UV Flatten distorted plane

[nuki]

I am trying to generate nice, relaxed UVs for a distorted grid object. Ideally I would want to simply relax the initially generated UVs after distorting it but all the tools available seem to be focused on generating new UVs altogether. Having never done this kind of thing in Houdini I also struggle to understand how I could procedurally constraint eg. the outline of the grid to a square or all the points with @P.x==0 to a straight line.

UVs pre distortion

UVLayout post distortion

Quickly generated UVs in maya to outline what I'm after

river_UV.hip

Edited February 16, 2018 by nuki

[f1480187]

Smoothing geometry may help a bit. It will leave UVs straightened and tileable and reduce interpolation zigzags. It will also help UV Flatten to output proper geometry without such big distortion.

Also you may try Delta Mush, it may simulate results you need. Swap UV with P, then apply DM on straightened UVs using UV Flatten output as a second input:

delta_mush_uv.hipnc

[nuki]

thank you a lot, the delta mush method works great! Smoothing the mesh aggressively before flattening and then copy overthe uvs to the original seems to work fine as well.

[a41b]

I am reviving this thread because I am dealing with a similar problem, except that my model has several UV islands instead of one big island like the example above. The DeltaMush approach did not work for me beacuse of the UV islands. DeltaMush needs point attributes. When converting the UV attribute from vertices to points I lose the UV islands because of the connectivity of the points at the edges of the vertex islands.

What I want to achieve is the following:
1. create an initial UV layout with several uv islands (UV Flatten)
2. deform the geometry
3. relax the initial UVs to compensate for the distorted geometry from step 2

I am struggling to make the above DeltaMush approach work with UV islands. Any ideas?
Maybe someone has a completely different idea how to relax the UVs after the geometry deformation. My geometry is only deforming slightly. I am looking for a way to match the edge lengths/primitive areas of the UVs with the new (deformed) edge lengths/primitive areas of my mesh.

 

Edited July 8, 2019 by a41b

[a41b]

I have posted a RFE which is now implemented. Thanks SideFX

UV Relaxation of existing UV islands is now a feature of the UV Flatten node when "Preserve Seams" and "Preserve Layout" is turned on in Houdini 17.5.319.