Shader "Cg shader for billboards"
{
Properties {
_MainTex ("Texture Image", 2D) = "white" {}
}
SubShader {

Tags {"Queue" = "Transparent"}

Pass {

ZWrite Off // don't write to depth buffer
// in order not to occlude other objects
Blend SrcAlpha OneMinusSrcAlpha
// blend based on the fragment's alpha value

CGPROGRAM

#pragma vertex vert
#pragma fragment frag

// User-specified uniforms
uniform sampler2D _MainTex;

struct vertexInput {
float4 vertex : POSITION;
float4 tex : TEXCOORD0;
};
struct vertexOutput {
float4 pos : SV_POSITION;
float4 tex : TEXCOORD0;
};

vertexOutput vert(vertexInput input)
{
vertexOutput output;

output.tex = input.tex;
output.pos = mul(UNITY_MATRIX_P, mul(UNITY_MATRIX_MV, float4(0.0, 0.0, 0.0, 1.0)) - float4(input.vertex.x, input.vertex.z, 0.0, 0.0));
return output;
}

float4 frag(vertexOutput input) : COLOR
{
return tex2D(_MainTex, float2(input.tex.xy));
}

ENDCG
}
}
}