// Mandelbrot Shader effect file
// (C) Copyright 2003 by John H. Palevich

string XFile = "teapot.x";
int    BCLR  = 0xff202080;

// transformations

float4x3 WorldView  : WORLDVIEW;
float4x4 Projection : PROJECTION;

#define MANDEL_STEPS 11
int TEXTURESCALE = 2.0;

struct VS_OUTPUT
{
    float4 Pos  : POSITION;
    float2 Tex0 : TEXCOORD0;               
};

VS_OUTPUT VS(    
    float3 Pos  : POSITION,
    float3 Norm : NORMAL)
{
    VS_OUTPUT Out = (VS_OUTPUT)0;

    float3 P = mul(float4(Pos, 1), (float4x3)WorldView);    // position (view space)
 
    Out.Pos  = mul(float4(P, 1), Projection);             // position (projected)

    Out.Tex0.x = Pos.z;    // Compute Tex0 U and V from position.
    Out.Tex0.y = Pos.x;
    Out.Tex0 *= TEXTURESCALE;       

    return Out;
}

float2 MandelbrotStep(float2 a, float2 t0) : COLOR
{
    float2 result;
    float2 a2 = a * a;
    result.x = a2.x - a2.y;
    result.y = a.x * a.y * 2;
    result += t0;
    return result;
}

float4 PS20(VS_OUTPUT In) : COLOR
{   
    float4 Color;
    Color.rg = In.Tex0;
    Color.b = 0;
    Color.a = 1;

    int i;
    for(int i = 0; i < MANDEL_STEPS; i++)
    {
        Color.rg = MandelbrotStep(Color.rg, In.Tex0);
    }
#ifdef CLAMP_COLORS
    // Clamping is required if you want the output to look the
    // same on both the Ref-Rast and the ATI 9700.
    // But I've commented it out because it ends up
    // getting rid of the beautiful stripe fringe effect around
    // the main Mandelbrot pattern. (I guess RefRast
    // and the ATI card do different things when handleing floating point overflow.
    // Maybe it's the difference between 24-bit floating point and 32-bit floating point?

    float dist = Color.x * Color.x + Color.y * Color.y;
    return dist > 2.0 ? 0.3 : Color; // Replace color fringe pattern with boring grey.
#else
    return Color;
#endif
}

technique TMandelbrot_PS_2_0
{
    pass P0
    {
        VertexShader = compile vs_1_1 VS();
        PixelShader  = compile ps_2_0 PS20();
    }
}