// Unimplemented uniforms
// Resolution doesn't make sense in the VR context
const vec3 iResolution = vec3(1.0);
// Mouse functions not enabled currently
const vec4 iMouse = vec4(0.0);
// No support for audio input
const float iSampleRate = 1.0;
// No support for video input
const vec4 iChannelTime = vec4(0.0);


uniform float iGlobalTime;                  // shader playback time (in seconds)
uniform vec4 iDate;
uniform int iFrameCount;
uniform vec3 iWorldPosition;                // the position of the object being rendered
uniform vec3 iWorldScale;                   // the dimensions of the object being rendered
uniform mat3 iWorldOrientation;             // the orientation of the object being rendered
uniform vec3 iChannelResolution[4];
uniform sampler2D iChannel0;
uniform sampler2D iChannel1;
uniform sampler2D iChannel2;
uniform sampler2D iChannel3;

// Redefine below to see the tiling...
//#define SHOW_TILING

#define TAU 6.28318530718
#define MAX_ITER 5

void mainImage( out vec4 fragColor, in vec2 fragCoord ) 
{
	float time = iGlobalTime * .5+23.0;
    // uv should be the 0-1 uv of texture...
	vec2 uv = fragCoord.xy / iResolution.xy;
    
#ifdef SHOW_TILING
	vec2 p = mod(uv*TAU*2.0, TAU)-250.0;
#else
    vec2 p = mod(uv*TAU, TAU)-250.0;
#endif
	vec2 i = vec2(p);
	float c = 1.0;
	float inten = .005;

	for (int n = 0; n < MAX_ITER; n++) 
	{
		float t = time * (1.0 - (3.5 / float(n+1)));
		i = p + vec2(cos(t - i.x) + sin(t + i.y), sin(t - i.y) + cos(t + i.x));
		c += 1.0/length(vec2(p.x / (sin(i.x+t)/inten),p.y / (cos(i.y+t)/inten)));
	}
	c /= float(MAX_ITER);
	c = 1.17-pow(c, 1.4);
	vec3 colour = vec3(pow(abs(c), 8.0));
    colour = clamp(colour + vec3(0.0, 0.35, 0.5), 0.0, 1.0);
    

	#ifdef SHOW_TILING
	// Flash tile borders...
	vec2 pixel = 2.0 / iResolution.xy;
	uv *= 2.0;

	float f = floor(mod(iGlobalTime*.5, 2.0)); 	// Flash value.
	vec2 first = step(pixel, uv) * f;		   	// Rule out first screen pixels and flash.
	uv  = step(fract(uv), pixel);				// Add one line of pixels per tile.
	colour = mix(colour, vec3(1.0, 1.0, 0.0), (uv.x + uv.y) * first.x * first.y); // Yellow line
	
	#endif
	fragColor = vec4(colour, 1.0);
}