/[gzz]/manuscripts/AGPU/fonts.txt
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revision 1.8 by tjl, Sat Apr 12 11:33:46 2003 UTC revision 1.9 by tjl, Sat Apr 12 11:40:59 2003 UTC
# Line 1  Line 1 
1  ISSUES:  This proposal is a bit long - feel free to take just the parts
2  - how much should we discuss the texel-character stuff?  you're interested in.
 - what should we say about proportional fonts?  
3    
4  Legible text using the flexibility of modern GPUs  Legible text using the flexibility of modern GPUs
5  =================================================  =================================================
# Line 32  as movement starts, in a kind of a "moti Line 31  as movement starts, in a kind of a "moti
31  can be implemented optimally with a fragment program, and, with less  can be implemented optimally with a fragment program, and, with less
32  quality, with a combination of register combiners and LOD-biasing.  quality, with a combination of register combiners and LOD-biasing.
33    
34    The second approach is to change the filtering paradigm entirely.
35    This is possible because of the flexibility of e.g. the NV30.  We have
36    had some encouraging results from using NEAREST-filtering in OpenGL,
37    but where at each texel, the *texel distance* between the texel and the
38    font outline is stored. This allows the filtering to be based more on
39    the font outline and less the pixellated representation, approximating
40    a real font rasterer on the GPU.
41    
42  2. Subpixel rendering  2. Subpixel rendering
43  ---------------------  ---------------------
44    
# Line 43  rendered black-and-white text. Line 50  rendered black-and-white text.
50    
51  We show how a fragment program can be used to implement the sub-pixel  We show how a fragment program can be used to implement the sub-pixel
52  filtering by using the DDX, DDY and TXD instructions to access the  filtering by using the DDX, DDY and TXD instructions to access the
53  texture several times, for the ctriangular sampling filter commonly  texture several times, for the tri-triangular sampling filter commonly
54  used in subpixel rendering.  used in subpixel rendering.
55    
56  A lesser-quality approximation can be obtained on NV2X with three  A lesser-quality approximation can be obtained on NV2X with three
# Line 52  sub-pixel-shifted texture coordinates, w Line 59  sub-pixel-shifted texture coordinates, w
59  for discussing the inverting of the homogeneous coordinate transformations  for discussing the inverting of the homogeneous coordinate transformations
60  in the vertex programs to shift the texture coordinates in screen space.  in the vertex programs to shift the texture coordinates in screen space.
61    
 [ there are also some practical aspects related to rendering of mosaiced  
 fonts such as borders &c which we *can* discuss here if you feel like it  
 ]  
   
 3. Fragment-based text  
 ----------------------  
 The rendering of text strings from texture uses offset texturing: each  
 texel in the text texture stores the offset to the correct glyph in a  
 font texture. The rendering time depends only on the rendered size of  
 the text fragment and not on the number of individual characters.  
62    
63    Figures
64    -------
65    
66  FIGS!!!  FIGS!!!
67  - sharpening  - sharpening

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