#define cx_mul(a,b) vec2(a.x*b.x-a.y*b.y, a.x*b.y+a.y*b.x)
#define cx_mag2(x) dot(x,x)

#define E 2.718281828

uniform int maxiter;
uniform float escape2;

in vec2 base;
in vec2 delta;

layout(location = 0) out vec4 diffuseColor;

void main() {
    vec2 pos = base;
    int i;
    for (i = 0; i < maxiter; i++) {
        if (cx_mag2(pos) > escape2) {
            break;
        }
        pos = cx_mul(pos, pos) + delta;
    }
    float mag = cx_mag2(pos);
    float sm_color = log(log(mag / 2.)) / log(escape2) * 2;

    float shade = i - 1 + sm_color;
    // TODO: palette mapping
    diffuseColor = vec4(shade, shade, shade, 1);
}