ValveResourceFormat 

Library to parse and write Valve KeyValue formats

Fully fledged library to work with Valve's Pak (VPK) archives

Parser, decompiler, and exporter for Valve's Source 2 resource file formats. Supports models, textures, materials, maps, particles, and more.

OpenGL-based rendering engine for Source 2 game assets. Supports models, maps, materials, particles, and animations with PBR lighting.