# Threejs Parallax Occlusion Mapping

Build silhouette-aware parallax occlusion mapping in Three.js WebGPU and TSL.

- Repository: https://github.com/scottstts/Threejs-Awesome-Graphics-Agent-Skills (956 stars)
- Category: Engineering
- License: MIT
- Last updated: 2026-10-22
- Runs scripts: yes, review before use

## Install

Claude Code: `npx skills add scottstts/Threejs-Awesome-Graphics-Agent-Skills --skill threejs-parallax-occlusion-mapping -g -a claude-code -y`
Codex: `npx skills add scottstts/Threejs-Awesome-Graphics-Agent-Skills --skill threejs-parallax-occlusion-mapping -g -a codex -y`
Cursor: `npx skills add scottstts/Threejs-Awesome-Graphics-Agent-Skills --skill threejs-parallax-occlusion-mapping -g -a cursor -y`
Gemini CLI: `npx skills add scottstts/Threejs-Awesome-Graphics-Agent-Skills --skill threejs-parallax-occlusion-mapping -g -a gemini-cli -y`

## Description

Build silhouette-aware parallax occlusion mapping in Three.js WebGPU and TSL. Use for height-field ray marching, relief UVs, clipped flat or curved silhouettes, inflated shells, self-shadowing, relief-aware shadow depth, and height-derived normals.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Parallax Occlusion Mapping

Treat relief as a coupled intersection, coverage, normal, and shadow system.
Do not stop at offsetting texture coordinates.

This skill contains exemplary examples and assets beyond descriptive guidance,
they're worth studying, referencing, or even copying. Use them sufficiently
when relevant and do NOT blindly skip them.

## Build order

```text
tangent frame and height convention
  -> view-ray march and hit refinement
  -> bounded or curved silhouette coverage
  -> shared marched sampling
  -> height-derived shading normal
  -> light-ray self-shadow march
  -> relief-aware cast/received shadow positions
```

Read [references/silhouette-relief-contract.md](references/silhouette-relief-contract.md)
for the intersection contract, flat and curved silhouette modes, shell
inflation, shadow integration, quality controls, and diagnostics.

Read the
[silhouette relief implementation](examples/silhouette-relief/ParallaxOcclusion.js)
for the complete TSL march, binary hit refinement, gradient-safe sampling,
coverage, horizon trimming, curved sag, and self-shadow function.

Read the
[complete bulkhead assembly](examples/silhouette-relief/silhouette-relief-system.js)
and its [packed procedural height maps](examples/silhouette-relief/bulkhead-height-maps.js)
for a wall, deck, relief columns, and overhead pipes using height-derived
normals, inflated cylinder shells, alpha-to-coverage, shadow-mask carving,
marched shadow depth, and received-shadow positions.

## Required controls

- world or UV relief scale;
- minimum and maximum view-march layers;
- silhouette bounds and feathering;
- curved-surface curvature or curvature callback;
- horizon trimming and edge erosion;
- self-shadow steps, bias, and strength;
- geometry, carved, and full-relief shadow modes;
- height, coverage, marched UV, normal, and shadow diagnostics.

## Failure conditions

The rest: https://github.com/scottstts/Threejs-Awesome-Graphics-Agent-Skills/blob/HEAD/skills/threejs-parallax-occlusion-mapping/SKILL.md