[Bf-committers] Creating modifications to geometry nodes to enable dynamically subdividing

[happysmash27]

I think I may have finally reached the point where, in order to finish my project, I will need to start contributing the necessary functionality to Blender in order to achieve everything I would like to achieve in it.

I would like to subdivide more on some parts of my model, less on others, and would like to use geometry nodes in order to implement this. This could be achieved by:

1. Allowing for the delete geometry node to dissolve geometry, rather than just deleting it entirely.
2. Outputting information that allows one to isolate the face and edge points of each subdivision level.

This would allow for the following technique to be used to allow one part of a mesh to be subdivided on one level, and another to be subdivided on another, assuming a vertex group named "Group" containing the section of geometry which should be kept as subdivided:

1. Select all vertices with (Group >= 1)&(<Face point> > 1):
https://devtalk.blender.org/uploads/default/original/3X/a/9/a9f0ea698321ec0d05f9d9100ec27b452f4af36c.jpeg
2. Dissolve vertices.
3. Select all vertices with (Group >= 1)&(Edge point > 1):
https://devtalk.blender.org/uploads/default/original/3X/9/3/9330746239da59ae4af392f00c35df8474127f4d.jpeg
4. Dissolve vertices:
https://devtalk.blender.org/uploads/default/original/3X/7/0/701128b81024fb92c9d02d8a2d0da68df980986b.jpeg

Resulting in a smooth transition between levels which does not leave one side larger (or, in the case of 0 subdivision levels, less smooth) than the other:
https://devtalk.blender.org/uploads/default/original/3X/6/b/6bf78f12b4c3d0a511d11c15327bfda46b2b87c4.jpeg

I suggest:

Modifying the delete geometry node to include a third dropdown with "Delete" and "Dissolve" options, which is consistent these options being present in the x delete menu, and with the options already present also mirroring those in the x delete menu.

Modifying the subdivision surface node to output attributes for the Edge Points, and Face Points (https://en.wikipedia.org/wiki/Catmull-Clark_subdivision) as an integer which reflects which subdivision level they belong to. This would enable selecting only the edge or face points from a certain level of subdivision.

I would like to contribute these changes to geometry nodes, if possible, in order to have this functionality as soon as possible and complete my project enough to be functional before June.

https://wiki.blender.org/wiki/Process/Contributing_Code suggests contacting developers before working on new features, so this is what I am attempting to do now.