Shader "Y-axis Billboard"
{
Properties
{
_MainTex ("Texture Image", 2D) = "white" {}
}

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

Pass
{
Blend SrcAlpha OneMinusSrcAlpha

CGPROGRAM
#pragma vertex vert
#pragma fragment frag

sampler2D _MainTex;

struct vertexInput
{
float4 vertex : POSITION;
float2 tex : TEXCOORD0;
};

struct vertexOutput
{
float4 pos : SV_POSITION;
float2 tex : TEXCOORD0;
};

vertexOutput vert(vertexInput input)
{
vertexOutput output;

float2 direct = normalize(
_WorldSpaceCameraPos.xz + float2(_World2Object[0].w,
_World2Object[2].w)
);

float2x2 rotate = float2x2(
direct[1], direct.x,
-direct.x, direct[1]
);

output.pos.xz = mul(rotate, input.vertex.xz);
output.pos.yw = input.vertex.yw;

output.pos = mul(UNITY_MATRIX_MVP, output.pos);
output.tex = input.tex;

return output;
}


fixed4 frag(vertexOutput input) : COLOR
{
return tex2D(_MainTex, float2(input.tex));
}
ENDCG
}
}
}