game-mesh-voxel-conversion

Game Mesh Voxel Conversion

Use this skill when the game should do an operation in one representation and

ship or render the result in another. Make conversion an explicit workflow with

resolution, error, and attribute rules.

Primary source: Geometry for Programmers by Oleksandr Kaleniuk

(https://www.manning.com/books/geometry-for-programmers), transformed and

paraphrased, especially chapters 10-12. Additional sources: "Marching Cubes"

by Lorensen and Cline (https://dl.acm.org/doi/10.1145/37402.37422), and

"Dual Contouring of Hermite Data" by Ju, Losasso, Schaefer, and Warren

(https://dl.acm.org/doi/10.1145/566654.566586).

Core Workflow

1. State the source representation and target representation.
2. State why conversion is needed: repair, render, collide, edit, Boolean,

offset, destruct, simplify, smooth, or export.

1. Choose the working grid or sampling resolution from visible error, gameplay

tolerance, memory, and streaming constraints.

1. Preserve or regenerate attributes deliberately: normals, UVs, materials,

skinning, collision layers, gameplay tags, and LOD metadata.

1. Pick the extraction algorithm based on shape needs: marching cubes/squares

for smooth organic fields, dual contouring for sharper features, or custom

contouring when curve output matters.

1. Validate geometry and gameplay behavior after conversion.

Conversion Patterns

Mesh To SDF To Mesh

Use when mesh operations are brittle but approximate output is acceptable:

• Fix holes, cracks, folds, or inverted triangles.
• Hollow or offset a model approximately.
• Merge or subtract complex shapes.
• Generate clean collision or render meshes from an implicit design step.

Expect loss of exact topology and possible loss of original UVs/materials.

Field To Mesh

Use marching cubes/squares when:

• The field is smooth and organic.
• Corners do not need to be preserved exactly.
• Linear interpolation on grid edges is good enough.

Use dual contouring when:

• Sharp features matter.
• Hermite data, gradients, or normals are available.
• One vertex per active cell is a useful output shape.

Voxel Operations

Use voxels or image masks when robustness matters more than exact surface detail:

• Dilation grows filled regions.
• Erosion removes boundary material.
• Erode then dilate to remove small noise.
• Dilate then erode to close thin cracks.
• Boolean union, intersection, and subtraction are simple on aligned grids.
• Connected-component labeling counts separate pieces.

Resolution And Error Rules

• Every grid conversion has an error budget. Name it before implementation.
• More resolution improves visual detail but increases memory and processing

cost quickly, especially in 3D.

• Anisotropic voxels or nonuniform world scale must be accounted for in

distance and neighbor rules.

• Store grid origin, cell size, axis order, and sign convention with the data.
• Use multiresolution or chunking when worlds are large.

Attribute Preservation Checklist

• Normals: recompute, transfer, or preserve?
• UVs: project, bake, discard, or regenerate?
• Materials: transfer by nearest surface, volume labels, or procedural rules?
• Gameplay tags: transfer by source primitive, volume region, or query?
• LODs: generate now or later?
• Collision: same mesh as rendering, simplified mesh, SDF, or voxel proxy?

Common Mistakes

• Converting only positions and discovering later that materials or gameplay

labels were the real asset.

• Using marching cubes for shapes whose main value is sharp edges.
• Treating a voxel grid as exact geometry instead of sampled occupancy.
• Running a mesh repair workflow with no before/after validity tests.
• Picking resolution from screenshots rather than gameplay tolerance and memory.