Wall Worm is a script and tool developer focused on 3ds Max and various Max-related pipelines. Historically, Wall Worm was devoted soley to optimizing the Source Engine asset pipeline. The Wall Worm toolset itself is a Source-only toolset. However, many new tools are generic in nature (for any game engine, VFX, VIZ, etc), such as the CorVex plugin and most other new tools.
See the official Autodesk blog feature about Wall Worm developer Shawn Olson, Wall Worm and Black Mesa: From Black Sheep to Black Mesa and Beyond.
Wall Worm tools allow you to create assets for Source in a way that was not possible before. You can build models, textures and levels inside one environment (3ds Max) and compile them straight into Source. Wall Worm tools have been used in the pipelines of many games including Dear Esther, Black Mesa and by designers of CS:GO Operation maps and many more.
Wall Worm works in collaboration with other 3ds Max/Source developers to help enhance all the tools available to designers and mod teams.
The bone tools allow you to give specific bones artbitrary surface properties, set mass bias and create hitboxes and hitbox groups.
Understanding Displacement Blend Texture Scale
This page explains one cause for displacement materials to be scaled incorrectly in Source as well as the solution. You should use bitmaps of equal dimensions in both materials controlling the Blend material.
Brush Geometry, 3D Skybox, 2D Sky, Animated Textures
Video tutorial and sample file on exporting a 3ds Max scene into a Source VMF file with Wall Worm.
A beginning to end example of making and exporting brush materials and decals.
A video and sample file to show you how to export textures, brush materials, decals and a simple level from 3ds Max into the Source Game Engine.
The Wall Worm Material Library Generator originally created DirectX Materials for all materials. But updates to the VMF Exporter changed the way materials are interpretted. Whenever possible, you should not use DirectX Materials.