Question Using tranformation matrixes with GPU instancing

I'm trying to apply a billboard shader to meshes drew on top of a terrain with DrawMeshInstancedIndirect, but I can't find a way to make it work. The compute buffer contains a 4x4Matrix,with position, rotation and scale, and the normal. It looks like the built in matrixes are relative to a mesh drew at the terrain origin, even though if I replace o.vertex with UnityObjectToClipPos(pos) it works fine (without the effect). I've tried different techniques but all give the same result. I'm using urp.
Any help is appreciated!

Current result



Shader

Code (CSharp):

1. Shader "Custom/InstancedIndirectGrass" {
2.     Properties
3.     {
4.         _MainTex ("Texture", 2D) = "white" {}
5.     }
6.     SubShader {
7.         Tags { "RenderType" = "Opaque" }
8.         LOD 100
9.  
10.         Pass {
11.             ZTest On
12.             Cull Off
13.  
14.             CGPROGRAM
15.             #pragma vertex vert
16.             #pragma fragment frag
17.  
18.             #include "UnityCG.cginc"
19.  
20.             struct appdata_t {
21.                 float4 vertex   : POSITION;
22.                 float4 color    : COLOR;
23.                 float3 normal   : NORMAL;
24.                 float2 uv       : TEXCOORD0;
25.             };
26.  
27.             struct v2f {
28.                 float4 vertex   : SV_POSITION;
29.                 fixed4 color    : COLOR;
30.                 float3 normal   : NORMAL;
31.                 float2 uv       : TEXCOORD0;
32.             };
33.  
34.             struct MeshProperties {
35.                 float4x4 mat;
36.                 float3 normal;
37.             };
38.  
39.             StructuredBuffer<MeshProperties> _Properties;
40.  
41.             Texture2D _MainTex;
42.             SamplerState sampler_MainTex;
43.             float4 _MainTex_ST;
44.  
45.             v2f vert(appdata_t i, uint instanceID: SV_InstanceID) {
46.                 v2f o;
47.                 // data
48.                 float4 pos = mul(_Properties[instanceID].mat, i.vertex);
49.                
50.                 float4 worldOrigin = mul(unity_ObjectToWorld, float4(0, 0, 0, 1));
51.                 float4 viewOrigin = float4(UnityObjectToViewPos(float3(0, 0, 0)), 1);
52.                
53.                 // Billboard effect
54.                 float4 worldPosition = mul(unity_ObjectToWorld, pos);
55.                 // Removed rotation
56.                 float4 viewPosition = worldPosition - worldOrigin + viewOrigin;
57.                 float4 clipPosition = mul(UNITY_MATRIX_P, viewPosition);
58.  
59.                 o.vertex = clipPosition;
60.  
61.                 o.normal = _Properties[instanceID].normal;
62.                 o.uv = TRANSFORM_TEX(i.uv, _MainTex);
63.                
64.                 return o;
65.             }
66.  
67.             fixed4 frag(v2f i) : SV_Target {
68.                 fixed4 col = _MainTex.Sample(sampler_MainTex, i.uv);
69.                 clip(col.a - 0.5);
70.                 return col;
71.             }
72.  
73.             ENDCG
74.         }
75.     }
76. }

 

I fixed it, it was my fault. I had to change worldOrigin and viewOrigin using the mesh origin position, which I added to the buffer.