From 981b643df2def9846c112469e94644500015b8e6 Mon Sep 17 00:00:00 2001
From: rodri <rgl@antares-labs.eu>
Date: Tue, 27 Aug 2024 10:39:53 +0000
Subject: add a little procgen experiment.

---
 mkfile    |   1 +
 procgen.c | 196 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 197 insertions(+)
 create mode 100644 procgen.c

diff --git a/mkfile b/mkfile
index 2b6cf9c..d1b6997 100644
--- a/mkfile
+++ b/mkfile
@@ -6,6 +6,7 @@ TARG=\
 	med\
 	solar\
 	projtest\
+	procgen\
 
 OFILES=\
 	alloc.$O\
diff --git a/procgen.c b/procgen.c
new file mode 100644
index 0000000..7d48777
--- /dev/null
+++ b/procgen.c
@@ -0,0 +1,196 @@
+/*
+ * 	Greek Sunset
+ *
+ * based on Morgan McGuire's work:
+ * 	- https://casual-effects.com/research/McGuire2019ProcGen/McGuire2019ProcGen.pdf
+ * 	- https://www.shadertoy.com/view/WsdXWr
+ */
+#include <u.h>
+#include <libc.h>
+#include <thread.h>
+#include <draw.h>
+#include <memdraw.h>
+#include <mouse.h>
+#include <keyboard.h>
+#include <geometry.h>
+#include "libobj/obj.h"
+#include "libgraphics/graphics.h"
+#include "fns.h"
+
+#define min(a, b) ((a)<(b)?(a):(b))
+#define max(a, b) ((a)>(b)?(a):(b))
+
+Renderer *rctl;
+Camera *cam;
+Scene *scn;
+Entity *ent;
+Model *mdl;
+Primitive quad[2];
+
+static Color
+getskycolor(double x, double y)
+{
+	Color c;
+	double h;
+
+	h = max(0, 1.4 - y - pow(fabs(x - 0.5), 3));
+	c.r = pow(h, 3);
+	c.g = pow(h, 7);
+	c.b = 0.2 + pow(max(0, h - 0.1), 10);
+	c.a = 1;
+	return c;
+}
+
+static double
+fract(double x)
+{
+	double n;
+
+	return modf(x, &n);
+}
+
+static double
+hash(double x)
+{
+	return fract(sin(x) * 1e4);
+}
+
+static double
+noise(double x)
+{
+	double i, f, u;
+
+	i = floor(x);
+	f = fract(x);
+	u = f*f * (3 - 2*f);
+	return 2 * flerp(hash(i), hash(i + 1), u) - 1;
+}
+
+static double
+terrain(double x)
+{
+	double y, k;
+	int oct;
+
+	y = 0;
+	for(oct = 0; oct < 10; oct++){
+		k = 1<<oct;
+		y += noise(x*k)/k;
+	}
+	return y * 0.3 + 0.36;
+}
+
+static double
+water(double x, double dt)
+{
+	return (sin(71*x - 7*dt) * 0.5 + sin(200*x - 8*dt)) * 0.002 + 0.25;
+}
+
+static double
+tree(double x, double h)
+{
+	if(h < 0.5)
+		return 0;
+	else
+		return 0.2 * max(0, max(max(
+						fabs(sin(x * 109)),
+						fabs(sin(x * 150))), 
+						fabs(sin(x * 117))) +
+					noise(37 * x) +
+					noise(64 * x + 100) - 1.6);
+}
+
+static Point3
+vs(VSparams *sp)
+{
+	return vcs2clip(sp->su->camera, sp->v->p);
+}
+
+static Color
+fs(FSparams *sp)
+{
+	Point2 uv;
+	double dt, shift, h;
+
+	uv = Pt2(sp->p.x,sp->p.y,1);
+	uv.x /= Dx(sp->su->fb->r);
+	uv.y /= Dy(sp->su->fb->r);
+	uv.y = 1 - uv.y;		/* make [0 0] the bottom-left corner */
+
+	dt = sp->su->uni_time/1e9;
+	shift = 0.09*dt + 0.2;
+	uv.x += shift;
+
+	h = max(water(uv.x, dt), terrain(uv.x));
+	h += tree(uv.x, h);
+
+	if(uv.y < h)
+		return Pt3(0,0,0,1);
+	return srgb2linear(getskycolor(uv.x, uv.y));
+}
+
+Shadertab shaders = {
+	.vshader = vs,
+	.fshader = fs
+};
+
+void
+usage(void)
+{
+	fprint(2, "usage: %s [-s frames] [dx [dy]]\n", argv0);
+	exits("usage");
+}
+
+void
+threadmain(int argc, char *argv[])
+{
+	Memimage *out;
+	Point dim;
+	int skip;
+
+	dim = Pt(800,400);
+	skip = 0;
+	ARGBEGIN{
+	case 's': skip = strtoul(EARGF(usage()), nil, 10); break;
+	default: usage();
+	}ARGEND;
+	if(argc > 0)
+		switch(argc){
+		case 1: dim.x = dim.y = strtoul(argv[0], nil, 10); break;
+		case 2:
+			dim.x = strtoul(argv[0], nil, 10);
+			dim.y = strtoul(argv[1], nil, 10);
+			break;
+		default: usage();
+		}
+
+	if(memimageinit() != 0)
+		sysfatal("memimageinit: %r");
+	if((rctl = initgraphics()) == nil)
+		sysfatal("initgraphics: %r");
+
+	scn = newscene(nil);
+	mdl = newmodel();
+	ent = newentity(nil, mdl);
+
+	out = eallocmemimage(Rect(0,0,dim.x,dim.y), XRGB32);
+	cam = Cam(out->r, rctl, ORTHOGRAPHIC, 40*DEG, 1, 10);
+	placecamera(cam, scn, Pt3(0,0,0,1), Vec3(0,0,-1), Vec3(0,1,0));
+
+	quad[0].type = quad[1].type = PTriangle;
+	quad[0].v[0].p = viewport2vcs(cam, Pt3(out->r.min.x, out->r.max.y, 1, 1));
+	quad[0].v[1].p = viewport2vcs(cam, Pt3(out->r.max.x, out->r.min.y, 1, 1));
+	quad[0].v[2].p = viewport2vcs(cam, Pt3(out->r.min.x, out->r.min.y, 1, 1));
+	quad[1].v[0].p = quad[0].v[0].p;
+	quad[1].v[1].p = viewport2vcs(cam, Pt3(out->r.max.x, out->r.max.y, 1, 1));
+	quad[1].v[2].p = quad[0].v[1].p;
+	mdl->addprim(mdl, quad[0]);
+	mdl->addprim(mdl, quad[1]);
+	scn->addent(scn, ent);
+
+	do shootcamera(cam, &shaders); while(skip--);
+	cam->view->memdraw(cam->view, out);
+	writememimage(1, out);
+
+	threadexitsall(nil);
+}
-- 
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