Hi Beat,
Thank you for the replies below:
This may be a misunderstanding of what function 31 does. Using the example:
CALL[], 66, 65, 25, 31
If the current ppem size is less than 25, fn 31 takes the cvt [pixel-] value that comes with cvt 65 and copies it into the slot for cvt 66, else it leaves it alone. The idea behind this is to tie slightly different cvt values to the same value if at sufficiently small ppem sizes the differences cannot (or should not) be rendered given the coarseness of the pixels. For instance, we may want the UC round strokes (O) to have the same width as the UC straight strokes (H), simply because at, say, 18 ppem the extra 20% stroke width of the round strokes cannot be expressed in terms of pixels.
Notice also that the settings of the cvt cut-in value will affect the outcome. If the actual distance of a feature is within the current cut-in value of the cvt value, then the cvt value will be taken, else the cvt has no effect (i.e. the actual or natural distance will be used). This is to prevent the worst accidents. Consequently, for small ppem sizes it is recommended to set the cvt cut-in to a higher value, such as 4 pixels, to ensure the effectiveness of the cvt. At larger ppem sizes, the cvt cut-in can be set to a smaller value, or even 0 (zero).
Philip may want to look into using the new control program, which folds the above functionality into the cvt and generates the pre-program automatically (see http://www.microsoft.com/typography/tools/42rnotes.htm, along with the updated template files that come with VTT 4.2). The control program also provides a simple way to set the cvt cut-in values, and proposes defaults for the cvt cut-in values and the ppem ranges to which they are to apply.
Hope this helps
Beat
My follow-up questions:
(1)
'If the current ppem size is less than 25'
What do you mean by current in this context?
Currently displayed?
Cuurently in the Pre-Program?
(2)
'Notice also that the settings of the cvt cut-in value will affect the outcome. If the actual distance of a feature is within the current cut-in value of the cvt value, then the cvt value will be taken, else the cvt has no effect (i.e. the actual or natural distance will be used). This is to prevent the worst accidents. Consequently, for small ppem sizes it is recommended to set the cvt cut-in to a higher value, such as 4 pixels, to ensure the effectiveness of the cvt. At larger ppem sizes, the cvt cut-in can be set to a smaller value, or even 0 (zero).'
I do not really understand this.
Please feel free to use simplistic answers - I am a type designer - but not a programmer!
(3)
'Philip may want to look into using the new control program, which folds the above functionality into the cvt and generates the pre-program automatically (see http://www.microsoft.com/typography/tools/42rnotes.htm, along with the updated template files that come with VTT 4.2). The control program also provides a simple way to set the cvt cut-in values, and proposes defaults for the cvt cut-in values and the ppem ranges to which they are to apply.'
I do have the above document, in fact I have documents on VTT printed-out that are about 4 cms thick! Beat, I am doing my very best to understand VTT, but I am struggling at times.
(4)
I also have VTT Version 4.2, so do I have the updated Template Files already?
(5)
Are you saying that there is never any need to manually edit the 'Pre-Program'?
(6)
If I edit the 'Control program' and compile, is a new 'Pre-Program' generated?
(7)
Maybe you might give me a step-by-step, 'hands held' explanation of how to do the following example please?:
How do I change the breakpoints where 1 pixel becomes 2 pixels (both Horizontal and vertical) at 10 ppem? Then the same, but for say 25 ppem? And again for 25ppem, but for only the horizontal? And again for 25ppem, but for only the vertical?
Sorry for my lack of grasp of this aspect of VTT.
Thank you
Philip Kelly
