Question Transparent Sorting & Stencils of a DrawMeshInstanced

I'm pretty happy with these hand trails but I've been stuck for days on trying to find a workaround for these transparent sorting issues.

From the research I've done it seems like it's basically unavoidable with a transparent shader but I figured I'd ask anyway.

There's probably a way to have the shader be opaque but still have the sorting of the instanced meshes with the newer ones on top. The problem then is that these instanced meshes cannot "fade out" as they scale up.

Any help is much appreciated.

Here's the shader:

Code (CSharp):

1.  
2.  
3. Shader "Trails" {
4. Properties {
5.     _MainTex ("Texture", 2D) = "white" {}
6.     _Color ("Color", Color) = (1,1,1,1)
7.     _CutOff("Cut Off", Float) = 0.5
8.     _Cull ("Cull", Int) = 2
9. }
10.     SubShader
11.     {
12.         Tags {  "RenderType"="Opaque" "RenderType" = "Transparent" }
13.  
14.         Pass
15.         {
16.             Stencil {
17.                 Ref 2
18.                 ReadMask 2
19.      
20.                 Comp NotEqual
21.                 Pass Replace
22.              
23.              
24.                     }
25.  
26.      
27.         Blend SrcAlpha OneMinusSrcAlpha
28.        
29.  
30.         ZWrite Off
31.        
32.      
33.  
34.          
35.  
36.             CGPROGRAM
37.             #pragma vertex vert
38.             #pragma fragment frag
39.             #pragma multi_compile_instancing assumeuniformscaling nolightprobe nolodfade nolightmap
40.             #pragma multi_compile _ TRAIL_ALPHACLIP
41.             #include "UnityCG.cginc"
42.  
43.             struct appdata
44.             {
45.                 float4 vertex : POSITION;
46.                 float2 uv     : TEXCOORD0;
47.                 UNITY_VERTEX_INPUT_INSTANCE_ID
48.             };
49.  
50.             struct v2f
51.             {
52.                 UNITY_VERTEX_INPUT_INSTANCE_ID
53.                 float4 pos    : SV_POSITION;
54.                 float2 uv     : TEXCOORD0;
55.                 UNITY_VERTEX_OUTPUT_STEREO
56.             };
57.  
58.               sampler2D _MainTex;
59.               float4 _MainTex_ST;
60.               fixed _CutOff;
61.  
62.      
63.  
64. UNITY_INSTANCING_BUFFER_START(Props)
65.     UNITY_DEFINE_INSTANCED_PROP(fixed4, _Colors)
66. #define _Colors_arr Props
67. UNITY_INSTANCING_BUFFER_END(Props)
68.  
69.             v2f vert (appdata v)
70.             {
71.                 v2f o;
72.                 UNITY_SETUP_INSTANCE_ID(v);
73.          
74.                 UNITY_INITIALIZE_OUTPUT(v2f, o);
75.                 UNITY_TRANSFER_INSTANCE_ID(v, o);
76.                 UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o);
77.          
78.              
79.                 o.pos = UnityObjectToClipPos(v.vertex);
80.                 o.uv = mul(unity_ObjectToWorld, v.vertex).xyz;
81.      
82.                 return o;
83.             }
84.  
85.    
86.  
87.  
88.             fixed4 frag(v2f i) : SV_Target
89.             {
90.                
91.                 UNITY_SETUP_INSTANCE_ID(i);
92.                 float2 multy = float2(4, 4);
93.                 fixed4 multy2 = UNITY_ACCESS_INSTANCED_PROP(_Colors_arr, _Colors);
94.                 fixed4 col = tex2D(_MainTex, i.uv * multy + _Time*.2f );
95.            
96.                   col *= multy2.w;
97.                 return col;
98.             }
99.             ENDCG
100.         }
101.  
102.     }
103. }

 

You are correct that there is no real solution to this. Not anything that can do exactly what you want performantly at least. Fast and correct sorting of real time transparent surfaces is still an unsolved problem.

For what you're doing you might want to look at implementing Weighted Blended OIT. This won't achieve the exact look you have above, but might get you something that's acceptably close.
http://jcgt.org/published/0002/02/09/

 

I forgot to thank you for the reply! Thank you and thank you for all the help you provide on these forums.