1 files changed, 199 insertions, 0 deletions
diff --git a/demos/raytrace.cpp b/demos/raytrace.cpp
new file mode 100644
index 00000000..d51bc45e
--- /dev/null
+++ b/demos/raytrace.cpp
@@ -0,0 +1,199 @@
+// sphere flake bvh raytracer (c) 2005, thierry berger-perrin <tbptbp@gmail.com>
+// this code is released under the GNU Public License.
+// Emscripten changes: stdlib.h, some printf stuff, SIZE, SDL
+//                                                        XXX - new in this file
+
+#include <cmath>       // see http://ompf.org/ray/sphereflake/
+#include <iostream>    // compile with ie g++ -O2 -ffast-math sphereflake.cc
+#include <stdlib.h>
+
+#include "SDL/SDL.h"
+#include "emscripten.h"
+
+#define GIMME_SHADOWS  // usage: ./sphereflake [lvl=6] >pix.ppm
+
+SDL_Surface* screen = NULL;
+
+enum { childs = 9, ss= 2, ss_sqr = ss*ss }; /* not really tweakable anymore */
+static const double infinity = 1./0, epsilon = 1e-12;
+
+struct v_t{ double x,y,z;v_t(){}
+	v_t(const double a,const double b,const double c):x(a),y(b),z(c){}
+	v_t operator+(const v_t&v)const{return v_t(x+v.x,y+v.y,z+v.z);}
+	v_t operator-(const v_t&v)const{return v_t(x-v.x,y-v.y,z-v.z);}
+	v_t operator-()const{return v_t(-x,-y,-z);}
+	v_t operator*(const double d)const{return v_t(x*d,y*d,z*d);}
+	v_t cross(const v_t&v)const{return v_t(y*v.z-z*v.y,z*v.x-x*v.z,x*v.y-y*v.x);}
+	v_t norm()const{return*this*(1./sqrt(magsqr()));}
+	double dot(const v_t&v)const{return x*v.x+y*v.y+z*v.z;}
+	double magsqr()const{return dot(*this);}
+};
+
+//static const v_t light(v_t(0.5,-.95,1.775).norm()); /*pick one*/
+static const v_t light(v_t(-0.5,-.65,.9).norm()); /*fiat lux*/
+
+struct ray_t{
+	v_t o,d;
+	ray_t(const v_t&v):o(v){}
+	 ray_t(const v_t&v,const v_t&w):o(v),d(w){}
+};
+struct hit_t {
+	v_t n;
+	double t;
+	hit_t():n(v_t(0,0,0)),t(infinity){}
+};
+
+struct sphere_t{ 
+	v_t o;
+	double r;
+	sphere_t(){}
+	sphere_t(const v_t&v,double d):o(v),r(d){}
+	v_t get_normal(const v_t&v)const{return(v-o)*(1./r);}
+	double intersect(const ray_t&ray)const{
+		const v_t v(o-ray.o); const double b=ray.d.dot(v),disc=b*b-v.magsqr()+r*r;
+		if(disc < 0.)
+			return infinity; /*branch away from the square root*/
+		const double d=sqrt(disc), t2=b+d, t1=b-d; /*cond. move*/
+		if(t2 < 0.)
+			return infinity;
+		else
+			return(t1 > 0.? t1 : t2);
+	}
+};
+
+struct node_t; 
+static node_t *pool=0, *end=0;
+
+struct node_t { /*a bvh in array form+skip for navigation.*/
+	sphere_t bound,leaf;
+	long diff;/*far from optimal*/
+	node_t(){} node_t(const sphere_t&b,const sphere_t&l,const long jump) :bound(b),leaf(l),diff(jump){}
+	template<bool shadow> static void intersect(const ray_t &ray,hit_t &hit){
+		const node_t*p=pool;
+		while(p < end) {
+			if(p->bound.intersect(ray)>=hit.t) /*missed bound*/
+				p+=p->diff; /*skip subtree*/
+			else{
+				const double t=p->leaf.intersect(ray);
+				if(t < hit.t) { /*if hit, update, then break for shadows*/
+					 hit.t=t;
+					if(shadow) break;
+					hit.n=p->leaf.get_normal(ray.o+ray.d*t);
+				}
+				++p; /*next!*/
+			}
+		}
+	}
+};
+
+static double ray_trace(const node_t*const scene,const ray_t&ray) {
+	hit_t hit;
+	scene->intersect<false>(ray,hit);// trace primary
+	const double diffuse = hit.t==infinity ? 0. : -hit.n.dot(light);
+	#ifdef GIMME_SHADOWS
+		if (diffuse <= 0.)
