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Multiple Valued Grid Format for Describing 3d Surfaces
Summary
Values of the depth at regular locations are stored as surfaces in
DDS supported formats. If the surfaces are multiple valued, multiple surfaces
are stored. Each surface has a matching mask. If the mask has value
zero, then the surface is not defined at that grid location.
The first surface is followed by the first mask in the dds structure.
And the n'th surface is followed by the n'th mask.
Programs
lndmrk2grid, landmark2surf, grid2lndmrk, grid2PtNorms, and PtNorms2grid
create or use this data structure.
grid Format Description
A regular grid consists of a regular array of nx by ny points.
Each point, (i,j), has a location (x,y) given by
x= x0 +(i-1)*dx
and
y= y0 +(j-1)*dy
where the value of
x0 is set by the dds constructs
in the dds dictionary.
Setting
axis= x y
origin.x=10
origin.y=20
delta.x=82
delta.y=96
specifies that the mapping between
(i,j) and (x,y) is
x=10+(i-1)*82
and
y=20+(j-1)*96.
Landmark data may have an offset and increment
associated with the line index and depth index.
In this case a mapping between the grid indices and the
landmark indices can be established using the
dds variables
axis=x y
step.x= 2
step.y= 3
base.x=10
base.y=200
This establishes the mapping
i = (di-base.x)/step.x
j = (li-base.y)/step.y
Names may be associated with each surface using the variables
name_1=name_of_the_first_surface
name_2= ...
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