How to Make a 3D Game with Codex

Can OpenAI Codex make a game?

Yes. With access to a project and its development tools, Codex can implement controls, cameras, collision behavior, objectives, and menus. A 3D game also needs models that fit its setting. Codex + Thrixel brings asset generation into the same workflow, so the agent can request props and environment objects while working on gameplay.

Thrixel's Build World skill guides planning, engine setup, model preparation, and playtesting. A small game with a clear win condition is a useful first project: deliver three packages, finish a race, or find the key to an exit. The agent has an observable result to test before expanding the design. This prompt-led development process is also called vibe coding a game.

How do you connect a 3D model generator to Codex?

The Thrixel MCP server exposes tools for generating, inspecting, editing, and exporting models. MCP lets Codex call these tools from the project. Build World is the workflow the agent follows; the MCP connection supplies the asset operations it performs.

Start with Codex installed, access to the local game project, and a Thrixel account. Ask Codex to install Build World and follow the Codex setup instructions, including the Thrixel sign-in flow:

Install the build-world skill from https://github.com/thrixel/build-world and follow the setup instructions in that repo.

Confirm that both the skill and the Thrixel tools are available in the session. For manual MCP configuration, the official Codex MCP documentation describes server setup and connection checks. Connecting an asset tool alone does not connect a local Unity, Roblox, or Unreal editor; each engine has its own setup.

Can GPT-6 Astra build a 3D game?

GPT-6 Astra is a model available in Codex for complex work across code and tools. Codex provides the project environment and tool access; Astra is the model doing the reasoning. Thrixel generates the meshes and textures requested by the agent. The same division of work applies when another supported coding model is selected.

Select Astra in the available model controls, or use codex -m gpt-6-astra in Codex CLI. OpenAI's model guide documents selection and availability. A game brief should name the engine, target devices, desired assets, and completion condition regardless of the selected model.

How to make a game with Codex and Thrixel

1. Choose the engine and describe the game

After setup, ask Codex to use Build World. Include the player action, goal, art direction, and expected controls. For a browser game, a first prompt might be:

Use the Build World skill to make a Three.js delivery game on a colorful island. Generate a small truck with separate wheels, cottages, crates, and a lighthouse using Thrixel. Add keyboard and touch controls, three delivery stops, a timer, and a restart button. Test a complete delivery route and check the models from the gameplay camera.

2. Generate and prepare the 3D assets

Codex turns the brief into an asset list and calls Thrixel with text prompts or reference images. For the delivery game, the truck needs separate wheels while a cottage can be grouped as static geometry. Named parts give the agent specific targets for revisions, such as widening the truck cab or changing the lighthouse roof.

Before placing each asset, the agent checks its hierarchy, scale, orientation, and materials. Triangle reduction and grouping prepare it for the project's asset budget. Models remain in the Thrixel workspace, so browser edits can be retrieved for the game.

3. Test the game and revise it

Playtesting checks whether a delivery can be completed, the camera follows the truck, and the restart flow works. Build World's gauntlet loop turns inspection into further changes. Feedback such as “the truck clips through the dock when turning” gives Codex a concrete issue to investigate and retest.

Can Codex build Unity, Unreal, Roblox, and Three.js games?

• Three.js: JavaScript gameplay and GLB models for browser games. Build World can publish a finished web build to thrixel.world.
• Unity: C# scripts, scenes, and FBX models, with Unity Editor and CLI setup. Read how to build a Unity game with AI or open the Unity setup page.
• Roblox: Luau scripts synced through Rojo, uploaded model assets, and Studio playtests. The Roblox AI game guide explains the workflow, with setup on Thrixel for Roblox.
• Unreal Engine: FBX imports, Blueprint interactions, and editor control through Unreal MCP. Read the Unreal AI game guide and Unreal setup page.

Which AI 3D model generator works with Codex?

Thrixel supplies an MCP connection for model creation and editing. Other generators also offer agent integrations: Meshy documents Codex support, and Tripo demonstrates an Astra-driven Unreal workflow. Compare the revision workflow as well as the first generated result.

With Thrixel, a model's named parts can be edited, the assets persist in a shared browser workspace, and Build World guides their preparation and testing in the engine. This supports requests such as changing a vehicle body while keeping its wheels usable for animation. Meshy's MCP documentation notes that API-generated models do not automatically appear in its web workspace, a distinction worth considering when moving between agent work and browser editing.

Common questions about making games with Codex

Can Codex generate 3D models from an image?

Codex can pass a reference image to a connected generator such as Thrixel. The generator produces the model; Codex inspects it and handles its integration into the game. A reference should make the object's silhouette and required moving parts clear.

Can Codex improve an existing game?

Yes. An existing project can use Thrixel to replace placeholder props, add missing assets, or revise part-based models. Specify which scene or interaction should change and the behavior that should be checked afterward.

How do I publish a game made with Codex?

Finished Three.js and Unity WebGL builds can be published to thrixel.world through Build World after testing the exported game. Roblox experiences are published through Studio. Unreal projects follow their target platform's packaging and distribution workflow.

Is Thrixel included with a Codex subscription?

Thrixel asset generation uses separate generation credits. Model selection in Codex does not change the Thrixel account's asset budget. Current generation options are listed in Thrixel's plans.