[Bf-interface] Units presets problems

[Ton Roosendaal]

Hi,

I guess it has been used wrong since the introduction of imperial unit mapping then.
With this patch it shows its full weakness.

I don't think we have to argue about who's right or wrong, I just explain the meaning and design concept behind the Blender unit and the scale factor. Other meanings and design concepts can be used as well.

A proper procedure to handle that well:

- a serious design attempt to really make a better way of handling units
- support from the previous designer (or module owners), to make sure you don't overlook things.

I firmly believe in the value of following design concepts and be very strict in it. This will keep things simple and consistent. Of course, any design will always have certain limits, but patching these limits with conflicting ideas in mind then only creates problems. 

-Ton-

--------------------------------------------------------
Ton Roosendaal  -  ton at blender.org   -   www.blender.org
Chairman Blender Foundation, Director Blender Institute
Entrepotdok 57A, 1018 AD, Amsterdam, the Netherlands

> On 10 Nov 2016, at 21:40, Bastien Montagne <montagne29 at wanadoo.fr> wrote:
> 
> Fwiw, this scene scale setting has been used as 'unit factor' for years 
> (think I’ve always known it used that way since I learned Blender code, 
> at least). So commit https://developer.blender.org/rB7f3da8f does not 
> change anything here, it only makes it slightly easier to use 
> (especially for Imperial units with their complex conversion values from 
> Metrics). But the fact of setting scene scale factor to the conversion 
> value from meter (since we assume 1m == 1BU) to whatever 'basis' unit 
> user want to use is quite old thing.
> 
> Not saying this is especially good thing, always found it rather 
> confusing, think this is an old hack to get quick unit system working - 
> but it’s hooked rather deeply in UI, transform and some operators code 
> at least…
> 
> Bastien
> 
> Le 10/11/2016 à 19:56, Ton Roosendaal a écrit :
>> Hi,
>> 
>> This should really be handled. Check mail below.
>> 
>> My suggestion is to rewind the commit.
>> 
>> Units code was not meant to work this way and only gets more confusing. Mapping the blender unit (the internal value of "1") to kilometers, millimeters, inches or lightyears should just work, without doing anything strange in the UI as happens now. It's a mapping. Not a scale factor.
>> 
>> The scale factor that gets used now was meant to scale the grid floor and to define defaults for adding new objects. That was meant for cases you want still work with meters as unit, but have grid floor draw in smaller or bigger units.
>> 
>> Fixing or improving unit handling is welcome, but then please do it either really good, or don't touch it.
>> 
>> -Ton-
>> 
>> --------------------------------------------------------
>> Ton Roosendaal  -  ton at blender.org   -   www.blender.org
>> Chairman Blender Foundation, Director Blender Institute
>> Entrepotdok 57A, 1018 AD, Amsterdam, the Netherlands
>> 
>>> Begin forwarded message:
>>> 
>>> From: Sergey Sharybin <sergey.vfx at gmail.com>
>>> Subject: [Bf-committers] Units presets problems
>>> Date: 8 November 2016 at 09:59:44 GMT+1
>>> To: Blender Developers <bf-committers at blender.org>
>>> Reply-To: bf-blender developers <bf-committers at blender.org>
>>> 
>>> Hi,
>>> 
>>> There was a hot discussion just before 2.78 release about unit presets
>>> commit [1].
>>> 
>>> This change exploits scene scale with something it was never intended to
>>> do, causing following issues:
>>> 
>>> - Using millimeters preset causes newly added objects to be much bigger
>>> than the camera far culling, which causes visual artifacts and overall
>>> inconvenience.
>>> 
>>> - Scene scale is used for various things, for example numeric input,
>>> causing issues like [2]
>>> 
>>> This is getting quite problematic and counterproductive are for artists,
>>> but yet it's not really my area. So i would like to see our UI team to
>>> handle this.
>>> 
>>> [1] https://developer.blender.org/rB7f3da8f
>>> [2] https://developer.blender.org/T49960
>>> 
>>> -- 
>>> With best regards, Sergey Sharybin
>>> _______________________________________________
>>> Bf-committers mailing list
>>> Bf-committers at blender.org
>>> https://lists.blender.org/mailman/listinfo/bf-committers
>> _______________________________________________
>> Bf-interface mailing list
>> Bf-interface at blender.org
>> https://lists.blender.org/mailman/listinfo/bf-interface
>> 
> 
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