Analysis of outlines/font errors

[ArchivePoster]

Posted by: Rabs
         

Hi all,

 

how to solve the problem of having 'systematically mis-oriented contours'

and 'Projection or freedom vectors at or near perpendicular'

This happens when i use  Tools/ Analyse Outlines  and

View/font errors

how can i resolve this problem?

how can one produce good outlines in the first place using a package like 'fontographer'?

any help much appreciated

regards

Rabs

[ArchivePoster]

Posted by: Si
         

From Beat...

 

Fontographer, I'm told, sometimes gets the contour orientation "wrong" (i.e. not in accordance with the TT specs, see http://www.microsoft.com/typography/tt/ttf_spec/ttch01.doc, "Outlines" "Figure 1-2"). Why it does that I don't know, maybe the cited part of the specs were inadvertently overlooked.

 

To fix this, choose "Display" "Options" then select "Outline Errors", the "interactive version" of "Analyze outlines". This will analyze the outlines of each glyph as it comes up (which may slow down your VTT "experience", hence be sure to turn it off when it's no longer needed). If errors are detected, a message will come up and ask permission to try to fix this. This works best on fonts that have not been hinted yet. If a glyph has been hinted already, VTT will find out whether it can preserve the hints. If it can't, it will ask permission to remove the hints for this specific glyph.

 

As to the projection vector being almost perpendicular to the freedom vector, this has to to with the "hinting technique". These vectors are concepts of the underlying TT engine. When hinting a control point, the control point typically has to give way to comply with the hint (or rather, the instruction). It does so along the freedom vector (FV). Compliance typically is achieved when a certain distance is reached. This distance is measured along the projection vector (PV). Now, if these two vectors are perpendicular (or, for the purpose of internal calculations, "nearly" perpendicular), the point can give way along the FV as far as it wants to, this will never amount to any change in distance along the PV (because they are perpendicular).

 

Typically, when hinting a font with VTT, this error never occurs, as VTT will take care of setting up these vectors properly. Quite typically, indeed, these vectors will be parallel, as set up e.g. by an XLink or a YLink. However, it may be that a font hinted with another tool, or when using the TT language directly (e.g. with an "ASM" statement in the VTT Talk window), these vectors get perpendicular, or nearly so. In the former case, consult with the vendor of the tool for a fix. In the latter case, re-think the use of the TT language.

 

Hope this helps.

 

Beat

[ArchivePoster]

Posted by: Rabs
         

Hi Beat,

 

thanks for your help!

just wandering if i've got the latest VTT zip file as i've tried to fix the contour orientation as you have said in your msge:

To fix this, choose "Display" "Options" then select "Outline Errors", the "interactive version" of "Analyze outlines".

 

but it doesn't work, i chose 'Display' then 'Outline Errors' - nothing happens

( there is no 'Options' menu within the 'Display' menu)

Also another query:

under the 'File' menu there is no 'Preferences' option  as stated in the VTT help file

any help much appreciated

Rabs

 

[ArchivePoster]

Posted by: Si
         

According to Beat's mail above errors will only pop up when you view a glyph with an error. Are you sure this sin't happening?

 

Si

 

 

[ArchivePoster]

Posted by: Rabs
         

hi Si

 

thanks for the advice

checked again and compiled the font and now all outlines are ok!:-)

regards Rabs

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