+			return 0.;
+		const ray_t sray(ray.o+(ray.d*hit.t)+(hit.n*epsilon),-light);
+		hit_t shit;
+		scene->intersect<true>(sray,shit);// trace shadow
+		return shit.t==infinity ? diffuse : 0.;
+	#else
+		return diffuse > 0. ? diffuse : 0.;
+	#endif
+}
+
+static const double grid[ss_sqr][2]={ /*our rotated grid*/
+	{-3/3.,-1/3.},{+1/3.,-3/3.},
+	{-1/3.,+3/3.},{+3/3.,+1/3.}
+};
+static void trace_line(const int width,const int height, const int y) {
+	const double w=width,h=height,rcp=1/double(ss),scale=256./double(ss_sqr);
+	ray_t ray(v_t(0,0,-4.5)); /* eye, looking into Z */
+	v_t rgss[ss_sqr];
+	for(int i=0;i<ss_sqr;++i) /*precomp.*/ {
+		rgss[i]=v_t(grid[i][0]*rcp-w/2.,grid[i][1]*rcp-h/2.,0);
+	}
+	v_t scan(0,y,std::max(w,h)); /*scan line*/
+  SDL_LockSurface(screen);
+
+	for(int j=width;j;--j) {
+		double g=0;
+		for(int idx=0;idx < ss_sqr;++idx){ /*AA*/
+			ray.d=(scan+rgss[idx]).norm();
+			g+=ray_trace(pool,ray); /*trace*/
+		}
+
+    for (int k = 0; k < 3; k++)
+      *((char*)screen->pixels + int((width - scan.y)*width*4 + scan.x*4) + k) = int(scale*g);
+
+		scan.x+=1; /*next pixel*/
+	}
+
+  SDL_UnlockSurface(screen);
+  SDL_Flip(screen); 
+}
+	
+struct basis_t{ /* bogus and compact, exactly what we need */
+	v_t up,b1,b2;
+	basis_t(const v_t&v){ const v_t n(v.norm());
+		if ((n.x*n.x !=1.)&(n.y*n.y !=1.)&(n.z*n.z !=1.)) {/*cough*/
+			b1=n;
+			if(n.y*n.y>n.x*n.x) {
+				if(n.y*n.y>n.z*n.z)
+					b1.y=-b1.y;
+				else b1.z=-b1.z;
+			}
+			else if(n.z*n.z > n.x*n.x)
+				b1.z=-b1.z;
+			else b1.x=-b1.x;
+		}
+		else
+			b1=v_t(n.z,n.x,n.y);/*leaves some cases out,dodge them*/
+		
+		up=n;
+		b2=up.cross(b1);
+		b1=up.cross(b2);
+	}
+};
+
+static node_t *create(node_t*n,const int lvl,int dist,v_t c,v_t d,double r) {
+	n = 1 + new (n) node_t(sphere_t(c,2.*r),sphere_t(c,r), lvl > 1 ? dist : 1);
+	if (lvl <= 1)
+		return n; /*if not at the bottom, recurse a bit more*/
+	dist=std::max((dist-childs)/childs,1); const basis_t b(d); 
+	const double nr=r*1/3.,daL=2.*M_PI/6.,daU=2.*M_PI/3.; double a=0;
+	for(int i=0;i<6;++i){ /*lower ring*/
+		const v_t ndir((d*-.2+b.b1*sin(a)+b.b2*cos(a)).norm()); /*transcendentals?!*/
+		n=create(n,lvl-1,dist,c+ndir*(r+nr),ndir,nr);
+		a+=daL;
+	}
+	a-=daL/3.;/*tweak*/
+	for(int i=0;i<3;++i){ /*upper ring*/
+		const v_t ndir((d*+.6+b.b1*sin(a)+b.b2*cos(a)).norm());
+		n=create(n,lvl-1,dist,c+ndir*(r+nr),ndir,nr); a+=daU;
+	}
+	return n;
+}
+
+#define SIZE 512
+int main(int argc,char*argv[]){
+	enum{ w = SIZE, h = w }; /* resolution */
+	const int lvl=(argc==2?std::max(atoi(argv[1]),2):6);
+	int count=childs, dec=lvl;
+	while(--dec > 1) count=(count*childs)+childs;
+	++count;
+	pool=new node_t[count];  /* raw */
+	end=pool+count;
+	create(pool,lvl,count,v_t(0,0,0),v_t(+.25,+1,-.5).norm(),1.); /* cooked */
+
+  SDL_Init(SDL_INIT_VIDEO);
+  screen = SDL_SetVideoMode(SIZE, SIZE, 32, SDL_SWSURFACE);
+  for (int y = h-1; y >= 0; y--)
+  	trace_line(w, h, y); /* served */
+
+  SDL_Delay( 20000 );
+  SDL_Quit();
+
+	return 0;
+}
+