or dynamic
model.
Procedure
that permits the creation of a 3D model of an object from many 3D models each representing a part of the object, acquired according
to different angles or even from a different model. (Ex:
head or hands at high resolution with a human body at low
resolution).
Procedure by which the vertices of a first model are progressively shifted so that it becomes identical to a second model. This technique implies that the starting model and the final model have the same polygonal structure
(same amount of vertices, same amount of
polygons and a similar distribution of its
elements.)
Careful, not to be confounded with the 3D morph
function of EM
(EditorMerger). These allow
the deformation of a model (solely the position of de vertices) to give it a
form similar to another model from which the polygon structure can differ. Following this deformation we can then
create morphing effects between the original model and the original deformed
model since they are obviously the
same structure.
Data
transfer file between FAPS and EM.
Proprietary format of InSpeck.
The
measurement is taken by a harmonic function. The results are ambiguous at a 2PI factor.
Knowing the order of a point we obtain an absolute result. The order gives the amount of periods
according to a reference plan.
Is
said of a 3D object that has polygon curves (NURBS) and that estimates well the
organic forms (a head for example).
Way to describe a 3D surface. A patch is a matrix of 3D points and the relation between the points is defined by their position in the matrix (number of lines and a fixed number of columns) having said that, a patch cannot define a closed surface. It is not like a mesh, or a meshing where we describe the relation between different points while describing an order of polygons.
FAPS
produce a patch for each view each digitizer by exporting into a .net. format. In our case, this patch represents a
part of the digitized object. A
patch is a model. The patch
corresponds well to the representation of data obtained from an InSpeck
digitizer since for each pixel of the camera's matrix we obtain a notation in XYZ. Many patches of an object can be
reunited to form a model. This
definition of patch is specific to InSpeck.
Note:
The terms Patch and Mesh do not designate the same realities in the CAD
(engineering) and computer graphics domain.
Geometric
area of nil dimension represented in
R2 space by its co-ordinates (x,y) and in R3 space by its co-ordinates
(x,y,z).
Procedure
that consists in placing numerous models representing different angles of an object, in such a
manner as to reproduce the whole of the object.
Procedure
that consists in applying transformations on partial models to place the parts in a system of common
co-ordinates.
Approximate representation of a function by the sum
of many polynomials.
·
Stereoscopic
film ( or stereo film)
Two films, one of which is presented to the right eye of the spectator and the other to the left eye of the spectator. These are the same techniques as those used for the stereo film. See also "stereo images".
·
Stereoscopic
image (also: Stereo image)
It
consists in fact of two images, one of which is presented the right eye and the
other is presented the left eye.
There are different techniques
to assure that each eye sees only the image that is destined to it
(Colour filters, polarisation filters, glasses with LCD shutters, 2
independent LCD in the helmets of virtual
reality,…). The 3D effect is
generated by our own brain. It
suffices to acquire two images with two cameras, which have parallel optic axes and that are found at the interoculare distance
(»2
inches) at the moment the
images are acquired.
Target
that permits having a referential common to all the digitizers that are looking
at the same scene. The fact of
having a common referential permits placing the different views of one object at
the right place.
Virtual
Target: Theoretic description of a real target. In the computer….
Real
Target: Target as fabricated (real object, in
aluminium…)
Rectangular
tabulation (Index/tabulation/….) of colour data and or of transparent formatting
of an image.
Texture
position in the 2D graph. Often
represented in normalised value to make it independent of the resolution of the texture. The Co-ordinate texture is associated to
a vertex and therefore represents the projection of the para metrication of the texture on the 3D
model. It is to be noted that one
same vertex can have many texture co-ordinates.
Group of co-ordinates X, Y
and Z that represent a precise point in a 3D space. Synonym of "point".
Plural
of vertex.
Effect
produced by a too small opening that limits the light exiting a system of
projection or entering a system of acquisition. This limiting opening can be found anywhere in the
system. The effect of the vignette
makes the intensity on the side of the pattern projected or on the side of the
image acquired is weaker. Obviously
if we see the vignette on an image of projected pattern the effect can come from
the projection or the acquisition.