Dorico is considered the king of automation, and I can confirm that. Strangely, however, when creating a project, the user must manually set the rastral for correct score layout, as the one the program sets is impractical (staves overlapping excessively). I wonder: why hasn’t Dorico yet provided the ability to automate the rastral when creating a new project? The user could always choose not to rely on this automation or modify the rastral later. I hope Dorico adds this feature sooner rather than later.
Hi Janus, and thanks for your feedback. The problem is that you can’t know the ideal rastral size before seeing how the score actually displays. In practice, choosing one rastral value over another isn’t like choosing one font preference over another. That’s why I think it would be helpful if Dorico could automatically calculate it during project creation, and then let us change it.
The rastral size determines the size and position of everything in the layout.
So the problem is circular.
But it all depends on the number of instruments you want in the score, having empty staves hidden or not, maybe the kind of instrument and if sheet music for that players is right up on their nose, or further away, etc.
Maybe you could make some project templates, having your preferences, and start from there for new projects
And how would it know how many pages you want (and haven’t yet entered?) Or do you want that to update automatically? If you add instruments should it change everything to fit? Does it (or should it) change your paper size if your score doesn’t fit? Or, if it decides to put more (or fewer) systems on a page? What about readability for low vision users? There are too many variables! That would be like asking Word (or another DTP) to change the font size automatically to get a better layout! What you are asking for (I think) if for Dorico to read your mind or make a judgment call for you.
Sorry if that sounds snarky, not trying to be mean. 
You can set the rastral size in the hub as you start and also change your defaults if you find you need to change it often. If it’s a matter of final layout, there are a number of things that one can do to achieve the look one wants – among them; note spacing, system and frame breaks, and of course size. All of these would be fighting against the kind of automation you are seeming to suggest.
-- Jim
In fact, I explicitly emphasized that this type of automation should be implemented during the project creation phase, and not during the process (when you can add new musicians, and the program wouldn’t know it). If you set a specific instrumentation at the beginning, the program could already calculate an ideal rastral, just like Finale did, and if you don’t like it, you can just change it.
Okay, and given a specific number of musicians, couldn’t the program calculate an ideal rastral just like Finale did when creating a new project? I don’t find that so unreasonable.
After setting the number of musicians, Dorico shows me the score it created, and I’ll tweak the rastral until I find the ideal one. Well, the program could find it automatically, too.
This is what Project Templates are for. They allow you to specify everything about your layouts, both the Score and Parts, to suit your personal preferences.
Finale frequently changed the staff size according to the number of staves, but I’m not sure I would call it ‘ideal’. I invariably had to change it back from the setting that I wanted, which was already set in my document template.
I wouldn’t object if the size were automatically determined, as long as the user had the ability to override it. I seem to recall that Finale could vary the size from one page (or system) to the next. Perhaps Dorico has that capability and I haven’t needed it yet.
When you choose one of the project templates on the Create New page of the Hub, Dorico already updates the Rastral size drop-down to show you the size that will be used when the project is created. What else would you want it to do?
It sounds like you’re asking for a different setup flow. In Finale, the document setup wizard asked you for the instrumentation (and things like time sig and key sig), so when Finale created the page layout, it could pick a (roughly) appropriate staff size. In Dorico, the space size is chosen before you add any players/instruments.
If you’re creating a new document from the Hub, using an existing template, then the space size is baked into the template, along with the instrumentation.
This happens with predefined projects, and that’s fine. But what about a new, non-existent instrumentation? Instrumentation can be infinite, and each time we need to find an ideal value for correct layout. If an automatic process were applied when setting up a new project without starting from a predefined one, it would be very useful.
I know this well, but it would only work with predefined instrumentation; and when setting up a new instrumentation, what’s the ideal rastral value? We can only know this by manually trying different values over and over again, and it would be nice if the program could automatically calculate and suggest it.
I also know that Dorico sticks to the rastral value I enter, but that’s because the program forced me to choose it; I’d like it to choose that value automatically.
I think you’re going in circles. If you’re setting up a new instrumentation, then you/Dorico can’t pick the best rastral size until you’ve picked all the instruments. Once you’ve defined your instrumentation and rastral size, then you can save that as a template and reuse it.
Remember that the choice of rastral size will also depend on things like whether or not you want condensing, and whether or not your’re hiding empty staves.
What’s the specific workflow that you’re envisioning?
Just knowing the number of instruments does not determine the ideal rastral value.
There are many other considerations that will affect how the layout appears, not least the size of the page and the style of the music, multiple lines of lyrics, presence/absence of many leger lines, chord symbols, dynamics etc. etc.
What happens next shouldn’t matter to the program because, if and when necessary, the user can always choose to modify the rastral. Other popular notation software automatically calculated the ideal dimensions of musical elements (including staves), and the user could immediately begin noting the music. This isn’t currently possible with Dorico because it forces us to manually find the optimal rastral size. I hope this automatic feature will be added soon.
It is a fundamental difference if you - as a user - set up a layout exactly as you like it. You have total control over many, many settings and options. Dorico puts it together and displays it for you, respecting all your settings and options. It does not have a brain on its own. It just follows your instructions. Even if you instruct Dorico to squeeze more notes into a system, more systems onto a layout page, than what would be desirable. You do have the responsibility all to yourself.