[MDAL-Developer] 3D Meshes

[Paul Harwood]

Thanks Vincent  ... some cil

1 There seems to be a general lack of drivers capable of writing any sort
>> of data - according to the flags and therefore also according to the C API
>> which checks the flags. UGRID, for instance, was mentioned but the Ugrid
>> driver capabilities do not include the ability to write ANY data. Is that
>> correct? It seems to contradict what has been said elsewhere.
>>
>
> UGRID does not write dataset for now, but it is on wish list...
>

Damn. I think I am going to have to make the PLY driver RW - to allow
testing since as format it can support everything.

There are three drivers that can write meshes (2DM, SELAFIN and UGRID). Of
>> these only one can write data - SELAFIN - and only on vertices. This is
>> very limited. Is it
>>
> The flags also say that DataOnFace can be written by the TUFLOW FV driver
>> but that meshes cannot, and that data can be written by the DAT drivers.
>> But none of that helps with creating a new mesh with data of any type (let
>> alone 3D).
>>
>
> Not sure TUFLOW FV can write anything.
>

You are right - I mean to say FLO2D - which has the DataOnFaces write
capability set

>
>> 3 The C API MDAL_G_addDataset() method explicitly excludes (i.e. there is
>> a validation check to enforce the exclusion) creation of DataOnVolume
>> datasets. This does make the conversation earlier in the email chain about
>> how to create these datasets incorrect. Is there a reason for this
>> exclusion and is there a way around it.
>>
>
>  Since there is a check about the supported data location just before this
> enforced exclusion, I don't see any reason, but maybe Peter can know about.
>

I think I might raise a PR taking this check out - since it should be up to
the DataOnVolumes flag to determine if a driver's createDataset() will work


>
>
>
>> Thanks for any pointers / comments
>>
>> Paul
>>
>> On Thu, 17 Jun 2021 at 10:22, Paul Harwood <runette at gmail.com> wrote:
>>
>>> Ok, thanks. Got it now
>>>
>>> On Thu, 17 Jun 2021 at 10:20, Peter Petrik <
>>> peter.petrik at lutraconsulting.co.uk> wrote:
>>>
>>>> base net is same as 2D mesh, verticals are just datasets defined in
>>>> https://github.com/lutraconsulting/MDAL/blob/42eb61f880f99ca0aa89a72f5afc5193b2f061e2/mdal/api/mdal.h#L648
>>>>
>>>>
>>>>
>>>> On Thu, Jun 17, 2021 at 11:07 AM Paul Harwood <runette at gmail.com>
>>>> wrote:
>>>>
>>>>> To be more precise - I can see how to add volume based datasets but
>>>>> not how to add the vertical structure - i.e. the number of volumes per face
>>>>> of the base net.
>>>>>
>>>>> On Thu, 17 Jun 2021 at 08:18, Paul Harwood <runette at gmail.com> wrote:
>>>>>
>>>>>> We probably need to change or clarify the README which says that 3D
>>>>>> data is not supported for UGRID. Does that column mean something else ?
>>>>>>
>>>>>> Is the support read-only? I cannot immediately see how to use the C
>>>>>> API to write a layered 3D mesh.
>>>>>>
>>>>>> On Thu, 17 Jun 2021 at 07:27, Peter Petrik <
>>>>>> peter.petrik at lutraconsulting.co.uk> wrote:
>>>>>>
>>>>>>>
>>>>>>> https://ugrid-conventions.github.io/ugrid-conventions/#3d-layered-mesh-topology
>>>>>>> is supported
>>>>>>>
>>>>>>> On Wed, Jun 16, 2021 at 8:38 PM Paul Harwood <runette at gmail.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Sorry - in that last email when I said "is UGRID unstructured 3d
>>>>>>>> MESH supported"? I meant "is UGRID LAYERED 3d mesh supported"!
>>>>>>>>
>>>>>>>> On Wed, 16 Jun 2021 at 19:35, Paul Harwood <runette at gmail.com>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Peter
>>>>>>>>>
>>>>>>>>> Can I just confirm. I look at the GH readme and it says that only
>>>>>>>>> XMDF supports 3d (i.e. I guess TUFLOW). There is an issue about UGRID that
>>>>>>>>> mentions a PR. Also the Readme says that XMDF support for 3D is read-only.
>>>>>>>>>
>>>>>>>>> Is UGRID Unstructured 3D mesh supported?
>>>>>>>>>
>>>>>>>>> Is any 3D RW?
>>>>>>>>>
>>>>>>>>> On Wed, 16 Jun 2021 at 14:59, Paul Harwood <runette at gmail.com>
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>> That makes sense. Thanks. I think that ugrid is what I want
>>>>>>>>>>
>>>>>>>>>> On Wed, 16 Jun 2021, 14:45 Peter Petrik, <
>>>>>>>>>> peter.petrik at lutraconsulting.co.uk> wrote:
>>>>>>>>>>
>>>>>>>>>>> I think we only support TUFLOW 3d data and UGRID specification
>>>>>>>>>>> for 3D stuff, which limits your options quite a bit :)
>>>>>>>>>>>
>>>>>>>>>>> P.
>>>>>>>>>>>
>>>>>>>>>>> On Wed, Jun 16, 2021 at 3:28 PM Paul Harwood <runette at gmail.com>
>>>>>>>>>>> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> Hi all
>>>>>>>>>>>>
>>>>>>>>>>>> I am thinking about voxel based 3D data in meshes.
>>>>>>>>>>>>
>>>>>>>>>>>> I am aware of this
>>>>>>>>>>>> https://github.com/qgis/QGIS-Enhancement-Proposals/issues/158
>>>>>>>>>>>>
>>>>>>>>>>>> The question I have is a simple one :
>>>>>>>>>>>>
>>>>>>>>>>>> Absent any other constraint, what would be the "best" format to
>>>>>>>>>>>> use to hold and transfer voxel based 3D mesh data?
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>>>>>>>>>>>>
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>
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