From fda6aac3b4173d8cfae0656b4dbe2f72d689428b Mon Sep 17 00:00:00 2001
From: polyfloyd <floyd@polyfloyd.net>
Date: Sat, 19 May 2018 16:06:46 +0200
Subject: [PATCH] Add torus-thingy.glsl

---
 torus-thingy.glsl | 135 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 135 insertions(+)
 create mode 100644 torus-thingy.glsl

diff --git a/torus-thingy.glsl b/torus-thingy.glsl
new file mode 100644
index 0000000..62c921b
--- /dev/null
+++ b/torus-thingy.glsl
@@ -0,0 +1,135 @@
+/*
+ * License Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
+ * Created by bal-khan
+ */
+
+vec2 march(vec3 pos, vec3 dir);
+vec3 camera(vec2 uv);
+void rotate(inout vec2 v, float angle);
+vec3 calcNormal( in vec3 pos, float e, vec3 dir);
+float loop_circle(vec3 p);
+float circle(vec3 p, float phase);
+float sdTorus( vec3 p, vec2 t, float phase );
+float mylength(vec2 p);
+float nrand( vec2 n );
+
+float  t;   // time
+vec3 ret_col; // torus color
+vec3 h;    // light amount
+
+#define I_MAX  200.
+#define E   0.00001
+#define FAR   15.
+#define PI   3.14
+
+void mainImage(out vec4 c_out, in vec2 f)
+{
+	t  = iTime*.125;
+	vec3 col = vec3(0., 0., 0.);
+	vec2 R = iResolution.xy,
+		 uv  = vec2(f-R/2.) / R.x;
+	vec3 dir = camera(uv);
+	vec3 pos = vec3(.0, .0, 0.0);
+
+	pos.z = 4.5+1.5*sin(t*10.);
+	h*=0.;
+	vec2 inter = (march(pos, dir));
+	if (inter.y <= FAR)
+		col.xyz = ret_col*(1.-inter.x*.0025);
+	else
+		col *= 0.;
+	col += h*.005125;
+	c_out =  vec4(col,1.0);
+}
+
+float scene(vec3 p)
+{
+	float var;
+	float mind = 1e5;
+	p.z += 2.;
+	rotate(p.xz, 1.57-.5*iTime);
+	rotate(p.yz, 1.57-.5*iTime);
+	vec2 q = vec2(mix(mylength(p.xy), length(p.xy), abs(sin(iTime)) )-2.,p.z);
+	var = atan(p.x,p.y);
+	rotate(q, var+iTime*2.);
+	q = abs(q)-.5;
+	rotate(q, var*-3.+iTime*2.);
+	var = cos(floor(var*6.)*.5+iTime*3. );
+	ret_col = 1.-vec3(.5-var*.5, .5, .3+var*.5);
+	mind = mylength(q)-.125-.1*var;
+	h += vec3(.5,.8,.5)*(var!=0.?0.:1.)*vec3(1.)*.0125/(.01+(mind-var*.1)*(mind-var*.1) );
+	h += vec3(.5,.8,.5)*(var!=0.?1.:0.)*vec3(1.)*.0125/(.01+mind*mind);
+
+	return (mind);
+}
+
+vec2 march(vec3 pos, vec3 dir)
+{
+	vec2 dist = vec2(0.0, 0.0);
+	vec3 p = vec3(0.0, 0.0, 0.0);
+	vec2 s = vec2(0.0, 0.0);
+
+	for (float i = -1.; i < I_MAX; ++i)
+	{
+		p = pos + dir * dist.y;
+		dist.x = scene(p);
+		dist.y += dist.x*.2; // makes artefacts disappear
+		if (dist.x < E || dist.y > FAR)
+		{
+			break;
+		}
+		s.x++;
+	}
+	s.y = dist.y;
+	return (s);
+}
+
+float mylength(vec2 p)
+{
+	float ret;
+
+	p = p*p*p*p;
+	p = p*p;
+	ret = (p.x+p.y);
+	ret = pow(ret, 1./8.);
+
+	return ret;
+}
+
+// Utilities
+
+void rotate(inout vec2 v, float angle)
+{
+	v = vec2(cos(angle)*v.x+sin(angle)*v.y,-sin(angle)*v.x+cos(angle)*v.y);
+}
+
+vec2 rot(vec2 p, vec2 ang)
+{
+	float c = cos(ang.x);
+	float s = sin(ang.y);
+	mat2 m = mat2(c, -s, s, c);
+
+	return (p * m);
+}
+
+vec3 camera(vec2 uv)
+{
+	float  fov = 1.;
+	vec3  forw  = vec3(0.0, 0.0, -1.0);
+	vec3     right = vec3(1.0, 0.0, 0.0);
+	vec3     up    = vec3(0.0, 1.0, 0.0);
+
+	return (normalize((uv.x) * right + (uv.y) * up + fov * forw));
+}
+
+vec3 calcNormal( in vec3 pos, float e, vec3 dir)
+{
+	vec3 eps = vec3(e,0.0,0.0);
+
+	return normalize(vec3(
+				march(pos+eps.xyy, dir).y - march(pos-eps.xyy, dir).y,
+				march(pos+eps.yxy, dir).y - march(pos-eps.yxy, dir).y,
+				march(pos+eps.yyx, dir).y - march(pos-eps.yyx, dir).y ));
+}
+
+// https://www.shadertoy.com/view/4lXBWj