RTS range rings on map

Hello, I'm trying to make an effect like supreme commander where selection of a unit shows range rings that follow terrain height and overlapping ranges are not shown.

For example: https://i.ytimg.com/vi/8rPQzr11tcI/maxresdefault.jpg

I've been googling this for a few hours and haven't found a good solution - I don't think a projector is right because the rings become pixelated.

My game also has the strategic zoom so you can zoom out pretty far and the lines drawn should still be sharp.

Any help would be great!
Thanks.

 

I also went back to supreme commander to check out how it works - and the range rings follow the terrain exactly. It follows all the elevation changes in an area no matter how small they are, so it's not just putting a fixed number of lines in a circle.

 

I wanna to know too. Would be some masking shader technique I think.
The hidden floor effect started since 4:20 solved too if your case is solved.
I think they are similar technique?

 

I'm working on a shader and got this going:

It works fine for a cube that i've squished flat and tall. it follows whatever outline of any objects terrain, etc.
And I even got the circular version going with a cutout in the middle:

The middle is another cylendar that has a shader that just cuts it out of the previous object.

But its not perfect, the BACK of the cylendar remains transparent no matter what I'm doing so far. I changed the colors around and offset the inner cylendar for clarity:

If anyone knows a bit more about shaders please ping me!

 

The way it was done in Supreme Commander was 2d distance fields, one texture for each range, at a relatively low resolution. You render circles with a consistent falloff with a max blend mode. I'm not sure if they render the terrain again for each ring pass or as one "super shader".

For Planetary Annihilation we did something similar but we did it in screen space and projected rings onto the depth map as a full screen post process rather than rerendering the geometry. If you're using the deferred rendering path or real time directional shadows it should be possible to do.

 

I think it can achieve by using stencil buffer.

 

Yea, my stencil buffer was wrong. I didn't understand how the colorbuffer worked and that you can do the stencilOps without writing pixels.

Anyway once I understood it the solution came together quickly. Here's a couple range low poly range rings just for example:




What's nice is they follow the terrain perfectly. But its still not perfect, rotating the camera beyond certain degree's makes everything blow up:



I've tried changing the Queue tag but nothing seems to work. Any ideas why changing the camera direction changes everything?

I'm attaching the shaders below. To use this just have two shapes you want to draw on the ground - a larger outer one and a smaller inner one. For example:



Use this shader on the inner shape:

Code (CSharp):

1. Shader "Custom/NODRAW-stencil-minus-one" {
2.     Properties {
3.     }
4.     SubShader {
5.           Lighting Off
6.  
7.         //FRONT
8.         Pass {
9.             Tags {"Queue"="Transparent-100"}
10.             Stencil {
11.                 Ref 1
12.                 Comp always
13.                 Pass replace
14.             }
15.             Zwrite Off
16.             ColorMask 0
17.         }
18.  
19.         //BACK PIXELS ONLY
20.         Pass {
21.             Tags {"Queue"="Transparent-100"}
22.             Stencil {
23.                 Ref 1
24.                 Comp always
25.                 Pass incrWrap
26.             }
27.  
28.             Zwrite Off
29.             Cull Front
30.             ColorMask 0
31.         }
32.     }
33. }
34.  

And this shader on the outer shape:

Code (CSharp):

1. Shader "Custom/reveal backfaces" {
2.     Properties {
3.     }
4.  
5.     SubShader {
6.         Lighting Off
7.  
8.         //BACK PIXELS ONLY
9.         Pass {
10.             Tags {"Queue"="Transparent"}
11.             Stencil {
12.                 Ref 1
13.                 Comp always
14.                 Pass replace
15.             }
16.             Zwrite Off
17.             Cull Front
18.             ColorMask 0
19.         }
20.  
21.         //FRONT
22.         Pass {
23.             Tags {"Queue"="Transparent"}
24.             Stencil {
25.                 Ref 1
26.                 Comp notequal
27.                 Pass replace
28.             }
29.             Zwrite Off
30.             Color (1,1,0,1)
31.         }
32.     }
33. }
34.  

Again, any help on why this doesn't work at all camera angles would be great.