/[gzz]/gzz/doc/pegboard/1010/PEG_1010.rst
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revision 1.1 by tjl, Sun Oct 6 16:31:21 2002 UTC revision 1.2 by benja, Sun Oct 6 16:44:05 2002 UTC
# Line 15  Main benefits Line 15  Main benefits
15    
16  - Allows buoys and nadir to work inside the C++ code for speed;  - Allows buoys and nadir to work inside the C++ code for speed;
17    while allowing the buoy to interpolate to a non-buoy.    while allowing the buoy to interpolate to a non-buoy.
18      
19    .. contents::
20    
21    
22  Concepts  Concepts
23  --------  --------
24    
25  Coordinate system type  Coordinate system type
26      E.g. "affine", "rotation", "fisheye", "buoytrans".      E.g. "affine", "rotation", "fisheye", "buoytrans".
27        
28            (Benja:) "buoytrans"?
29    
30  Derived coordinate system type  Derived coordinate system type
31      A coordinate system type whose possible transformations      A coordinate system type whose possible transformations
32      are a subset of another coordinate system type's transformations,      are a subset of another coordinate system type's transformations,
33      implemented internally by generating a set of parameters      implemented internally by generating a set of parameters
34      for the parent type.      for the parent type.
35        
36            (Benja:) Example? Is rotation derived from affine?
37    
38  Parent coordinate system  Parent coordinate system
39      A coordinate system through which the coordinates, having      A coordinate system through which the coordinates, having
40      been transformed by the child, are transformed::      been transformed by the child, are transformed::
41    
42          p_screen = parent(child(p))          p_screen = parent(child(p))
43            
44        (Benja says:) Where ``p`` is the original point (in child coordsys),
45        ``child()`` is the transformation of the coordsys itself,
46        ``parent()`` is the transformation of the coordsys' parent,
47        and ``p_screen`` is the final point in screen coordinates.
48        
49      All derived coordinate system types have exactly the same      All derived coordinate system types have exactly the same
50      parent coordinate system(s) and interpretations as the      parent coordinate system(s) and interpretations as the
51      parent coordinate system type.      parent coordinate system type.
52        
53            (Benja:) I don't understand this. Is 'parent coordinate
54            system type' the type of the parent coordsys or the
55            coordinate system type *this* coordinate system type
56            is derived from?
57            
58      Currently all coordinate systems have only one parent.      Currently all coordinate systems have only one parent.
59    
60      The theoretical point here is that the parent coordinate      The theoretical point here is that the parent coordinate
61      system's transformation at an uncountable set of locations      system's transformation at an uncountable set of locations
62      will affect the child coordinate system, unlike with      will affect the child coordinate system, unlike with
63      determining coordinate systems.      determining coordinate systems.
64        
65            (Benja:) I don't understand. Example, or something?
66    
67  Determining coordinate system  Determining coordinate system
68      A coordinate system which participates in defining another      A coordinate system which participates in defining another

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