Image to Three.js Model
img2threejs/img2threejs
Rebuilds the object in a reference image as a procedural, animation-ready Three.js model written entirely in code, using staged sculpting with quality checks.
The .achx animation file format and its save/runtime split. An agent skill from vchelaru/FlatRedBall.
Install Achx Format
$ npx skills add vchelaru/FlatRedBall --skill achx-format -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install vchelaru/FlatRedBall achx-format --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/vchelaru/FlatRedBall.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.claude/skills/achx-format .claude/skills/achx-format && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "achx-format" agent skill from https://github.com/vchelaru/FlatRedBall/tree/NetStandard/.claude/skills/achx-format into .claude/skills/achx-format/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "achx-format", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/vchelaru/FlatRedBall/tree/NetStandard/.claude/skills/achx-formatType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add vchelaru/FlatRedBall --skill achx-format -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install vchelaru/FlatRedBall achx-format --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/vchelaru/FlatRedBall.git skills-src && mkdir -p .agents/skills && cp -r skills-src/.claude/skills/achx-format .agents/skills/achx-format && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "achx-format" agent skill from https://github.com/vchelaru/FlatRedBall/tree/NetStandard/.claude/skills/achx-format into .agents/skills/achx-format/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "achx-format", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add vchelaru/FlatRedBall --skill achx-format -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install vchelaru/FlatRedBall achx-format --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/vchelaru/FlatRedBall.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/.claude/skills/achx-format .cursor/skills/achx-format && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "achx-format" agent skill from https://github.com/vchelaru/FlatRedBall/tree/NetStandard/.claude/skills/achx-format into .cursor/skills/achx-format/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "achx-format", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/vchelaru/FlatRedBall.git --path .claude/skills/achx-format--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add vchelaru/FlatRedBall --skill achx-format -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install vchelaru/FlatRedBall achx-format --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/vchelaru/FlatRedBall.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/.claude/skills/achx-format .gemini/skills/achx-format && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "achx-format" agent skill from https://github.com/vchelaru/FlatRedBall/tree/NetStandard/.claude/skills/achx-format into .gemini/skills/achx-format/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "achx-format", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install vchelaru/FlatRedBall achx-formatInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add vchelaru/FlatRedBall --skill achx-format -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/vchelaru/FlatRedBall.git skills-src && mkdir -p .github/skills && cp -r skills-src/.claude/skills/achx-format .github/skills/achx-format && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "achx-format" agent skill from https://github.com/vchelaru/FlatRedBall/tree/NetStandard/.claude/skills/achx-format into .github/skills/achx-format/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "achx-format", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add vchelaru/FlatRedBall --skill achx-format -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install vchelaru/FlatRedBall achx-format --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/vchelaru/FlatRedBall.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/.claude/skills/achx-format .opencode/skills/achx-format && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "achx-format" agent skill from https://github.com/vchelaru/FlatRedBall/tree/NetStandard/.claude/skills/achx-format into .opencode/skills/achx-format/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "achx-format", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
achx-format- GitHub stars
- 578
- Token cost
- ~975 tokens
- SKILL.md length
- 347 words
- Files
- 1
- Skills in repo
- 32
- Repo updated
- First seen
- Licence
- MIT
At a glance
The .achx animation file format and its save/runtime split. An agent skill from vchelaru/FlatRedBall.
- Game Development work in your project
- SKILL.md covers The save ↔ runtime split (the…, Landmines, Per-frame color (signpost) and Key files
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
What it does
Achx Format is an agent skill from vchelaru/FlatRedBall. The .achx animation file format and its save/runtime split. Triggers: .achx, AnimationChainListSave, AnimationChainSave, AnimationFrameSave, ToAnimationChainList, FromXElement.
Its SKILL.md is about 980 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.
It sits in Game Development. The repository describes itself as: Cross-platform 2D game engine focused on ultimate productivity built in .NET. The licence is MIT.
When your agent uses it
- Game Development work in your project
Example prompts
- “/achx-format”
What it can do on your machine
Read from SKILL.md and the folder at commit fa654ab. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md.
From the folder's file list and the shell code blocks in SKILL.md.
Network
Links to these hosts (documentation or services it may open):
docs.flatredball.com
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Achx Format loads about 975 tokens when it runs. Until then it costs about 47 tokens; SKILL.md has 347 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from vchelaru/FlatRedBall at commit fa654ab, republished under its MIT licence (© vchelaru). 347 words, ~975 tokens.
Download SKILL.mdSave it as
.claude/skills/achx-format/SKILL.md (or your agent's skills folder).- name
- achx-format
- description
- The .achx animation file format and its save/runtime split. Triggers: .achx, AnimationChainListSave, AnimationChainSave, AnimationFrameSave, ToAnimationChainList, FromXElement.
.achx Animation File Format
.achx is the XML serialization of an AnimationChainListSave. It describes texture-flip animations: a list of chains, each a list of frames, each frame naming a texture + UV/pixel coordinates + timing (and, more recently, optional per-frame color). See the AnimationChainList file docs and the runtime API.
The save ↔ runtime split (the core thing to internalize)
There are two parallel class trees — a serialized "Save" tree and a runtime tree — and you convert between them. Don't confuse the two.
Save (.achx, Content/AnimationChain/) | Runtime (Graphics/Animation/) |
|---|---|
AnimationChainListSave ([XmlType("AnimationChainArraySave")]) | AnimationChainList |
AnimationChainSave ([XmlRoot("AnimationChain")]) | AnimationChain |
AnimationFrameSave | AnimationFrame |
- Load:
AnimationChainListSave.FromFile(fileName)→ToAnimationChainList(...)→ per chainToAnimationChain(...)→ per frameAnimationFrameSave.ToAnimationFrame(...). - Save: the
AnimationFrameSave(AnimationFrame template)ctor copies runtime → save. - Apply to a Sprite: runtime frames are pushed onto a
SpriteinSprite.UpdateToAnimationFrame(called fromUpdateToCurrentAnimationFrame/AnimateSelf). That method is the single hook where per-frame texture/coords/flip/color land on the Sprite.
