Creating a Voxel Model Variant

Overview

A static voxel-model asset-generation test case (asset_kind = "voxel-model") sculpts one 3D model out of opaque #rrggbb voxels into a [voxel] volume, toward a goal described in a brief. Its version offers one or more variants, and a run selects exactly one. Every variant seeds the version’s common specs plus its own additive specs. The chosen variant’s slug is recorded in the run record, so every result is attributed to a specific build.

This guide is the procedure for adding a variant to an existing static voxel-model version. The authoritative rules live in Voxel cases and the Manifests overview.

For a rigged case (asset_kind = "voxel-animation") see Creating a Voxel Animation Variant.

Variant scope

An asset-generation case has no target model and declares no [[reference]]; resolution rejects any reference, common or per-variant. The model is human-reviewed against the brief, so a variant has no target to repoint.

A variant varies two things:

• the brief the model sculpts toward, through an additive spec: a tighter palette, a stricter operation budget, a required technique such as symmetry via the mirror op or a hard voxel-count cap, or another observable stylistic constraint;
• the bounding volume, by declaring its own [voxel] table. A variant’s [voxel] replaces the case’s for runs of that variant, so one case can offer the same subject at several sizes. A variant with no [voxel] inherits the case’s volume. The effective volume flows to the seeded tool config, the scored model, and any {{voxel}} value a spec template reads.

The asset_kind is version-level, so a variant cannot turn a static model into an animation. A genuinely different subject is a new case or a new version rather than a variant.

An asset-generation case declares no reviewer checklist. The model is judged as a whole against the brief it was seeded with, on the case’s single overall domain (see Judged on one overall rating). The variant brief is therefore the only place its constraint is recorded, so write it precisely enough that a reviewer can weigh it.

Procedure

1. Choose the variation

Decide the constraint the variant imposes and keep it consistent everywhere:

• slug, lowercase, used in test-case.toml and the spec filename, such as symmetric;
• display name, title case, the variant’s name, such as Mirror-Symmetric;
• description, one line naming the constraint.

Favor a single constraint a reviewer can observe in the regenerated model, either rotating in the 3D viewer or in the preview PNG.

2. Write the variant brief

Create specs/<slug>.md, stated as a delta against the common brief:

• open by stating which common brief it builds on, by name;
• state the added or tightened constraint in precise, testable terms: exact colors, an operation cap, the technique required;
• reaffirm that it sculpts toward the same brief, with only the added constraint changing.

A spec whose source ends in .hbs is rendered per run and may read {{voxel.width}}, {{voxel.height}}, and {{voxel.depth}}, so a brief that states its volume reads correctly at every size variant.

A variant spec may reference the common specs freely, since they are always seeded, and must never reference another variant’s spec.

3. Create the variant file and list it

Write variants/<slug>.toml as a standalone TOML document whose top-level keys are the variant’s fields, then add its path to the variants array in test-case.toml. The first entry is the default. Paths inside resolve against the version folder, and dest defaults to source.

variants/symmetric.toml

slug = "symmetric"
name = "Mirror-Symmetric"
description = "Same subject and volume, built left/right symmetric using the mirror op."
spec = [{ source = "specs/symmetric.md" }]

# variants/double.toml: the same subject in a doubled volume
slug = "double"
name = "Double Size"

[voxel]
width  = 100
height = 40
depth  = 152
background = "transparent"

# test-case.toml: add the new file to the ordered list (first = default)
variants = ["variants/base.toml", "variants/symmetric.toml"]

What resolution enforces, and what a variant leaves alone:

• spec entries are additive on the common specs. Within one variant, no two seeded specs may share a dest.
• A reference entry is rejected for this test type, on the case and on a variant.
• A variant’s [voxel] is validated exactly as the case’s: width, height, and depth greater than zero, and a valid background.
• asset_kind is version-level, so a variant declares none.
• A variant declares no review items, matching the case.

Update the human-readable comment in the manifest that enumerates the variants so the list stays accurate.

Validate your work

From the repository root, lint the specs:

npm run lint:specs   # markdownlint-cli2 + cspell over test-cases/**

If cspell flags a legitimate domain term, add it to .cspell/project-words.txt rather than rewording good prose to dodge the dictionary.

Seed and render the new variant, and re-check the existing ones to confirm your edits changed nothing for them:

tcab seed   --test-case <slug> --version <version> --variant <new-variant>
tcab prompt --test-case <slug> --version <version> --variant <new-variant>

Read the seeded output to confirm the new variant’s brief is self-contained and that its effective volume is the one you intended.

The backend’s definition store is immutable per case version, so force a re-ingest before running:

scripts/reingest.sh --force <slug>

Force re-ingest overwrites the stored version in place and is for development only. Adding a variant edits an existing version, so do it only while that version is unpublished; a version a published run references is frozen and needs a new version instead. Then exercise the variant with Run a Test Case.