V-Ray 6.2 does not have Bump to Glossiness Map

[^Lele^]

Some observations.

• The Max bitmap and the VRay on the old Isotropic seem to blur more with distance (which causes some of what the Bump to Glossiness Map is supposed to solve, but also reduces distant crawlies in animation).
• Blur offset (like the Max docs say) blurs in 2d texture space (like pre-blurring in PS).
• Sharp Isotropic in VRayBitmap does not have much softening in the distance, which may be worse for animations, but is likely better for stills.
• To my eye Elliptical looks like the best balance, but it will require adjusting your shaders because the change is so different that the look could be altered. Best to set this when you create the VRayBitmap node so all tweaking is based on your chosen filtering method. Summed Area on Max Bitmap also looks nice.
• The different filtering methods require manual tweaking of the blur and blur offset amounts, and likely of other portions of the shader (esp glossiness).
• I hadn't realized just how different Max Bitmap is from VRayBitmap.
• YMMV

Let me complement your findings with what i know of the two bitmap loaders.

a) Blur :
This is slightly misnomered, in that what it really does is step through the mip levels.
At its default of 1.0 it uses whatever it deems right for that view, the higher the distance, the lower the mip.
At 0.01 it will use the highest-resolution mip for all calculations which will be sharp, but much slower, and possibly more memory intensive.
It will surely be sharp, but it will very likely devastate convergence rates, meaning *much* more AA will be needed to have the bitmap properly sampled (much more so for temporal coherence!), as the mip-mapping for that texture has effectively been disabled.
Further, if using a vrayBitmap to load a tiled texture at the right mip level on demand, using the highest resolution could also have enormous RAM usage impacts (f.e. one loads a 32k px square terrain texture whole, instead of the right mip resolutions depending on distance.).
Going above 1.0 conversely lowers the resolution of the mip map used.
Which of course results in more or less blur, hence the parameter name.
You may be better able to see this with some custom mip-tester image, rather than a procedural.
This is the same for our bitmap loader, with the catches outlined below:

b) VrayBitmap Filtering Methods:
Isotropic can be assumed to work about the same as the Max default filter.
Sharp Isotropic simply chooses a higher resolution mip than plain Isotropic, resulting in sharper-looking details. (Most of the time. The selection heuristics are complex.)
It's essentially the same as lowering blur, but crucially this filtering mode does it just enough, without overtaxing the sampler or the user's RAM.
Elliptical filtering is going to be sharp at high glancing angles, but quite soft at facing ones, compared to the isotropic filtering.
It's best used for stuff that's near parallel to the view and goes far in the distance, like walls, roads, water planes, and so on.

c) Memory:
Summed Area for the max loaders is pretty, but very memory intensive. use with care.
The very best memory usage and overall sharpness can be had with .tx textures and the sharp isotropic filtering mode.
At most, blur could be lowered a tiny bit (how much depends on how many mip levels there are. go very slow and check.), but *never* should it be set at 0.01 lest nightmares happen.

Here's a test.
Notice the Blur parameter maps 1:1 with the vrayBitmap "Filter Amt.", and you only need to use one of either.





On what the bump2glossiness does:
It aims to solve the issue with bump maps filtering at a distance.
The further away one goes from a bumped surface, the less detail the map is able to provide, and the resulting surface glossiness gets higher with distance as a result.
The bump2glossiness computes an exact glossiness map and drives the shader appearance with that, instead of the hard-to-filter bump when the viewing distance increases, preserving the shader's look regardless.

the docs' exact quote:

VRayBump2Glossiness utility texture generates a reflection glossiness texture from a bump or a normal map.
Use of this texture avoids the effect of overly shiny or too highlighted glossy parts of objects seen at a distance.
With a reflection glossiness texture generated from bump/normal map, proper reflection glossiness is achieved at any distance, while detail is preserved.