octree

commit 545ff5be825e3fa35ee502e9bc041bca47845825
parent 4f249861bda9257aae0b8568da0f352b4e28cab2
Author: glenda <glenda@9front.local>
Date:   Fri, 19 Mar 2021 13:08:57 +0000

render: implement ray marching

Diffstat:
M
render.c
 | 
81
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------------------

1 file changed, 63 insertions(+), 18 deletions(-)
diff --git a/render.c b/render.c
@@ -3,10 +3,12 @@
 
 #include "octree.h"
 
+#define SQR(X) (X * X)
+
 typedef struct Pixel Pixel;
 typedef struct Dot Dot;
-typedef struct Rad Rad;
 typedef struct Ray Ray;
+typedef struct Sphere Sphere;
 
 struct Pixel {
 	double r;
@@ -20,38 +22,80 @@ struct Dot {
 	double z;
 };
 
-struct Rad {
-	double u;
-	double v;
-	double z;
-};
 
 struct Ray {
 	Dot pos;
-	Rad dir;
+	Dot dir;
+};
+
+struct Sphere {
+	Dot pos;
+	double radius;
 };
 
 Pixel Pwhite = {1, 1, 1};
 Pixel Pblack = {0, 0, 0};
 
-Ray sphere = {{0.5, 0.5, 0}, {0, 0, 0.5}};
+Sphere sphere = {{0.5, 0.5, 0}, 0.5};
+
+double
+dotmod(Dot d)
+{
+	return sqrt(SQR(d.x) + SQR(d.y) + SQR(d.z));
+}
+
+Dot
+dotnorm(Dot d)
+{
+	double m;
+	m = dotmod(d);
+	return (Dot){d.x/m, d.y/m, d.z/m};
+}
+
+Dot
+dotxdot(Dot d1, Dot d2)
+{
+	return (Dot){d1.x * d2.x, d1.y * d2.y, d1.z * d2.z,};
+}
+
+Dot
+adddot(Dot d1, Dot d2)
+{
+	return (Dot){d1.x + d2.x, d1.y + d2.y, d1.z + d2.z,};
+}
+
+
+Dot
+subdot(Dot d1, Dot d2)
+{
+	return adddot(d1, (Dot){-d2.x, -d2.y, -d2.z});
+}
 
 int
-spherehit(Ray v, Ray s)
+spherehit(Ray *v, Sphere s)
 {
-	return (hypot(v.pos.x -s.pos.x, v.pos.y - s.pos.y) <= s.dir.z);
+	double d, old;
+	int i;
+	old = Inf(1);
+	for (i = 0; i < 1024; i++) {
+		d = dotmod(subdot(v->pos, s.pos)) - s.radius;
+		v->pos = adddot(v->pos,
+			dotxdot(dotnorm(v->dir), (Dot){d, d, d}));
+		if (d < 0.0001) {
+			return 1;
+		}
+		if (d > old) return 0;
+		old = d;
+	}
+	return 0;
 }
 
 Pixel
 ray(Ray v)
 {
-	Pixel p = {
-		.r = (v.pos.x + v.pos.y)/2,
-		.g = 0,
-		.b = 0,
-	};
-	if (spherehit(v, sphere)) {
-		p = Pblack;
+	Pixel p = Pblack;
+	if (spherehit(&v, sphere)) {
+		p = Pwhite;
 	}
 	return p;
 }
@@ -62,7 +106,8 @@ render(int x, int y)
 	Pixel p;
 	int r, g, b;
 	Ray v;
-	v.pos = (Dot){ (double)x/256.0, (double)y/256.0, 0 };
+	v.pos = (Dot){ (double)x/256.0, (double)y/256.0, -100 };
+	v.dir = (Dot){ 0, 0, 1 };
 	p = ray(v);
 	r = 0xff * p.r;
 	g = 0xff * p.g;