///////////////////////////////////////////////////////////////////////////////
//
//      ##  ######
//       ######  ###
//  ## ###############        Shark 3D Engine (www.shark3d.com)
//   ########## # # #
//    ########                Copyright (c) 1996-2006 Spinor GmbH.
//   ######### # # #          All rights reserved.
//  ##   ##########
//      ##
//
///////////////////////////////////////////////////////////////////////////////

struct PS_INPUT
{
    float2 mainTexCoord: TEXCOORD0;
    float2 offsScale: TEXCOORD1;
};

///////////////////////////////////////////////////////////////////////////////

sampler tex0: register(s0);

///////////////////////////////////////////////////////////////////////////////
// Pixelshader
// Profile: 2x0

float4 main(PS_INPUT input): COLOR0
{
    float2 mainTexCoord = input.mainTexCoord;
    float2 offsScale = input.offsScale;

    // Use filtering for additional smoothing effect.
    // The source-texture should be a filter-texture.
    // The size (width resp. height) of the destination-texture
    // should be 2 or 4 smaller than the size of the source-texture.
    //
    // Pixel in target-texture: X
    //
    // Source-sampling positions: S
    //                          *---*
    // Pixel in source-texture: |   |
    //                          *---*
    //              downscaling by 2 or more
    // no downscaling
    //                  *---*---*---*---*
    // *---*---*---*    |   |   |   |   |
    // | S |   | S |    *---S---*---S---*    
    // *---*---*---*    |   |   |   |   |    
    // |   | X |   |    *---*---X---*---*    
    // *---*---*---*    |   |   |   |   |    
    // | S |   | S |    *---S---*---S---*    
    // *---*---*---*    |   |   |   |   |    
    //                  *---*---*---*---*
    //
    // Note: Since this filter cannot sample more than a 4x4 neighbourhood,
    // downscaling factor of 4 cannot be exceeded without skipping pixels.
    // With downsampling of 1 or less filtering can't be used for smoothing
    // because it results in an undesirable filter pattern.
    // Thus a scaling factor of 2 or 4 is recommanded.
    
    const float2 offsPix0 = float2(-1.0f,-1.0f);
    const float2 offsPix1 = float2( 1.0f,-1.0f);
    const float2 offsPix2 = float2(-1.0f, 1.0f);
    const float2 offsPix3 = float2( 1.0f, 1.0f);

    // neighbour texture coordinates:
    float2 neigh0 = offsScale * offsPix0 + mainTexCoord.xy;
    float2 neigh1 = offsScale * offsPix1 + mainTexCoord.xy;
    float2 neigh2 = offsScale * offsPix2 + mainTexCoord.xy;
    float2 neigh3 = offsScale * offsPix3 + mainTexCoord.xy;

    float4 avg =
        (tex2D(tex0, neigh0)
        + tex2D(tex0, neigh1)
        + tex2D(tex0, neigh2)
        + tex2D(tex0, neigh3)) * 0.25;
    return clamp(avg - 0.8, 0.0, 1.0) * 5.0; // STD
}

///////////////////////////////////////////////////////////////////////////////