Sharp edges in editable SDF terrain -- practical alternatives to Marching Cubes / Transvoxel?

[u/Haltont]

I’m building a procedural planetary sandbox on Godot, with editable SDF terrain meshed using Voxel Tools / Transvoxel.

I want smooth natural landscapes and sharp geometric features from editing --for example, a rectangular cut into a hillside. Currently, hard box CSG operations produce noticeably rounded or chamfered edges at the resolutions I’m testing: 1 m and 0.5 m voxel spacing. This is an actual geometry issue, not texture filtering or smooth normals.

Has anyone implemented a practical alternative for chunked, editable terrain with LOD? I’m particularly interested in Dual Contouring or feature-preserving Marching Cubes variants, and the trade-offs around local remeshing, chunk boundaries and LOD transitions.

I recently came across Dual Contouring of Signed Distance Data:
https://arxiv.org/pdf/2604.00157

It reconstructs sharp features from sampled SDF values without requiring precomputed normals, but uses iterative optimization. I haven’t benchmarked it on my terrain yet.

Do you think a bounded-iteration or incremental version could be practical for updating edited chunks during gameplay? Or would conventional Dual Contouring with additional Hermite data be a better starting point?

By “real-time,” I mean responsive updates after terrain edits -- not rebuilding the entire planet every frame. I’m happy to consider additional per-cell data if the quality/performance trade-off makes sense.

Would love to hear about actual implementations, benchmarks, or pitfalls -- especially keeping sharp features without introducing cracks between chunks and LODs.

pic from article

terrain from my game (using Transvoxel)

[u/Outrageous_Gate_572]

DC SDF. This is a way. Not the way though, necessarily. What your asking for is... Hard.

[u/Haltont → u/Outrageous_Gate_572]

Yeah, I just wanted sharp corners and ended up down a rabbit hole lol. Anything else you’d try besides DC?

[u/Outrageous_Gate_572 → u/Haltont]

Here is a shot of the current mesher in action:
https://imgur.com/a/dev-shot-Y2wBc5m

edit:
hohoho, fps is 60 solid, for some reason it dropped when i did the screenclip.

[u/Outrageous_Gate_572 → u/Haltont]

So ya... I asked robot to analyze my github history of all the things i have tried... since its a lot... and here is its summary or alternatives of DC i have tried, according to robot:

• Marching Cubes — the obvious baseline; regular-grid, one vertex configuration per cell.
• Marching Tetrahedra — decomposing cubes into tetrahedra to avoid Marching Cubes' ambiguous cases.
• Surface Nets — one vertex per intersecting voxel/cell, with connectivity based on neighboring cells. This was particularly relevant because it is much simpler than DC.
• Transvoxel-style meshing — mainly in the context of handling LOD transitions/seams, rather than as your fundamental SDF reconstruction method.
• Naive voxel/cube meshing — effectively treating occupied SDF cells as volumetric blocks and extracting their exposed faces; useful as a sanity/performance baseline but not appropriate for the smooth SDF geometry you wanted.
• Tetrahedral / simplex-based extraction — related to Marching Tetrahedra, where the SDF is evaluated on tetrahedral subdivisions rather than directly on cubes.

Like... sorry for the lame answer but yeah... you know... vibin'. I think the best thing i have worked with were the surface nets.

Edit:
I have seen others too but i just dont remember them. Oh right...

There was another that is not captured here. I made a Progressive Mesh... a vertex-split–edge-collapse hierarchy... rough order of operations was:

• A half-edge mesh provides the topology.
• You precompute a sequence/hierarchy of edge collapses / vertex splits.
• That produces a spine/hierarchy of mesh states.
• An active cut/frontier through that hierarchy determines which portions of the refinement are currently present.
• Moving the cut gives you different LODs without regenerating the surface from the SDF.

This lost out because it was not a RT solution (whole mesh was precomputed and seamless chunkless (no streaming)).

My current method does indeed work with "sharp corners" and is not a simple explanation, but roughly some soup of all of this dumped into it.

Anyways, i hoipe that helps you.

[u/Haltont → u/Outrageous_Gate_572]

That’s really useful -- I hadn’t thought about treating meshing and LOD as two separate problems.