Display a ground circle around the player
 

I don't know if an existing Add-on has that ability (search returned nothing)
I am not even sure the game's API provides the needed feature set, and doing it by other means could be against the ToS.

The need would be to display a circle on the ground (like any AoE effect) centered around the player.

Mandatory features would be :
- ability to select the radius of the circle (to match the range of important PBAoE skills)

Nice to have features would be :
- ability to configure circle color and brightness
- ability to configure multiple circles
- ability to activate circle based on conditions (in combat, duration after event, etc..)
- ability to configure other shapes than circle, and to offset them (ex: rectangle in front of you)

Curious to get your thoughts about this.

but the game already shows colored aoe areas - you mean that's not enough ?
You can even adjust the color for that in the gamesettings.

I think he means "like" the AOE circles but just around the player.

Why do you need such a circle? Makes no sense imo as it does not tell you anything game related and would just be a circle. You want to keep a distance to someone? There are addons which show the distance to group members afaik.

And about your question:
Not possible via game's API or at least not that easy, and definately not in dungeons!

One could try to paint a texture on the ground but this be a huge texture which wouldn't show properly all the time as one would need to recalcaulate the size etc. always during each movement. Some of these calculations wouldn't be even possible (or not that I'd know about).
And this would definately be a mess to calculate, keep it updated and trying to manage no serious FPS drops at the same time.

I would imagine the intended purpose would be for use as a rangerfinder, so you know exactly what the radius of an ability with "X" radius was going to hit.

But yeah, unfortunately, I don't want to say its completely impossible but it would be some 17th dimensional black geometry to do it if at all.

well, it should be possible. download Lib3D, but not the latest version. i guess it’s v34 with an example for a self created inner light. i‘m pretty sure you can do something similar with your stuff. i have no idea how this is, performance wise, but i guess it’s not the best one ;-)

Yes, exactly.

With some PBAoE (over time but without range visualisation like blade cloak, or instant like werewolf's fear), one meter can be the difference between hitting one target or hitting 3 targets with perfect positioning.

But if there's no way to reuse the builtin engine mechanics for drawing it, i wouldn't expect it to be realistically achievable with good results.

I see this is old but wondering if you ever figured this out. I'd love this on my tank to show a 12m circle around me for aoe pull from void bash 2 pc. I use sanctuary on one of my healers and it actually has this effect for its set animation to show players in your range and I use it to help guage where to drop some of my heals that drop around me in a radius.

As described above this is not possible and Lib3D neither would be able to draw a circle around you afai understood.

At least I do not know any way that Lib3d would be able to draw a circle without using a control. If there is any "circle" effect with a definable size i'm not aware of it.
If it's a control and would be able to draw it around you it needs to update that often (every few milliseconds) to keep the circle correct and move with you, that you'd have some performance issues...

it would be partly possible.
With partly meaning here, the result will probably be not usefull.

You can "draw a circle" on the ground using a normal control.
You then need to adjust the position according to your camera settings so the circle is centered arround the character.

You then need to adjust eccentricity if the circle according to camera settings and camera direction.
This just requieres some medium level math.

The difficult task will be terrain.
What I have described so far would only work if the ground is flat and perfectly aligned with one of the planes of the game's coordinate system. (I think it needs to be the x-z plane but i am not 100% sure out of the top of my head).

If the ground is not parallel to that plane, but with a constant angle in your location, you could implement an algorithm which determines this angle by walking around back and forth, left and right.

Now to why all this wont be really usefull:
* this wont work in any location with constantly changing slopes like cyrodil
* this will give a confusing graphic indication for the range of there are any obsicles or slope changes (like stars)
* it will draw the circle above stuff in the game (including the other character models), making it quite difficult for you brain to interprete distances and stuff.

So in conclusion, from my experience with working with such things in eso so far, you can get a decent estimate of what you want. But how good you can determine (as your brain is just an image interpreting software) if a player is within a certain distance will highly depend on your surroundings.