unity world reconstruction

sampler2D _CameraNormalsTexture;
float4x4 _CameraToWorld;

v2f vert (appdata v)
{
	v2f o;
	o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
	o.uv = ComputeScreenPos (o.pos);
	o.ray = mul (UNITY_MATRIX_MV, v.vertex).xyz * float3(-1,-1,1);
	
	// v.normal contains a ray pointing from the camera to one of near plane's
	// corners in camera space when we are drawing a full screen quad.
	// Otherwise, when rendering 3D shapes, use the ray calculated here.
	o.ray = lerp(o.ray, v.normal, _LightAsQuad);
	
	return o;
} 

fixed4 frag (v2f i) : SV_Target
{
	float depth = SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture, uv);
	depth = Linear01Depth (depth);
	float4 vpos = float4(i.ray * depth,1);
	float3 wpos = mul (_CameraToWorld, vpos).xyz;
}

Excerpt from Internal-PrePassLighting.shader (available at e.g. http://download.unity3d.com/download_unity/builtin_shaders-4.5.4.zip )