//========== Copyright (c) Valve Corporation, All rights reserved. ==========//

sampler g_sDepth		: register( s0 );
float4x4 g_mInvVP		: register( c0 );
float2 g_vInvScreenSize	: register( c4 );

struct PS_INPUT
{
#ifdef _X360
	float2 vPos : VPOS;
#else
	float2 uv	: TEXCOORD0;
#endif

};

struct PSOutput
{
	float4 vColor	: COLOR0;
	float  fDepth	: DEPTH;
};

PSOutput main( PS_INPUT i)
{
#ifdef _X360
	float2 vUV = 4.0 * i.vPos + 0.5;
	vUV *= g_vInvScreenSize;
#else
	float2 vUV = i.uv;
#endif

	float4 vDepths;
	vDepths.x = tex2D( g_sDepth, vUV );
	vDepths.y = tex2D( g_sDepth, vUV + float2(g_vInvScreenSize.x, 0.0) );
	vDepths.z = tex2D( g_sDepth, vUV + float2(0.0, g_vInvScreenSize.y) );
	vDepths.w = tex2D( g_sDepth, vUV + g_vInvScreenSize );

	// convert sample to world-space
	float4 vClipPos;
	vClipPos.xy = 2.0 * vUV.xy - 1.0;
	vClipPos.y = -vClipPos.y;
	vClipPos.z = 1.0 - vDepths.x;
	vClipPos.w = 1.0;
	float4 vWorldPos = mul( vClipPos, g_mInvVP );
	vWorldPos /= vWorldPos.w;

	// Derive normal from depth buffer. Ideally I'd compute a world space pos from vDepths.x, y, and z and then cross the deltas of that,
	// but that's a lot of work.
	float3 vNormal = cross( ddx(vWorldPos.xyz), ddy(vWorldPos.xyz) );

	PSOutput o;

	// TODO: output normal
	o.vColor = 1.0;//-vPos.x/320.0;//float4( 0.5 * vNormal + 0.5, 0.0 );

	// get max depth
	vDepths.xy = min( vDepths.xy, vDepths.zw );
	o.fDepth = min( vDepths.x, vDepths.y );
	//o.fDepth = dot( vDepths, float4( 0.25, 0.25, 0.25, 0.25 ) );

	return o;
}