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revision 1.91 by tjl, Fri Nov 29 09:21:54 2002 UTC revision 1.92 by tjl, Fri Nov 29 09:49:26 2002 UTC
# Line 337  input corresponds to, in a perceptron-li Line 337  input corresponds to, in a perceptron-li
337  fashion\cite{widrow60adaptive,rosenblatt62neurodynamics}.  fashion\cite{widrow60adaptive,rosenblatt62neurodynamics}.
338    
339  From this picture, we can formulate the following points:  From this picture, we can formulate the following points:
340  To be distinguishable,  To be distinguishable, \label{secfeaturevec}
341  \begin{itemize}  \begin{itemize}
342  \item A feature vector for a given texture should be always the  \item A feature vector for a given texture should be always the
343      same, and not a smudged distribution;      same, and not a smudged distribution;
# Line 449  this would remove the use of the texture Line 449  this would remove the use of the texture
449    
450  In this section, we discuss our hardware-accelerated implementation  In this section, we discuss our hardware-accelerated implementation
451  of unique backgrounds .  of unique backgrounds .
452  Our main platforms are NV10, i.e. OpenGL 1.3 + GL\_NV\_register\_combiners,  Our main platforms are NV10, i.e. OpenGL 1.3 +
453  and NV25, i.e. NV10 + GL\_NV\_texture\_shader2.  \url{GL\_\hyp NV\_\hyp register\_\hyp combiners},
454    and NV25, i.e. NV10 + \url{GL\_\hyp NV\_\hyp texture\_\hyp shader2}.
455    
456  One important goal for the implementation is that it should be easily  One important goal for the implementation is that it should be easily
457  applicable in a variety of situations.  applicable in a variety of situations.
458  For example, mapping between paper and screen can be complicated,  For example, mapping between paper and screen can be complicated,
459  e.g.~fisheye.  e.g.~fisheye.
460  Because of this, we have  Because of this, we have
461  adapted the OpenGL model: the background ``texture coordinate'' is set  adapted the OpenGL model:
462  and then a vertex is rendered using glvertex. If a vertex program  the background ``texture coordinate'' is set
463  extension is available, it is used to allow the use of vertex and texture  and then a vertex is rendered using glvertex.
464    If a vertex program
465    extension is available,
466    it is used to allow the use of vertex and texture
467  coordinate arrays.  coordinate arrays.
468    To achieve this, all processing to obtain shapes on the paper
469    must be done after the texture accesses, i.e. we cannot use
470    procedural geometry.
471  % XXX  % XXX
472    
473  This enables the use of distortion inside the nodes.  
474    %Performance: zoomability, memory, speed
475    
476  \subsection{Resource usage}  \subsection{Resource usage}
477    
478  In hardware rendering, the use of resources is critical  In hardware rendering, the use of resources is critical.
479  The two relevant types of resources here are texture memory  The two relevant types of resources here are texture memory
480  and rendering time.  and rendering time.
481    
482  Performance: zoomability, memory, speed  We have two rendering modes which make different
483    tradeoffs between these goals: direct, where
484    the same small basis textures are used, which takes 2-3 passes
485    with all texture units enabled, and
486    pre-rendered, where the repeating unit of the texture
487    is pre-rendered into a larger texture of its own, where rendering
488    takes 1 pass with one texture unit.
489    To achieve a satisfactory image quality in zooming
490    with the latter approach,
491    a relatively large texture has to be used.
492    
493    
494  \subsection{Colors}  \subsection{Colors}
495    
# Line 479  Color is the most dominant visual attrib Line 497  Color is the most dominant visual attrib
497  Therefore, it is essential that the overall colors of the  Therefore, it is essential that the overall colors of the
498  backgrounds are maximally diverse with respect to color perception.  backgrounds are maximally diverse with respect to color perception.
499    
500    However, we come again to the entropy arguments
501    in Section~\ref{secfeaturevec}:
502    too many different colors in one background are perceived just
503    as a mix of many colors, making all such backgrounds look the same.
504    The backgrounds of random texels discussed earlier are an
505    extreme example of this.
506    
507  %In addition to choosing perceptually diverse colors,  %In addition to choosing perceptually diverse colors,
508  %there is the the question of how many colors to use.  %there is the the question of how many colors to use.
509  %  %
510  Using multiple different colors in a background allows  % Using multiple different colors in a background allows
511  a multitude of different combinations  % a multitude of different combinations
 but too many different colors in one background are perceived just  
 as a mix of many colors, making all such backgrounds look the same.  
 As an extreme case, consider the example of random texels discussed earlier.  
512    
513  To maintain color balance,  To maintain color balance,
514  we use a small palette of carefully chosen colors for each background,  we use a small palette
515  independent of the basis textures producing the shapes of the background.  of carefully chosen colors for each background,
516  Register combiners are used to combine the shape with the colors  
517  as explained in the following sections.  % independent of the basis textures producing
518    % the shapes of the background.
519    % Register combiners are used to combine the shape with the colors
520    % as explained in the following sections.
521    
522  %The most important constraint for the colors is readability:  %The most important constraint for the colors is readability:
523  %% XXX This is our CHOICE for a goal, not an absolute one.  %% XXX This is our CHOICE for a goal, not an absolute one.

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