JS1k: The JavaScript code golfing competition

/* TODO: minify. LOL! */
_='F="pGcis lowp fE;unifm 
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')with(_.split($[Y]))_=join(pop());eval(_)

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

const VERTEX_SHADER = [
	'attribute vec4 p;',
	'void main(void)',
	'{',
	'	gl_Position = p;',
	'}'
].join('\n')

const FRAGMENT_SHADER = [
	'precision lowp float;',
	'uniform float t;',
	'float make_box(vec3 p, vec3 b)',
	'{',
	'	return length(max(abs(p) - b, 0.));',
	'}',
	'void main(void)',
	'{',
	'	vec2 coords = gl_FragCoord.xy / 256.;',
	'	float u = .1 * (t - pow(coords.x - .5, 2.) - pow(coords.y - .5, 2.));',
	'	float sin_u = sin(u);',
	'	float cos_u = cos(u);',
	'	float cos_3u = cos(3. * u);',
	'	vec3 ray_dir = normalize(vec3(coords.x + .2 * cos_u, coords.y - .5, .2 * sin_u - 1.));',
	'	vec3 ray_orig = vec3(-100. * cos_u * cos_3u + 50., 5., -100. * sin_u * cos_3u - 50.);',
	'	float offs = 40.;',
	'	float j;',
	'	for (float i = 0.; i < 500.; i += 1.)',
	'	{',
	'		vec3 pos = vec3(ray_orig + ray_dir * offs);',
	'		vec3 c = vec3(100., 100., 100.);',
	'		vec3 q = mod(pos, c) - .5 * c;',
	'		float dist = min(make_box(q, vec3(50., 1., 50.)),',
	'				 min(make_box(q, vec3(5.5, 5., 5.5)),',
	'				     length(q.xz) - 5.));',
	'		offs += dist;',
	'		j = i;',
	'		if (abs(dist) < .0001)',
	'		{',
	'			break;',
	'		}',
	'	}',
	'	gl_FragColor = vec4(.02 * j * (vec3(.38, .49, .55) + .2 * abs(cos(20. * u)) + .2), 1.);',
	'}'
].join('\n')

main()

function main() {
	g.viewport(0, 0, 256, 256)
	a.height = a.width = 256
	p = link(VERTEX_SHADER, FRAGMENT_SHADER)

	g.enableVertexAttribArray(g.bindBuffer(g.ARRAY_BUFFER, g.createBuffer()))
	g.bufferData(g.ARRAY_BUFFER, new Float32Array([1, 1, 1, -3, -3, 1]), g.STATIC_DRAW)
	g.vertexAttribPointer(0, 2, g.FLOAT, false, 0, 0)

	t = 0
	render()
}

function render() {
	requestAnimationFrame(render)
	g.uniform1f(g.getUniformLocation(p, 't'), t += 0.01)
	g.drawArrays(g.TRIANGLES, 0, 3)
}

function compile(shader_source, shader_type) {
	var shader = g.createShader(shader_type)
	g.shaderSource(shader, shader_source)
	g.compileShader(shader)
	// <debug>
	var worked = g.getShaderParameter(shader, g.COMPILE_STATUS)
	if (!worked)
		throw Error('compile() combusted spontaneously and violently:\n' +
			    g.getShaderInfoLog(shader))
	// </debug>
	return shader
}

function link(vertex_shader, fragment_shader) {
	var program = g.createProgram()
	g.attachShader(program, compile(vertex_shader, g.VERTEX_SHADER))
	g.attachShader(program, compile(fragment_shader, g.FRAGMENT_SHADER))
	g.linkProgram(program)
	// <debug>
	var worked = g.getProgramParameter(program, g.LINK_STATUS)
	if (!worked)
		throw Error('link() combusted spontaneously and violently:\n' +
			    g.getProgramInfoLog(program))
	// </debug>
	g.useProgram(program)
	return program
}