Gradient Shader breaks on second instance

Hi guys,

I'm writing a gradient shader that lerps between 2 colors over time. It's all fine until I introduce a second instance of an object having a material with this shader. It works as expected in the scene view, but in-game something really weird happens - only one color appears. Also, when moving one of the objects down on the Y axis the second color starts to show.

What am I missing here? Also, I'm pretty new to writing shaders, is there a better approach?

Here's the shader itself:

Code (CSharp):

1. Shader "Shaders/Gradient Shader"
2. {
3.   Properties
4.   {
5.     _Color1 ("Color 1", Color) = (1, 1, 1, 1)
6.     _Color2 ("Color 2", Color) = (0, 0, 0, 0)
7.   }
8.   SubShader
9.   {
10.     Pass
11.     {
12.       CGPROGRAM
13.       #pragma vertex vert
14.       #pragma fragment frag
15.      
16.       #include "UnityCG.cginc"
17.  
18.       struct appdata
19.       {
20.         float4 vertex : POSITION;
21.       };
22.  
23.       struct v2f
24.       {
25.         float4 vertex : SV_POSITION;
26.         float wave : PSIZE0;
27.       };
28.  
29.       float4 _Color1;
30.       float4 _Color2;
31.      
32.       v2f vert (appdata v)
33.       {
34.         v2f o;
35.         o.vertex = UnityObjectToClipPos(v.vertex);
36.         o.wave = (v.vertex.y * (sin(_Time[3]) + 2)) * 2;
37.  
38.         return o;
39.       }
40.      
41.       fixed4 frag (v2f i) : SV_Target
42.       {
43.         float l = clamp(i.wave, 0 , 1);
44.         fixed4 col = lerp(_Color1, _Color2, l);
45.         return col;
46.       }
47.       ENDCG
48.     }
49.   }
50. }
51.  

Here's how things look when I duplicate the cube object in the scene:

 

This is caused by dynamic batching. When a mesh is batched, either dynamically or statically, Unity combines multiple meshes together into a single larger mesh with the vertex locations positioned in works space. So when you just have one object v.vertex.y = 0 is centered on the object, but as soon as you add the second Unity is batching them and v.vertex.y = 0 is now at the center of the world.

The options are disable batching on the shader, or don't use the vertex position and instead use a mesh with a custom additional UV channel.
https://docs.unity3d.com/Manual/SL-SubShaderTags.html

You can also try using an instanced shader.
https://docs.unity3d.com/Manual/GPUInstancing.html

 

Setting the DisableBatching tag to True worked great, thanks!