i solved that modifier puzzle now... turned out i had to update the customdata pointers in the mesh and set the modifier to Constructive and SupportsMapping.
Had to look in the draw code for it and found a reference to mesh->mloopcol, thats the customdata pointer for the MLOOPCOL layer.

got vertexcolor reprojection operational BUT... in order to see it on the active modifier, you need to add e.g. an array mod with count 1 after it... There is surely some hack somewhere in either the modifier system or in the vertex paint mode preventing the remesh modifier outputting the reprojection data, but it is there.

In rBe2f23d91b989e05ff743260d18c85a17f78439a9#225315, @Metin Seven (MetinSeven) wrote:

Hi Martin,

There's a (paid but very affordable) Blender OpenVDB add-on called OpenVDB Remesh that has an option to reproject the vertices in the latest update.

ZBrush also projects vertex color onto a mesh when using the Project All function. I assume it analyzes the vertex color data of the existing mesh and transfers it to the nearest vertices of the remeshed mesh. The more vertex detail in both the source and the destination mesh, the better vertex color details will be kept.

Thanks.

In rBe2f23d91b989e05ff743260d18c85a17f78439a9#225305, @Metin Seven (MetinSeven) wrote:

Sorry, I forgot a very important wish: reprojection of vertex colors, so vertex paint is preserved after OpenVDB remeshing.

Thanks again!

In D4530#104032, @Campbell Barton (campbellbarton) wrote:

Before getting into code review or looking into details I'd like to see example uses cases for this modifier.

Otherwise we could:

• Postpone until nodal modifiers are supported.
• Make this an optional post-process for the decimate modifier.

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All BMesh operators _could_ be made into modifiers, however the modifier system isn't designed for constructive modelling (at least not with many fine grained operations).

Hi, another patch incoming :)

Hi, i have made a small patch in order to attach that new remesher option to the remesher modifier. Should apply to sculpt-mode-features branch from April 5th, 2019.

And the winner is : 33cbcd73448fb1cedc083c2b1fb9a27489d09432 from November 26, 2018 , question is how to fix that... hmm

Can confirm the jittering behavior. Last known good commit is e60c49ecf06815039137c98f86a7198d6ee81e14 from November 25, 2018. (that time i last merged 2.8 into temp-fracture-modifier-2.8, and it works in the branch)
So i am trying to git bisect now from there till HEAD to find the faulty commit... I keep you posted.