Landmines
- Two deserialization paths, kept in sync by hand. Desktop uses reflection-based
FileManager.XmlDeserialize<AnimationChainListSave>. Android/iOS use a hand-written manual path (AnimationChainListSave.DeserializeManually/LoadFromElement, andAnimationFrameSave.FromXElement— aswitchon element local-name). Any new serialized element must be added to BOTH, or it loads on desktop and silently vanishes on mobile. ShouldSerializeXxx()controls XML output. Save-class fields useShouldSerializeXxx()methods so defaults/nulls are omitted from the.achx. New optional fields follow this pattern to stay backward-compatible (old files just lack the element).- Coordinate + time units differ from runtime.
AnimationChainListSave.CoordinateTypeis UV or Pixel —ToAnimationFrameconverts Pixel→UV by dividing by texture width/height.TimeMeasurementUnit(seconds vs. milliseconds) makesToAnimationChaindivideFrameLengthby 1000. The runtime is always UV + seconds.
Per-frame color (signpost)
Frames carry optional nullable tint: Red/Green/Blue/Alpha and a color operation. The .achx/Save side stores 0–255 ints and an editor-flavored op enum; the runtime side stores 0–1 floats and FlatRedBall.Graphics.ColorOperation, with mapping done in AnimationFrameSave.ToAnimationFrame. Applied to the Sprite in Sprite.UpdateToAnimationFrame (ApplyAnimationFrameColor). Read the source there for the exact channels, identity-on-null rules, and op mapping.
Key files
File (Engines/FlatRedBallXNA/FlatRedBall/) | Purpose |
|---|---|
Content/AnimationChain/AnimationChainListSave.cs | .achx root; FromFile, ToAnimationChainList, manual load |
Content/AnimationChain/AnimationChainSave.cs | one chain; ToAnimationChain, FromXElement |
Content/AnimationChain/AnimationFrameSave.cs | one frame; ToAnimationFrame, FromXElement, color map |
Graphics/Animation/AnimationFrame.cs | runtime frame |
Sprite.cs | UpdateToAnimationFrame — where a frame is applied to a Sprite |
© vchelaru, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
Just SKILL.md in .claude/skills/achx-format of vchelaru/FlatRedBall.
Open the folder on GitHubat commit fa654ab
Compare with similar skills
Achx Format next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Achx Format this skillvchelaru/FlatRedBall | 578 | — | ~975 | Automated safety check: Pass | MIT | |
| Image to Three.js Modelimg2threejs/img2threejs | 18k | 1 repos | ~8.2k | Automated safety check: Pass | Apache-2.0 | |
| Web CloneJane-xiaoer/claude-skill-web-clone | 1k | 1 repos | ~2.7k | Automated safety check: Pass | MIT | |
| Threejs Game Directormajidmanzarpour/threejs-game-skills | 2.5k | — | ~2.2k | Automated safety check: Pass | MIT | |
| Game Asset Generatorhtdt/godogen | 7.1k | — | ~2.8k | Automated safety check: Pass | MIT | |
| Threejs Gameplay Systemsvalkor-ai/loom | 1.2k | 1 repos | ~1.4k | Automated safety check: Pass | Apache-2.0 |
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Questions about Achx Format
What does Achx Format do?
The .achx animation file format and its save/runtime split. An agent skill from vchelaru/FlatRedBall. Achx Format is an agent skill from vchelaru/FlatRedBall.achx animation file format and its save/runtime split.
When should I use Achx Format?
Achx Format fits situations like: game Development work in your project.
How do I install Achx Format in Claude Code?
Run `npx skills add vchelaru/FlatRedBall --skill achx-format -a claude-code`. Or copy the skill folder (.claude/skills/achx-format in vchelaru/FlatRedBall) into .claude/skills/achx-format in your project. Claude Code loads it when a task matches its description.
How do I install Achx Format in Codex?
Run `npx skills add vchelaru/FlatRedBall --skill achx-format -a codex`. Or copy the skill folder (.claude/skills/achx-format in vchelaru/FlatRedBall) into .agents/skills/achx-format in your project. Codex loads it when a task matches its description.
Can I use Achx Format in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add vchelaru/FlatRedBall --skill achx-format -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/achx-format, .gemini/skills/achx-format, .github/skills/achx-format and .opencode/skills/achx-format in your project.
What does Achx Format need to run?
SKILL.md names no scripts, command-line tools or credentials: Achx Format is instructions for the agent only.
Does Achx Format access the network?
SKILL.md names 1 domain. As links in the text: docs.flatredball.com. This is read from the text; nothing was executed.
Is Achx Format safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Achx Format use?
Achx Format is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Achx Format use?
About 975 tokens (SKILL.md is roughly 3.9k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.
What are the alternatives to Achx Format?
Skills that share tags, products or a category with Achx Format: Image to Three.js Model (img2threejs/img2threejs, 18k stars), Web Clone (Jane-xiaoer/claude-skill-web-clone, 1k stars), Threejs Game Director (majidmanzarpour/threejs-game-skills, 2.5k stars) and Game Asset Generator (htdt/godogen, 7.1k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Achx Format?
vchelaru (a GitHub user) maintains it in vchelaru/FlatRedBall, which has 578 GitHub stars. The repository holds 32 skills in this directory. The repository was last updated on October 8, 2026.
Source: vchelaru/FlatRedBall on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.