This is an modified version of VHLT v34 by ???? ???? (Uncle Mike) designed for the Xash3D engine (bsp v31). While this tool is compatible with Goldsource not all of the features can be used properly, but here are some notable ones available to you:
Compiling time reduced by 20% on 64-bit
HLCSG compiling speed greatly improved on all versions
Quality of lightmaps improved
Ability to modify lightmap quality
Ability for models to cast shadows
I still haven't figured out how to use this correctly as you can see in the Dust2 screenshot, but to modify the lightmap you need to use two parameters in conjunction with one another.
The first one is zhlt_texturestep which ranges from 2 to 64, default is 16. It defines the amount of texels per luxel. I like to think of this as 'one unit of the light map is equal to 16 units of the texture map' (I don't know if that's correct). The second one is zhlt_maxextent which ranges from 8 to 128, default is 16. This should be used in conjunction with zhlt_texturestep using a simple formula: (zhlt_texturestep * zhlt_maxextent) - zhlt_texturestep For example: (16*16)-16=240, where 240 is the subdivide step.
Use these parameters in any brush entity or in worldspawn (global map settings). This will greatly increase your Alloc_block so be careful.
Models can now cast static shadows (supports transparent models too). This can be enabled with the zhlt_studioshadow 1 parameter. You can change the quality of the shadow with zhlt_shadowmode (0/1/2), where 1 is the default. Higher values result in a higher quality, but 0 doesn't seem to be compatible with transparent models
The archive includes 64-bit versions of this as well which offer up to a 20% increase in compiling speed, use less memory, etc.