gistfile1.txt

import sys

class IndentOutput:
    def __init__(self, backend):
        self.level = 0
        self.backend = backend
        self.buffer = ""
    def indent(self):
        self.level += 1
    def dedent(self):
        self.level -= 1
    def __enter__(self):
        self.indent()
    def __exit__(self, exc_type, exc_value, traceback):
        self.dedent()
    def write(self, s):
        self.buffer += s
        if s == '\n':
            for p in self.buffer.splitlines():
                print("    " * self.level + p, file=self.backend)
            self.buffer = ""

n = 8
o = IndentOutput(sys.stdout)
sys.stdout = o

print("#version 400 core")
print("#extension GL_ARB_gup_shader_fp64 : enable")
print()
print("in vec2 txcoords;")
print("uniform double zoom;")
print("uniform dvec2 offset;")
print("out vec4 fragColor;")
print("uniform int iter;")
print()
print("uniform sampler1D palette;")
print()
print("void main() {")
with o:
    print("double c_real = double(txcoords.x) * zoom + offset.x;")
    print("double c_imag = double(txcoords.y) * zoom + offset.y;")
    print("double z_real_0 = c_real;")
    print("double z_imag_0 = c_imag;")
    for i in range(1, n):
        print("double z_real_{0} = z_real_{1} * z_real_{1} - z_imag_{1} * z_imag_{1} + c_real;".format(i, i-1))
        print("double z_imag_{0} = 2.0 * z_real_{1} * z_imag_{1} + c_imag;".format(i, i-1))
    print("int i;")
    print("for (i = 0; i < iter; i += {})".format(n), "{")
    with o:
        print("double z_r_q = z_real_{0} * z_real_{0};".format(n - 1))
        print("double z_i_q = z_imag_{0} * z_imag_{0};".format(n - 1))
        print("if (z_i_q + z_r_q > 4.0) {")
        with o:
            print("break;")
        print("}")
        for i in range(n):
            src = i - 1
            if src < 0:
                src = n - 1
            if i == 0:
                print("z_real_0 = z_r_q - z_i_q + c_real;")
            else:
                print("z_real_{0} = z_real_{1} * z_real_{1} - z_imag_{1} * z_imag_{1} + c_real;".format(i, src))
            print("z_imag_{0} = 2.0 * z_real_{1} * z_imag_{1} + c_imag;".format(i, src))
    print("}")
    for i in range(n - 1):
        if i == 0:
            print("if ", end='')
        else:
            print("} else if ", end='')
        print("(z_imag_{0} * z_imag_{0} + z_real_{0} * z_real_{0} > 4.0)".format(i), "{")
        with o:
            print("i -= {};".format(n - i - 1))
            print("z_real_{0} = z_real_{1};".format(n - 1, i))
            print("z_imag_{0} = z_imag_{1};".format(n - 1, i))
    print("}")
    print("if (i == iter) {")
    with o:
        print("fragColor = vec4(0.0, 0.0, 0.0, 1.0);")
    print("} else {")
    with o:
        print("float ni = float(i) + 1.0 - log(log(float(sqrt(z_imag_{0} * z_imag_{0} + z_real_{0} * z_real_{0})))) / log(2.0);".format(n - 1))
        print("fragColor = texture(palette, abs(ni / float(iter)));")
    print("}")
print("}")