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Created May 30, 2016 12:52
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 import scene, ui shadercode_text = ''' // Modified Mandelbrot code from shadertoy.com // https://www.shadertoy.com/view/XdtSRN // used make_color function from ccc (pythonista forum) // https://github.com/cclauss/fractal_hacks/blob/master/cc_mandelbrot.py precision highp float; varying vec2 v_tex_coord; uniform sampler2D u_texture; uniform float u_time; uniform vec2 u_sprite_size; uniform vec2 u_offset; uniform float u_scale; int mandelbrot(vec2 uv) { vec2 z = vec2(0.0, 0.0); for (int i = 0; i < 64; i++) { // dot(z, z) > 4.0 is the same as length(z) > 2.0, but perhaps faster. if (dot(z, z) > 4.0) return i; // (x+yi)^2 = (x+yi) * (x+yi) = x^2 + (yi)^2 + 2xyi = x^2 - y^2 + 2xyi z = vec2(z.x * z.x - z.y * z.y, 2.0 * z.x * z.y) + uv; } return 0; } vec3 make_color(int i) { if (i == 0) return vec3(0.0,0.0,0.0); else if (i < 64) return vec3(float(i*4+128),float(i*4), 0.0)/255.0; else if ( i < 128) return vec3(64.0, 255.0, float((i-64)*4))/255.0; else if (i < 192) return vec3(64.0,float(255-(i-128)*4), 255.0)/255.0; else return vec3(64.0,0.0,float(255-(i-192)*4))/255.0; } void main(void) { // Screen coordinate, roughly -2 to +2 float ar = u_sprite_size.x / u_sprite_size.y; vec2 uv = vec2((v_tex_coord.x-0.5)*4.0*ar, (v_tex_coord.y-0.5)*4.0) ; // Evaluate mandelbrot for this coordinate. int ret = mandelbrot(uv); // Turn the iteration count into a color. //gl_FragColor = vec4(sin(vec3(0.1, 0.2, 0.5) * float(ret)), 1); gl_FragColor = vec4(make_color(ret), 1.0); } ''' class MyScene (scene.Scene): def setup(self): self.sprite = scene.SpriteNode(size=self.size, parent=self) self.sprite.shader = scene.Shader(shadercode_text) self.sprite.anchor_point = (0, 0) def did_change_size(self): self.sprite.size = self.size scene.run(MyScene(), show_fps=True)

### cclauss commented May 30, 2016 • edited

@omz Is it possible to make it even more fullscreen?

This is what my comments on the original gist do.

Also, if you increase the MAX_TRIES (second line of `mandelbrot()`) from 64 up to 256 you get slightly better colors at the edge of the set but performance on my iPad dropped to about 30fps. Still it is stunning performance. I believe that MAX_TRIES might become more important the further you zoom into the set. 