Convexity is not a tool designed by Wall Worm. But it is important enough to Wall Worm to merit its own page here.

Made by Maple 3D, Convexity is a level design toolset that compliments the Wall Worm tools. There are a few minor areas of overlap (the VMF exporter, for example) but overall the two suites serve different purposes.

Convexity has a collection of design tools that make it easier to create complex, valid world geometry inside 3ds Max. It also allows you to set entities for your game inside Max. There are many things inside Wall Worm that are limited if you do not own Convexity. For example, although the Wall Worm VMF exporter lists brush and point entities as export options, you can only create those entities if you own Convexity!

If you only have a budget for one plugin this year and are developing games in 3ds Max, you should consider Convexity.