/*
===========================================================================

Doom 3 BFG Edition GPL Source Code
Copyright (C) 1993-2012 id Software LLC, a ZeniMax Media company. 

This file is part of the Doom 3 BFG Edition GPL Source Code ("Doom 3 BFG Edition Source Code").  

Doom 3 BFG Edition Source Code is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Doom 3 BFG Edition Source Code is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Doom 3 BFG Edition Source Code.  If not, see <http://www.gnu.org/licenses/>.

In addition, the Doom 3 BFG Edition Source Code is also subject to certain additional terms. You should have received a copy of these additional terms immediately following the terms and conditions of the GNU General Public License which accompanied the Doom 3 BFG Edition Source Code.  If not, please request a copy in writing from id Software at the address below.

If you have questions concerning this license or the applicable additional terms, you may contact in writing id Software LLC, c/o ZeniMax Media Inc., Suite 120, Rockville, Maryland 20850 USA.

===========================================================================
*/

#include "global.inc"

uniform sampler2D samp0 : register(s0);   // view color
uniform sampler2D samp1 : register(s1);   // view depth

struct PS_IN {
	float2 texcoord0 : TEXCOORD0_centroid;
};

struct PS_OUT {
	float4 color : COLOR;
};

void main( PS_IN fragment, out PS_OUT result ) {
#if 0
    if ( fragment.texcoord0.x < 0.5 ) {
    // only draw on half the screen for comparison
        discard;
    }
#endif
	// don't motion blur the hands, which were drawn with alpha = 0
	if ( tex2D( samp0, fragment.texcoord0 ).w == 0.0 ) {
		discard;
	}

	// derive clip space from the depth buffer and screen position
	float windowZ = tex2D( samp1, fragment.texcoord0 ).x;
	float3 ndc = float3( fragment.texcoord0 * 2.0 - 1.0, windowZ * 2.0 - 1.0 );
	float clipW = -rpProjectionMatrixZ.w / ( -rpProjectionMatrixZ.z - ndc.z );

	float4 clip = float4( ndc * clipW, clipW );

	// convert from clip space this frame to clip space previous frame
	float4 reClip;
	reClip.x = dot( rpMVPmatrixX, clip );
	reClip.y = dot( rpMVPmatrixY, clip );
	reClip.z = dot( rpMVPmatrixZ, clip );
	reClip.w = dot( rpMVPmatrixW, clip );

	// convert to NDC values
	float2 prevTexCoord;
	prevTexCoord.x = ( reClip.x / reClip.w ) * 0.5 + 0.5;
	prevTexCoord.y = ( reClip.y / reClip.w ) * 0.5 + 0.5;

	// sample along the line from prevTexCoord to fragment.texcoord0

	float2 texCoord = prevTexCoord; //fragment.texcoord0;
	float2 delta = ( fragment.texcoord0 - prevTexCoord );

	float3 sum = float3( 0.0 );
	float goodSamples = 0;
	float samples = rpOverbright.x;

	for ( float i = 0 ; i < samples ; i = i + 1 ) {
		float2 pos = fragment.texcoord0 + delta * ( ( i / ( samples - 1 ) ) - 0.5 );
		float4 color = tex2D( samp0, pos );
		// only take the values that are not part of the weapon
		sum += color.xyz * color.w;
		goodSamples += color.w;
	}
	float invScale = 1.0 / goodSamples;

	result.color = float4( sum * invScale, 1.0 );
}
