From a8e731741191c38623ad20885bf80e2158abaaf5 Mon Sep 17 00:00:00 2001
From: rodri <rgl@antares-labs.eu>
Date: Tue, 2 Jun 2020 15:44:18 +0000
Subject: genesis.

---
 bcardrt.c | 113 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 mkfile    |   8 +++++
 2 files changed, 121 insertions(+)
 create mode 100644 bcardrt.c
 create mode 100644 mkfile

diff --git a/bcardrt.c b/bcardrt.c
new file mode 100644
index 0000000..57bd833
--- /dev/null
+++ b/bcardrt.c
@@ -0,0 +1,113 @@
+#include <u.h>
+#include <libc.h>
+
+typedef struct { double x, y, z; } vec;
+
+vec v(double x, double y, double z) { return (vec){x,y,z}; }
+vec vadd(vec a, vec b) { return v(a.x+b.x,a.y+b.y,a.z+b.z); }
+vec vmul(vec u, double s) { return v(u.x*s,u.y*s,u.z*s); }
+double vdot(vec a, vec b) { return a.x*b.x+a.y*b.y+a.z*b.z; }
+vec vcross(vec a, vec b) { return v(a.y*b.z-a.z*b.y,a.z*b.x-a.x*b.z,a.x*b.y-a.y*b.x); }
+vec vnorm(vec u) { return vmul(u,1/sqrt(vdot(u,u))); }
+
+/* aek */
+//int G[] = {247570, 280596, 280600, 249748, 18578, 18577, 231184, 16, 16};
+/* rgl */
+int G[] = {263948, 264338, 262288, 266128, 395408, 346256, 296720, 16, 16};
+
+double R(void) { return (double)rand() / 0x7ffffffd; }
+
+int
+TraceRay(vec src, vec dst, double *t, vec *normal)
+{
+	int m, k, j;
+	double p;
+
+	*t = 1e9;
+	m = 0;
+	p = -src.z / dst.z;
+	if(p > 0.01){
+		*t = p;
+		*normal = v(0,0,1);
+		m = 1;
+	}
+
+	for (k = 19; k--;)
+		for (j = 9; j--;)
+			if ((G[j] & 1<<k) != 0) {
+				vec p;
+				double b, c, q;
+
+				p = vadd(src, v(-k,0,-j - 4));
+				b = vdot(p, dst);
+				c = vdot(p, p) - 1;
+				q = b*b - c;
+	
+				if(q > 0){
+					double s;
+
+					s = -b - sqrt(q);
+					if(s > 0.01 && s < *t){
+						*t = s;
+						*normal = vnorm(vadd(p, vmul(dst, *t)));
+						m = 2;
+					}
+				}
+			}
+	return m;
+}
+
+vec
+Sample(vec src, vec dst)
+{
+	vec normal, intersection, light_dir, half_vec;
+	double t, lamb_f, color;
+	int match;
+
+	match = TraceRay(src, dst, &t, &normal);
+	if(!match)
+		return vmul(v(0.7,0.6,1), pow(1 - dst.z, 4));
+
+	intersection = vadd(src, vmul(dst, t));
+	light_dir = vnorm(vadd(v(9 + R(),9 + R(),16), vmul(intersection, -1)));
+	half_vec = vadd(dst, vmul(normal, vdot(normal, dst) * -2));
+
+	lamb_f = vdot(light_dir, normal);
+
+	if(lamb_f < 0 || TraceRay(intersection, light_dir, &t, &normal))
+		lamb_f = 0;
+
+	color = pow(vdot(light_dir, half_vec) * (lamb_f > 0), 99);
+
+	if((match & 1) != 0){
+		intersection = vmul(intersection, 0.2);
+		return ((int)(ceil(intersection.x) + ceil(intersection.y)) & 1) != 0? v(3,1,1): vmul(v(3,3,3), (lamb_f * 0.2 + 0.1));
+	}
+
+	return vadd(v(color,color,color), vmul(Sample(intersection, half_vec), 0.5));
+}
+
+void
+main()
+{
+	vec cam_forward, cam_up, cam_right, c, color, delta;
+	int x, y, r;
+
+	print("P6 512 512 255 ");
+
+	cam_forward = vnorm(v(-6,-16,0));
+	cam_up = vmul(vnorm(vcross(v(0,0,1), cam_forward)), 0.002);
+	cam_right = vmul(vnorm(vcross(cam_forward, cam_up)), 0.002);
+	c = vadd(vmul(vadd(cam_up, cam_right), -256), cam_forward);
+
+	for(y = 512; y--;)
+		for(x = 512; x--;){
+			color = v(13,13,13);
+			for(r = 64; r--;){
+				delta = vadd(vmul(vmul(cam_up, R() - 0.5), 99), vmul(vmul(cam_right, R() - 0.5), 99));
+				color = vadd(vmul(Sample(vadd(v(17,16,8), delta), vnorm(vmul(vadd(vmul(delta, -1), vadd(vadd(vmul(cam_up, R()+x), vmul(cam_right, R()+y)), c)), 16))), 3.5), color);
+			}
+			print("%c%c%c", (int)color.x, (int)color.y, (int)color.z);
+		}
+	exits(nil);
+}
diff --git a/mkfile b/mkfile
new file mode 100644
index 0000000..050189b
--- /dev/null
+++ b/mkfile
@@ -0,0 +1,8 @@
+</$objtype/mkfile
+
+BIN=/$objtype/bin
+TARG=bcardrt
+OFILES=\
+	bcardrt.$O\
+
+</sys/src/cmd/mkone
-- 
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