//--------------------------------------------------------------------------------------
// LineDraw.hlsl - Used to solid lines for GameCode4 (D3D11 renderer)
//
// Part of the GameCode4 Application
//
// GameCode4 is the sample application that encapsulates much of the source code
// discussed in "Game Coding Complete - 4th Edition" by Mike McShaffry and David
// "Rez" Graham, published by Charles River Media. 
// ISBN-10: 1133776574 | ISBN-13: 978-1133776574
//
// If this source code has found it's way to you, and you think it has helped you
// in any way, do the authors a favor and buy a new copy of the book - there are 
// detailed explanations in it that compliment this code well. Buy a copy at Amazon.com
// by clicking here: 
//    http://www.amazon.com/gp/product/1133776574/ref=olp_product_details?ie=UTF8&me=&seller=
//
// There's a companion web site at http://www.mcshaffry.com/GameCode/
// 
// The source code is managed and maintained through Google Code: 
//    http://code.google.com/p/gamecode4/
//
// (c) Copyright 2012 Michael L. McShaffry and David Graham
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser GPL v3
// as published by the Free Software Foundation.
//
// This program 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 
// http://www.gnu.org/licenses/lgpl-3.0.txt for more details.
//
// You should have received a copy of the GNU Lesser GPL v3
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
//
//--------------------------------------------------------------------------------------

// This shader was originally posted here: http://www.gamedev.net/topic/609031-hlsl-line-geometry-shader/



Texture2D LineTexture;

//-----------------------------------------------------------------------------
// Constant Buffers
//-----------------------------------------------------------------------------
cbuffer cbRenderTarget
{
    float4 RenderTargetSize;			// x,y are the only ones used.
}

cbuffer cbChangePerFrame
{
    matrix WorldViewProjection;
}

cbuffer cbDiffuseColor
{
	float4 DiffuseColor;
}

//-----------------------------------------------------------------------------
// Shader Input / Output Structures
//-----------------------------------------------------------------------------
struct VS_INPUT
{
    float4 Position : POSITION0;
};

struct GEO_IN
{
    float4 Position : POSITION0;
};

struct GEO_OUT
{
    float4 Position : SV_POSITION;
    float2 TexCoord : TEXCOORD;
};

struct PS_OUTPUT 
{
    float4 Color : SV_Target0;
};

GEO_IN VS_LineV2(in VS_INPUT input)
{
    GEO_IN output;
    output.Position = mul(input.Position, WorldViewProjection);
    //output.Position = input.Position;
    return output;
}

[maxvertexcount(6)]
void GS(line GEO_IN points[2], inout TriangleStream<GEO_OUT> output)
{
    float4 p0 = points[0].Position;
    float4 p1 = points[1].Position;

    float w0 = p0.w;
    float w1 = p1.w;

    p0.xyz /= p0.w;
    p1.xyz /= p1.w;

    float3 line01 = p1 - p0;
    float3 dir = normalize(line01);

    // scale to correct window aspect ratio
    float3 ratio = float3(RenderTargetSize.y, RenderTargetSize.x, 0);
    ratio = normalize(ratio);

    float3 unit_z = normalize(float3(0, 0, -1));

    float3 normal = normalize(cross(unit_z, dir) * ratio);

    float width = 0.005;

    GEO_OUT v[4];

    float3 dir_offset = dir * ratio * width;
    float3 normal_scaled = normal * ratio * width;

    float3 p0_ex = p0 - dir_offset;
    float3 p1_ex = p1 + dir_offset;

    v[0].Position = float4(p0_ex - normal_scaled, 1) * w0;
    v[0].TexCoord = float2(0,0);

    v[1].Position = float4(p0_ex + normal_scaled, 1) * w0;
    v[1].TexCoord = float2(0,0);

    v[2].Position = float4(p1_ex + normal_scaled, 1) * w1;
    v[2].TexCoord = float2(0,0);

    v[3].Position = float4(p1_ex - normal_scaled, 1) * w1;
    v[3].TexCoord = float2(0,0);

    output.Append(v[2]);
    output.Append(v[1]);
    output.Append(v[0]);

    output.RestartStrip();

    output.Append(v[3]);
    output.Append(v[2]);
    output.Append(v[0]);

    output.RestartStrip();
}

PS_OUTPUT PS_LineV2(GEO_OUT input)
{
    PS_OUTPUT output;

    //output.Color = LineTexture.Sample(LinearSampler, input.TexCoord);
    //output.Color = float4(input.TexCoord.xy, 0, 1);
    output.Color = DiffuseColor;
	
    return output;
}

technique10 LineV2Technique
{
    pass P0
    {       
        SetVertexShader(CompileShader(vs_4_0, VS_LineV2()));
        SetGeometryShader(CompileShader(gs_4_0, GS()));
        SetPixelShader(CompileShader(ps_4_0, PS_LineV2()));
    }
}