chr.schmitz wrote:an anyone explain, why D, G, and A are treated differently?
If you look at those keys on a real keyboard, they are very slightly different, in that the widths of the insets for the surrounding sharps are slightly different on the left and right sides for Gs compared to As, whereas the insets are equal for a D.
chr.schmitz wrote:And, why First DA and First GA, as well as Last DG and Last A are also treated in a different way, respectively?
For the same reason, i.e. the widths of insets of the neighbouring sharps.
chr.schmitz wrote:I can see only four different key types in naturals:
A natural without any sharp to the left or to the right (e.g. last C in keyboard with 61 keys).
A natural with only a sharp to the left (E and B).
A natural with only a sharp to the right (C and F).
A natural with sharps to the left and to the right (D, G and A).
Furthermore, there are two special cases, which can be represented by one of the above listed keys:
First DA and First G are the same as CF.
Last DG and Last A are the same as EB.
Not quite!
chr.schmitz wrote:Although this scheme is extremely flexible, it does not seem to allow to create keyboards with keys, which are not parallel. When creating a photo realistic console, keys are never optically parallel. However, this seems to be possible, when editing the ODF directly, where each single key of a keyboard is represented individually.
Even having one up/down image per key can't perfectly handle images with perspective, since with perspective the appearance of each key also needs to depend on the states of its two neighbours, as well as its own state. I.e. for a truly photo-realistic perspective rendering you would actually need six images (and states) per key (in most cases). I think a few sample sets do go to those lengths, but it makes things very complicated in the organ definition, and others approximate a perspective rendering with just two states.
Perspective key renderings aren't possible in the CODM, since it's intentionally designed to be reasonably quick and simple to learn and use, whilst being flexible enough to create professional-quality organ definitions. St. Anne's doesn't have perspective key rendering (for example), but it does have a virtual console that gives a 'photo-realistic' impression overall, and works well aesthetically and functionally, I feel.