[Bf-vfx] Re: Focal length constraints usability

[Sebastian König]

Hey!

Great to hear it is getting closer to be trunkified!
I just tried a test build from 3 days ago from graphicall and noticed a few things, related to workflow.
Having never really tested your branch or really knew what it is about I think it was a good test what a user would think if he first sees the constraint options. :)

So:
- Having the two values set to 0.000 first was a bit strange, because I didn't know what the values represent. If the values will stay in mm, then maybe it would be nice to have them at the default focal length at first. 24mm for example

- After I figured out what the min/max values are, I wanted to test how they work. I have set the min value to 18, and then tried 23 for max value. But because i didn't change the default setting of 24, I couldn't change it to anything smaller than that, which makes sense of course, but felt a bit weird. So I guess i would rather like the expanding way of dealing with that.
Because let's suppose I know the focal length is something in between 18 and 22. If i see the constraint setting I would think that that's the place where I can control the refinement. But if I don't touch the focal length setting in properties panel, I cannot set the max value to 22. So I think it would be nice if focal length in that case would just switch to 22, the max setting.
Or, if i know it's something in between 30 and 35, the focal length would switch to the 30, the min setting. 

- Right now I have to look in the toolshelf and the properties, to the left and right of the screen for dealing with this. I think it would be nice to have it all in one panel. So the camera data in properties could still have all the settings for focal length etc, but since trying to guess the right focal length and setting the constraints for it now becomes more of a tool itself, there could be a setting for estimated focal length in the solve panel. Below that you have the 2 min/max settings for upper/lower threshold. If you set the estimated focal length bigger or smaller then the min/max settings below, it could expand accordingly. Because the 3 settings are then very close together it becomes more obvious to the user how they relate and what happens.

- the question is then still what happens if the user changes the focal length value in the properties. But in that case I think it could just override the estimated focal length.

I agree with Sergey, it does get a bit crowded, and what I just suggested would probably only make it worse. But rearranging the buttons is maybe not that big of a problem. 

I hope that makes sense. Can also discuss with Sergey on irc, maybe I can make these walls of text more clear there. ;)

Cheers!!

Seb




On 27. August 2013 at 20:58:18, Joseph Mansfield (sftrabbit at gmail.com) wrote:

Hey everybody,

I'm getting my focal length constraints work ready to commit to trunk but I have a couple of things to ask about how the interface should work before doing so.
The current minimum and maximum fields take absolute values (in either mm or px). Would it be more useful to provide an interval (say ±5% or ±2mm)? If so, the next question is irrelevant. Perhaps both options should be available, if it would be useful.
I currently have it so that, only if the constraint is enabled, the focal length intrinsic in the properties shelf cannot be adjusted outside of this constraint. Sergey has pointed out that the constraint is a tool property and shouldn't restrict any other property. So here are the other options:
Expand the constraint whenever the focal length is changed to outside the range.
Allow the focal length to go outside the constraint, but give an error if a solve with refinement is attempted.
Don't have any restriction at all (if you attempt a refinement with the focal length outside the constraint, the given focal length doesn't really mean anything.
So, please let me know what you think. Thanks!

Joseph Mansfield
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