Support reading SOG

[querielo]

PR adds read support for SOG. Previously, SOG could only be written via writeSog. This enables round‑trip conversion

input.ply -> output.sog -> restored.ply

or combining multiple .sog into one

input1.sog + input2.sog -> output.sog

What’s Included

• read-sog.ts: Reconstructs a DataTable
• zip-reader.ts: Minimal ZIP parser (STORE method + data descriptor) connected to .sog archives with no extra dependencies (no fflate).
• webp-decode.ts: WASM-backed WebP decoder (mirrors existing encoder approach) with no extra dependencies (no sharp).

Inverse Transforms

• logTransform (writer): sign(v) * ln(|v| + 1)
• Inverse (reader): inv = sign(v) * (exp(|v|) - 1)
• Opacity:
  • Writer stores sigmoid(opacity) → uint8
  • Reader applies logit(y) = ln(y / (1 - y))
• Quaternion:
  • Writer packs 3 scaled components + dominant index (alpha 252–255)
  • Reader restores missing component via unit-length constraint

Fixes #62

• I confirm I have read the contributing guidelines

[Copilot]

Pull Request Overview

This PR adds read support for SOG (Super-compressed Splat) format to enable round-trip conversion between PLY and SOG files. Previously, SOG could only be written but not read.

• Implements SOG reading functionality with inverse transforms for position, quaternion, and opacity
• Adds a minimal ZIP reader for parsing bundled .sog archives without external dependencies
• Includes a WASM-backed WebP decoder for texture decompression

Reviewed Changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
src/readers/read-sog.ts	Main SOG reader implementing inverse transforms and data reconstruction
src/serialize/zip-reader.ts	Minimal ZIP parser supporting STORE method and data descriptors
src/utils/webp-decode.ts	WebP decoder wrapper using WASM module
src/index.ts	Updated file reader to support .sog and meta.json input
lib/webp_decode.mjs	Compiled WASM module for WebP decoding
lib/webp_decode.c	C source for WebP decoder WASM module
lib/BUILD.md	Updated build instructions for both encoder and decoder
README.md	Updated documentation to reflect SOG read support

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[slimbuck]

Hey @querielo,

May I ask what your use-case is for combining multiple SOG into another SOG?

SOG is really a lossy compressed format and so decompressing->recompressing will result in overall quality loss.

[slimbuck]

Hey @querielo I pushed some updates directly to your branch, hope that's ok :)

Thanks so much for this PR!!

[querielo]

You are right.

Thank you!