Material preset "Metal" for extruded custom shapes

[Regina Henschel]

Hi Miklos,

Miklos Vajna schrieb am 02.02.2022 um 08:50:
> Hi Regina,
> 
> On Sun, Jan 30, 2022 at 11:20:33PM +0100, Regina Henschel <rb.henschel at t-online.de> wrote:
>> I want to make rendering similar to actual rendering in MSO in case we have
>> an import from MSO. MSO uses for the attribute c3DDiffuseAmt the special
>> value 43712/65536 in case of "Metal", otherwise 65536/65536.
>> Currently I use this special value in my ongoing work [4] to detect, that
>> the shape 'wants' a Metal-rendering like MSO. The attribute c3DDiffuseAmt
>> has the corresponding attribute draw:extrusion-diffusion in ODF. So a
>> document imported from MSO binary format and then saved to ODF looks still
>> as MSO-kind, when reopening the document. But it is somehow a misuse of that
>> ODF attribute.
>> Do you think, that I should stay with that approach? Alternative would be to
>> use a marker in an interoperability bag. But that would loose the
>> information when writing to ODF.
>>
>> Opinions?
> 
> It seems to me that both of these are useful -- could we have both? I.e.
> add a new "diffuse metal" (or any other suitable name) property for the
> MSO behavior and keep our "metal" for the existing LO way?

LO has only a 'metal' from my last commit, which I now think has errors. 
  It is clear, that MS Office renders it using the material color. 
Besides seeing it in examples, the material color is mentioned in VML 
and in "legacyMetal" in OOXML. And although the description in ODF is 
not really clear, it surely has no reference to the material color. So 
we have an ODF way of 'metal' and a MS Office way.

> 
> Then you could map the MSO c3DDiffuseAmt to the "diffuse metal", and
> have both types of metal in the same document. Yes, this means going
> through the usual new feature checklist[1], but if you have time to do
> that, probably that would be better than a misuse or a grab-bag.

It is more the question what we want, than how much time I have. The 
current state is already in Gerrit, so someone else could continue the 
work if necessary.

There will be a similar problem, when importing extruded shapes from 
OOXML. There the descriptions in section 20.1.10.50 in 
ISO_IEC_29500-1_2016 contain not only specular color based on material 
color, but ambient color based on material color too. And that can be 
expressed in ODF neither.

If no one strongly objects and if it will be OK that it lasts some time 
till finished, let's go with an additional attribute in ODF.

> 
> [1]
> https://wiki.documentfoundation.org/Development/Writer#Adding_a_new_feature
> has that list, but it's not specific to Writer, perhaps we should move
> that to some more common place.
>

So I would have to add handling of the new attribute in a lot of places. 
The question is, do you (or someone else) will have time to mentor me 
when needed?

Kind regards,
Regina