Non-overlapping transparency for several objects

I would like to recreate a certain effect where multiple transparent objects won't create lesser transparent areas where they are overlapping each other. The following image illustrates what I would like to avoid:



Minecraft is a great example to show you what I would like to achieve:



The fountain has no overlapping water and it's not possible to artificially create those artifacts from the image above in Minecraft. A friend of mine told me that this effect might be possible by using the stencil buffer which in Unity is a Pro only feature. I'm curious if he's right with that. Minecraft (Vanilla) doesn't use shaders, so can you use the stencil buffer with the fixed function pipeline?

 

The following article deals with the same problem: https://en.wikibooks.org/wiki/OpenGL_Programming/Transparency

Is it possible to recreate this in Unity? Do you have other ideas on how to achieve this? How does Minecraft do it?

 

I even wrote a Tweet to Notch himself, now. Yes, I am desperate.

Is there a way to combine the results of two framebuffers? Like combining the results of two cameras? That way I could render everything except the water first and then render the water only (but non-transparent, i.e. opaque). After that I would combine both images where the water "framebuffer" will be treated as semi-transparent...

 

It's actually covered in the docs. And Stencil buffer is no longer exclusively a pro feature.
http://docs.unity3d.com/Manual/SL-CullAndDepth.html

But if this doesn't solve it for you, you probably want to render to an intermediate buffer without transparency, then composite it into the scene with.

Render textures.

 

@hippocoder: Thank you very much! It helped a lot!

I really didn't see this section in the manual before. Apart from that I also had to adjust the shader:

Code (CSharp):

1. Shader "Custom/Water"
2. {
3.     Properties
4.     {
5.         _Color ("Main Color", Color) = (1,1,1,1)
6.         _MainTex ("Base (RGB) Trans (A)", 2D) = "white" {}
7.     }
8.  
9.     SubShader
10.     {
11.         Tags
12.         {
13.             // I HAD TO REMOVE THE LINE "Queue"="Transparent"
14.             "IgnoreProjector" = "True"
15.             "RenderType"      = "Opaque" // and change the rendertype to "Opaque"
16.         }
17.  
18.         LOD 200
19.  
20.         // extra pass that renders to depth buffer only
21.         Pass
22.         {
23.             ZWrite On
24.             ColorMask 0
25.         }
26.  
27.         UsePass "Transparent/Diffuse/FORWARD"
28.     }
29.     FallBack "Diffuse"
30. }
31.  

Do you know why it only works with my changes? Anyway thanks in heaps for helping me!

 

Because transparent queue sorts differently otherwise polygons will clip each other so they have to be sorted back to front instead.

But if this works fine for your situation then it will work fine on all devices - don't worry about it - if it's good, in this case, it's good!

Generally that means you probably don't have transparent things behind transparent things that you still needed to see, ie meshes that are combined like X shaped grass billboards.

 

I tried the "Transparent shader with depth writes" example code given on that page, but it doesn't work. I'm using 5.0.1.

 

Isn't there some functional code that will do this, since it's a fairly common problem that needs to be solved?

 

I got it to partially work using BrightBit's modified version that he posted farther above; but it only eliminates overlap for polys that are part of the same mesh. Multiple meshes will still have overlap. Is there any method to eliminate that?

 

hi. i found solution for this problem. iam using URP



Shader "Custom/Water"
{
Properties
{
_Color("Main Color", Color) = (1,1,1,1)
//_MainTex("Base (RGB) Trans (A)", 2D) = "white" {}
}

SubShader
{
Tags { "RenderType" = "Transparent" "Queue" = "Transparent" }
LOD 200

ZWrite Off
Blend SrcAlpha OneMinusSrcAlpha



Pass {
Blend SrcAlpha OneMinusSrcAlpha
Blend One OneMinusSrcAlpha
ZWrite Off
Cull Off
Stencil {
Ref 10
ReadMask 10
Comp NotEqual
Pass Replace
}
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#pragma target 3.5

#include "UnityCG.cginc"

struct appdata {
float4 vertex : POSITION;
float2 uv : TEXCOORD0;
};

struct v2f {
float2 uv : TEXCOORD0;
float4 vertex : SV_POSITION;
};

sampler2D _MainTex;
float4 _Color;

v2f vert(appdata v) {
v2f o;
o.vertex = UnityObjectToClipPos(v.vertex);
o.uv = v.uv;
return o;
}

fixed4 frag(v2f i) : SV_Target {
fixed4 col = tex2D(_MainTex, i.uv) * _Color;
col.a *= _Color.a;
col.rgb *= col.a; // Preserve color intensity when transparent
return col;
}
ENDCG

//UsePass "Transparent/Diffuse/FORWARD"
}
//FallBack "Diffuse"
}
}