さまざまなズーム レベルにわたってマンデルブロ セットの色の鮮やかさを維持するにはどうすればよいですか?

// Vertex Shader
layout(location = 0) in vec2 pos;
out vec2 p;
void main()
{
    p = pos;
    gl_Position = vec4(pos, 0.0, 1.0);
}

// Fragment Shader
uniform vec2 p0;
uniform float zoom;
uniform int n;
uniform int sh;
uniform int multipass;
in vec2 p;
out vec4 col;

// Compute fractional iteration count
float mu = m + frac = n + 1 - log(log(sqrt(xx + yy)) / log(2.0));
mu *= float(1 << sh);
int i = int(mu);

// Multi-pass coloring
if (multipass != 0)
{
    // Quantize color based on iterations
    float r = (i >> 0) & 255; r /= 255.0;
    float g = (i >> 8) & 255; g /= 255.0;
    float b = (i >> 16) & 255; b /= 255.0;
    col = vec4(r, g, b, 255);
}
// Visible spectrum color gradient
else
{
    float q = float(i) / float(N);
    q = pow(q, 0.2);
    col = vec4(spectral_color(400.0 + (300.0 * q)), 1.0);
}