Viewfinder

A shader debugging mod for Iris on Fabric that exposes an HTTP API and in-game commands for external tools and scripts to inspect, test, and automate shader development workflows.

Features

• Shader reload and error list - trigger shader reloads and capture compilation errors
• GPU timing metrics - collect per-pass GPU timing data (collects multiple frames to average out noise)
• Texture dumping - export textures as PNG or raw binary by name (colortex0, or custom texture)
• SSBO buffer dumping - dump shader storage buffer objects to disk for analysis
• Screenshot scheduling - schedule screenshots with configurable frame delay (for PT)
• Patched shader listing - find which patched shader errored programmatically by listing all and searching for "errored"

Installation

1. Install Fabric Loader (≥ 0.18.4) for Minecraft 26.1
2. Install Fabric API and Iris (which requires Sodium)
3. Drop the Viewfinder .jar into your mods/ folder

Usage

In-game commands

All commands are registered under /viewfinder:

Command	Description
/viewfinder status	Show current shaderpack name, error count, and API address
/viewfinder reload	Reload shaders and report any compilation errors
/viewfinder errors	List all captured shader errors
/viewfinder screenshot [frames]	Take a screenshot (optionally delayed by N frames)
/viewfinder screenshot result	Show the path of the last screenshot
/viewfinder metrics	Display per-pass GPU timings
/viewfinder ssbo list	List active SSBO buffers
/viewfinder ssbo dump <index>	Dump an SSBO buffer to ssbo_dumps/
/viewfinder texture list	List available colortex and custom textures
/viewfinder texture dump name <name> [raw]	Dump a texture by name (PNG or raw)
/viewfinder texture dump id <id> [raw]	Dump a texture by GL id (PNG or raw)
/viewfinder patched_shaders	List Iris patched shader files

HTTP API

Viewfinder starts an HTTP server on localhost:7150. A full OpenAPI 3.0 spec is available at GET /.

Method	Endpoint	Description
GET	/	OpenAPI 3.0 specification
GET	/status	Shaderpack status (loaded pack name)
POST	/reload	Reload shaders, returns success and errors
GET	/errors	List captured shader errors
POST	/screenshot?frames=N	Schedule a screenshot (default: next frame)
GET	/screenshot/result	Path to the last saved screenshot
GET	/metrics	GPU timing metrics
GET	/list-ssbo	List active SSBO buffers
POST	/ssbo?index=N	Dump SSBO at given index
GET	/list-textures	List available textures
POST	/texture?name=...&raw=bool	Dump texture by name
POST	/texture?id=...&raw=bool	Dump texture by GL id
GET	/patched_shaders	List patched shader files

All responses are JSON. Dumped files (textures, SSBOs, screenshots) are written to subdirectories inside the Minecraft game directory.