Ok, but this question was made by more users in other sites/threads? why blender have problems editing dense mesh? is a problem of CPU or GPU? have solution? the solution is easy/hard to implement?
It’s not an easy problem to solve, there will more optimizations in 2.80, and more after. Going into the technical details here is not particularly useful though, it requires being familiar with the Blender code. There is some information here:
https://developer.blender.org/T57936
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Personally I dont need preselection highlighting in the 3d view, as blenders selection works pretty predictable (which is in contrast not really the case in maya so there its really helpfull).
One area where its very handy though is uv mapping. As the correlation between the actual 3d geometry and the corresponding uvs is not communicated at all. So you end up selecting some uv elements just because you dont know how it all connects toghether.
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Dear friends. I’m Modo user and I’ve noticed that during low poly modeling in Blender 2.8 I miss preselection highlight. I`m fresh Blender user but I model things in Modo everyday.
Preselection highlight is needed for me mostly for vertex and edges to know is my pointer is point demanded edge/vertex or not.
I’ve noticed that without highlight I clicked few times on edges/vertex and I`ve missed them. Then I realised that highlighting is helping me with that.
I would like to have same feature in Blender but with no cost for performance that`s why I think it may be done as separate option in preferences (or as addon by someone).
I hope this helps. Even without that Blender is awesome 
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I can not wait to have this type of function coupled with a serious snapping.
I imagine the possibility during the positioning of a point, to have the interactive preview of all the snap points available near the area where I have to do the snapping.
It is a function that I have always wanted.
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I noticed that the built-in addon “snap_utilities_line” by @mano-wii already does the work described in this thread, what prevents a global adoption ??
@fclem
I noticed that as well.
I tried the “Make Line” tool out and made a mesh with 1 mil+ polygons to see how performance would be. There was a long 7 second pause when activating the tool or entering edit mode with the tool already active, but after that the highlighting worked fine with no discernible lag.
Fast preselection highlighting was not practical in 2.7 with old opengl, but should be possible in 2.8 with small performance cost. it will take some extra gpu ram. This is how it could work…
Edit mode drawing would have a selection ID buffer as an additional output target during all rendering. This would be smaller than the full 3d view, but it would take vram. It could potentially store more than one ID per pixel, but that gets more expensive in vram and render speed.
When moving the mouse, the full 3d viewport would NOT be re-rendered, as this would be slow. Instead the highlight would be rendered as a 2d overlay, and temporarily composited on top, like the overlay gismos, so it could be quickly changed every frame by just rendering that single primitive and re-compositing the overlay.
The cost of this method is… slightly more vram usage for the selection id buffer to always be used, a potentially larger overlay composite buffer (i don’t know if the current overlay buffer is as large as the viewport or just as big as the gismo area). A bit slower drawing always (but probably only a tiny bit), because fillrate is spent on the selection id buffer, and because of a few extra shader instructions to write an additional output target.
I suspect someone will eventually do this… they just have alot on their plate in 2.8.
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This would be a most welcome addition to Blender. 
Particularly when working with face dot selection in x-ray mode when two dots (one on the front of the mesh, one on the back) are close to each other.
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I really hope pre-selection highlighting comes to Blender soon.It is in all the other major DCC packages and makes for much faster and easier selecting.
Blender is moving at such a pace now so this would be a good time to include such a function.
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hoping this feature becomes a thing, I miss it from other programs like Modo. Makes precise selection a lot easier and like someone mentioned having it as an overlay option would allow people to turn it off if they dont like it 
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This is an anti-feature in Blender, so unlikely to happen.
https://wiki.blender.org/wiki/Reference/AntiFeatures
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People over at right click select have mentioned that anti-feature page but also pointed out that is very old at this point and the performance cost for preselect highlighting in newer versions of opengl being very low. Is consider it pretty arrogant of whomever had the final say to dismiss such a commonly requested feature without a good reason, they could always have an option for disabling it for the (presumably few since almost all dcc software has it) people who don’t want it.
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You’re making lots of assumptions here, you should read why it’s an anti-feature because it didn’t meniton anything to do with performance and the reasons are said to be from Blender’s Chairman(Ton) not the Devs.
Do you know how many commonly requested features Blender gets over time? tons of them.
Selection of faces/edges/vertices/bones/etc in Blender is not “click and guess” but IMHO one of the best working features of Blender - in which we beat other programs still. In 3d views you just don’t have singular selection possible (small elements, overlapping elements, etc). For that reason Blender has a heuristics that includes the distance to mouse, and cycles based on this distance (including on Z depth). If this doesn’t work well, I would call that a bug to solve - and have developers make it more predictable on single/2nd clicks…
So it’s hard to satisfy everyone, just because some other DCCs have it doesn’t mean anything in the context of Blender, and that’s the issue here. You’re expecting Blender to be like Maya or Modo which will never happen.
If they really don’t want it that’s up to them but I don’t agree with that reasoning. Having more precision and clarity without any performance cost seems like a clear win to me.
Blender might have good selection (I don’t know, seems about the same as every other program I’ve used) but why should that be a reason for not making it better?
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The issue is that Blender itself is inconsistent. It already has preselection in a number of tools, so the inherent need for it in some situations has been officially recognized. Whether or not it’s possible, or even a good idea is moot at this point- there needs to be an option (off by default) for preselect highlights in edit mode simply for the sake of consistency. Arguing against it is just delaying the inevitable, it’s the old “right click to select” argument all over again, and we all know how that one turned out eventually.
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I’m only conveying the information here.
I could care less if this is added or not.
If anyone needs convincing is but Ton, since his opinion bares more heavy weight than the rest of us.
You have to take it with the boss and ask him, why He’s so against it.
Right, but you’re conveying a position that is extremely dated and has already started to fold inward on itself. And no offense, but if you don’t have a horse in the race then I’m not really sure what you’re contributing to the discussion, as Ton certainly doesn’t need a proxy battle fought in his name (his opinions on the matter are well known and documented, as they were with left vs right click to select).
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It’s not dated if it’s still relevant, you might think otherwise but this pre-selection is different from Left VS Right in the context that it has more to do with design than practicality.
All that I have stated was this is an anti-feature since no one has brought that point in this conversation, and I didn’t see any link or even reference to it not even the proposal on RCS, so it was worth mentioning it.
Now you like or not, that’s a different story but my contribution is that this shouldn’t be just a blant copy from other softwares ,as not only the edit mode and object types would be affected but pretty much other areas of Blender that needs to be carefuly looked at.
That quote is wrong now and it was probably wrong back in 2012 too. The click selection accuracy in Blender is inadequate, and the hitbox size has a hard-coded pixel value so it can’t even be adjusted by the user (e.g. perhaps in Preferences > Input) to a preferred accuracy size.
I do have to guess what’s going to be selected. To illustrate, if I click where the 3D cursor is located Blender selects that vertex that is very far away instead of one of the two vertices below it that are closer to the click location (selected is ~50 pixels away from the click location [it’s also slightly further away in z-depth], but the two vertices below it are only ~40 pixels away). Why is Blender selecting a vertex that is further away than other nearby candidates?
In the absence of user-configurable click accuracy, preselection would at least allow for knowing just where this inaccurate selection was going to occur.
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