# Threejs Screen Space Ambient Occlusion

> Implement a production GTAO path in Three.js. Use for half-resolution horizon sampling, reversed-depth reconstruction, bent-normal encoding, full-resolution bilateral reconstruction, environment-light application, contact grounding, and halo diagnosis.

- Skill: `gabrielmoreira/threejs-screen-space-ambient-occlusion` (Agent Skill, multi-file: 3 files)
- Install (CLI): `npx skillmds@latest add gabrielmoreira/threejs-screen-space-ambient-occlusion`
- Raw SKILL.md: https://api.skillmd.com/api/skills/gabrielmoreira/threejs-screen-space-ambient-occlusion/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- Author: gabrielmoreira (https://skillmd.com/u/gabrielmoreira)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/gabrielmoreira/threejs-screen-space-ambient-occlusion

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# Screen-Space Ambient Occlusion

AO estimates missing ambient visibility. It must modulate indirect lighting, not repaint all scene color with a dark multiply.

## Workflow

1. Verify linear depth and view-space normals.
2. Reconstruct view position consistently.
3. Sample horizon visibility in a controlled radius.
4. Estimate AO and optional bent normal.
5. Denoise with depth/normal-aware filters.
6. Apply to indirect diffuse and environment response.

Read [references/gtao-bent-normal-pipeline.md](references/gtao-bent-normal-pipeline.md).

## Failure conditions

- direct light and emission are darkened;
- radius is specified only in pixels;
- foreground silhouettes cast thick screen-space halos;
- depth discontinuities are blurred together;
- AO remains strong at distances where its world radius is subpixel;
- bent normals are treated as ordinary geometric normals;
- the implementation claims temporal accumulation even though this path has none.

## Routing boundary

This skill owns GTAO gathering, bent normals, denoising, and AO application.
Use `$threejs-image-pipeline` only when its depth/normal buffers or pass order
must be coordinated with other image-space systems.