Hello, could you please advice how to unwrap heightfield as shown on the attached image avoiding UV stretching on the slopes?
I feel like it should be possible to select faces with stretched UVs into a group somehow and then maybe UV Flatten them separately. If you could point me out to some best practices article for such cases it would be much appreciated. Thank you!

I believe the problem is that the geometry itself, being that an heightfield, is already stretched in those areas.

Have you watched the far cry 5 talk at gdc2018?
They (kind of) address this problem when talking about their “cliff tool”.

https://youtu.be/NfizT369g60?t=1245 [youtu.be]

This is pretty rough, but might work in your case.

Push a copy of the mesh so that @P = @uv. Measure the primitive areas of the original mesh and the uv mesh, compare, get the min/max, normalise, thats a rough guide of uv stretching.

Store that as an attribute, do what you want with it.

Andr
I believe the problem is that the geometry itself, being that an heightfield, is already stretched in those areas.

Thank you, And! The geometry isn't stretched but the uvs are. It was converted to vdb and then to polygons polyreduced.
The video link you provided is very useful, it gives me some other ideas for my project.

mestela
This is pretty rough, but might work in your case.

The trick you provided, mestela, looks pretty cool! I'll try to remember it.
It does give me the stretched uvs as I asked but the problem I've found with this solution is that
it gives me some stray small islands of stretched uvs and it's hard to filter them out using the threshold.

But it reminded me that there is a heightfield mask by feature that lets you select slopes by angle.
So I've ended up transferring the mask attribute to my new mesh and creating a group from that.

I still had to add plenty of vertical seams as the slopes were all the way around the mountain.
The result isn't perfect but it's a lot better than before and might be just fine.

Thank you, Guys!

illiastatkevych

Andr
I believe the problem is that the geometry itself, being that an heightfield, is already stretched in those areas.

Thank you, And! The geometry isn't stretched but the uvs are. It was converted to vdb and then to polygons polyreduced.
The video link you provided is very useful, it gives me some other ideas for my project.

mestela
This is pretty rough, but might work in your case.

The trick you provided, mestela, looks pretty cool! I'll try to remember it.
It does give me the stretched uvs as I asked but the problem I've found with this solution is that
it gives me some stray small islands of stretched uvs and it's hard to filter them out using the threshold.

But it reminded me that there is a heightfield mask by feature that lets you select slopes by angle.
So I've ended up transferring the mask attribute to my new mesh and creating a group from that.

I still had to add plenty of vertical seams as the slopes were all the way around the mountain.
The result isn't perfect but it's a lot better than before and might be just fine.

Thank you, Guys!

Can you provide the hip file or some tutorials ? Thank you!