#if OPENGL
    #define VS_SHADERMODEL vs_3_0
    #define PS_SHADERMODEL ps_3_0
#else
    #define VS_SHADERMODEL vs_4_0_level_9_1
    #define PS_SHADERMODEL ps_4_0_level_9_1
#endif

float4x4 World;
float4x4 View;
float4x4 Projection;
float4x4 InverseWorldView;
float FarClip;

Texture2D DecalTexture;
sampler DecalSampler = sampler_state {
    Texture = (DecalTexture);
    MagFilter = Linear;
    MinFilter = Linear;
    AddressU = Clamp;
    AddressV = Clamp;
};

Texture2D Depth;
sampler DepthSampler = sampler_state {
    texture = (Depth);
    magfilter = POINT;
    minfilter = POINT;
    mipfilter = POINT;
    AddressU = Clamp;
    AddressV = Clamp;
};

struct VertexShaderInput
{
    float4 Position : SV_POSITION;
};

struct VertexShaderOutput
{
    float4 Position : SV_POSITION;
    float4 PositionCS : TEXCOORD0;
    float4 PositionVS : TEXCOORD1;
};

VertexShaderOutput MainVS(in VertexShaderInput input)
{
    VertexShaderOutput output = (VertexShaderOutput)0;
    //float4 viewPosition = mul(input.Position, WorldView);
    float4 worldPosition = mul(input.Position, World);
    float4 viewPosition = mul(worldPosition, View);

    output.Position = mul(viewPosition, Projection);
    output.PositionCS = output.Position;
    output.PositionVS = viewPosition;

    return output;
}

float4 MainPS(VertexShaderOutput input) : COLOR
{
    //read depth, use point sample or load
    //float depth = DepthSampler.Load(int3(input.Position.xy, 0)).r;
    float depth = tex2D(DepthSampler, input.Position.xy).r;

    //Basically extend the depth of this ray to the end of the far plane, this gives us the position of the sphere only
    float3 cameraDirVS = input.PositionVS.xyz * (FarClip / -input.PositionVS.z);

    //compute ViewSpace position
    float3 positionVS = depth * cameraDirVS;

    //Transform to box space
    float3 positionOS = mul(float4(positionVS, 1), InverseWorldView).xyz;

    clip(1 - abs(positionOS.xyz));

    float2 textureCoordinate = (positionOS.xy + 1) / 2;

    //return DecalSampler.Sample(DecalSampler, textureCoordinate);
    return float4(1, 0, 0, 1);
}

technique BasicColorDrawing
{
    pass P0
    {
        VertexShader = compile VS_SHADERMODEL MainVS();
        PixelShader = compile PS_SHADERMODEL MainPS();
    }
};