//--------------------------------------------------------------------------------------
// Shader resources
//--------------------------------------------------------------------------------------

Buffer<float> g_Height;
Texture2D   g_Normal;
Texture2D   g_Diffuse; // Material albedo for diffuse lighting


//--------------------------------------------------------------------------------------
// Constant buffers
//--------------------------------------------------------------------------------------

cbuffer cbConstant
{
    float4  g_LightDir; // Object space
	int g_TerrainRes;
	int g_TerrainQuadRes;
};

cbuffer cbChangesEveryFrame
{
    matrix  g_World;
    matrix  g_WorldViewProjection;
    float   g_Time;
};

cbuffer cbUserChanges
{
};


//--------------------------------------------------------------------------------------
// Structs
//--------------------------------------------------------------------------------------

struct PosNorTex
{
    float4 Pos : SV_POSITION;
    float4 Nor : NORMAL;
    float2 Tex : TEXCOORD;
};

struct PosTexLi
{
    float4 Pos : SV_POSITION;
    float2 Tex : TEXCOORD;
    float   Li : LIGHT_INTENSITY;
};

struct PosTex
{
    float4 Pos : SV_POSITION;
    float2 Tex : TEXCOORD;
};

//--------------------------------------------------------------------------------------
// Samplers
//--------------------------------------------------------------------------------------

SamplerState samAnisotropic
{
    Filter = ANISOTROPIC;
    AddressU = Wrap;
    AddressV = Wrap;
};

SamplerState samLinearClamp
{
    Filter = MIN_MAG_MIP_LINEAR;
    AddressU = Clamp;
    AddressV = Clamp;
};

//--------------------------------------------------------------------------------------
// Rasterizer states
//--------------------------------------------------------------------------------------

RasterizerState rsDefault {
};

RasterizerState rsCullFront {
    CullMode = Front;
};

RasterizerState rsCullBack {
    CullMode = Back;
};

RasterizerState rsCullNone {
	CullMode = None; 
};

RasterizerState rsLineAA {
	CullMode = None; 
	AntialiasedLineEnable = true;
};


//--------------------------------------------------------------------------------------
// DepthStates
//--------------------------------------------------------------------------------------
DepthStencilState EnableDepth
{
    DepthEnable = TRUE;
    DepthWriteMask = ALL;
    DepthFunc = LESS_EQUAL;
};

BlendState NoBlending
{
    AlphaToCoverageEnable = FALSE;
    BlendEnable[0] = FALSE;
};


//--------------------------------------------------------------------------------------
// Shaders
//--------------------------------------------------------------------------------------

PosTexLi SimpleVS(PosNorTex Input) {
    PosTexLi output = (PosTexLi) 0;

    // Transform position from object space to homogenious clip space
    output.Pos = mul(Input.Pos, g_WorldViewProjection);

    // Pass trough normal and texture coordinates
    output.Tex = Input.Tex;

    // Calculate light intensity
    float3 n = normalize(mul(Input.Nor, g_World).xyz); // Assume orthogonal matrix
    output.Li = dot(n, g_LightDir.xyz);
        
    return output;
}

float4 SimplePS(PosTexLi Input) : SV_Target0 {
    // Perform lighting in object space, so that we can use the input normal "as it is"
    float4 matDiffuse = g_Diffuse.Sample(samAnisotropic, Input.Tex);
    return float4(matDiffuse.rgb * Input.Li, 1);
}

PosTex TerrainVS(uint VertexID : SV_VertexID) {
    PosTex output = (PosTex) 0;

	uint quadIdx = VertexID / 6;

	uint inQuadIdx = VertexID % 6;

	int2 coords;
	coords.x = VertexID % g_TerrainQuadRes;
	coords.y = VertexID / g_TerrainQuadRes;

	if (inQuadIdx == 1 || inQuadIdx == 4 || inQuadIdx == 5) coords.x++;
    if (inQuadIdx == 2 || inQuadIdx == 3 || inQuadIdx == 5) coords.y++;
	
	output.Tex.x = (float)coords.x / g_TerrainQuadRes;
	output.Tex.y = (float)coords.y / g_TerrainQuadRes;

	float height = g_Height[coords.x + coords.y * g_TerrainRes];
		
	output.Pos.x = (float)output.Tex.x;
	output.Pos.y = (float)output.Tex.y;
	output.Pos.z = height;
	output.Pos.w = 1.0F;

	mul(output.Pos, g_WorldViewProjection);

    return output;
}

float4 TerrainPS(PosTex Input) : SV_Target0 {
	float3 n;

    n.xy = g_Normal.Sample(samAnisotropic, Input.Tex);
	n.xy = n.xy * 2 - 1;

	n.z = sqrt(1.0 - n.x * n.x - n.y * n.y);

    float3 matDiffuse = g_Diffuse.Sample(samAnisotropic, Input.Tex);

	float i = dot(n, g_LightDir);
	i = saturate(i);

	return float4(matDiffuse.rgb * i, 1);
}


//--------------------------------------------------------------------------------------
// Techniques
//--------------------------------------------------------------------------------------
technique11 Render
{
    pass P0
    {
        SetVertexShader(CompileShader(vs_4_0, TerrainVS()));
        SetGeometryShader(NULL);
        SetPixelShader(CompileShader(ps_4_0, TerrainPS()));
        
        SetRasterizerState(rsCullNone);
        SetDepthStencilState(EnableDepth, 0);
        SetBlendState(NoBlending, float4(0.0f, 0.0f, 0.0f, 0.0f), 0xFFFFFFFF);
    }
}