Andrew Kensler's business card raytracer.

businesscard_raytracer.c

#include <stdlib.h>   // card > aek.ppm
#include <stdio.h>
#include <math.h>
typedef int i;typedef float f;struct v{
f x,y,z;v operator+(v r){return v(x+r.x
,y+r.y,z+r.z);}v operator*(f r){return
v(x*r,y*r,z*r);}f operator%(v r){return
x*r.x+y*r.y+z*r.z;}v(){}v operator^(v r
){return v(y*r.z-z*r.y,z*r.x-x*r.z,x*r.
y-y*r.x);}v(f a,f b,f c){x=a;y=b;z=c;}v
operator!(){return*this*(1/sqrt(*this%*
this));}};i G[]={247570,280596,280600,
249748,18578,18577,231184,16,16};f R(){
return(f)rand()/RAND_MAX;}i T(v o,v d,f
&t,v&n){t=1e9;i m=0;f p=-o.z/d.z;if(.01
<p)t=p,n=v(0,0,1),m=1;for(i k=19;k--;)
for(i j=9;j--;)if(G[j]&1<<k){v p=o+v(-k
,0,-j-4);f b=p%d,c=p%p-1,q=b*b-c;if(q>0
){f s=-b-sqrt(q);if(s<t&&s>.01)t=s,n=!(
p+d*t),m=2;}}return m;}v S(v o,v d){f t
;v n;i m=T(o,d,t,n);if(!m)return v(.7,
.6,1)*pow(1-d.z,4);v h=o+d*t,l=!(v(9+R(
),9+R(),16)+h*-1),r=d+n*(n%d*-2);f b=l%
n;if(b<0||T(h,l,t,n))b=0;f p=pow(l%r*(b
>0),99);if(m&1){h=h*.2;return((i)(ceil(
h.x)+ceil(h.y))&1?v(3,1,1):v(3,3,3))*(b
*.2+.1);}return v(p,p,p)+S(h,r)*.5;}i
main(){printf("P6 512 512 255 ");v g=!v
(-6,-16,0),a=!(v(0,0,1)^g)*.002,b=!(g^a
)*.002,c=(a+b)*-256+g;for(i y=512;y--;)
for(i x=512;x--;){v p(13,13,13);for(i r
=64;r--;){v t=a*(R()-.5)*99+b*(R()-.5)*
99;p=S(v(17,16,8)+t,!(t*-1+(a*(R()+x)+b
*(y+R())+c)*16))*3.5+p;}printf("%c%c%c"
,(i)p.x,(i)p.y,(i)p.z);}}

businesscard_raytracer_formatted.c

#include <stdlib.h>   // card > aek.ppm
#include <stdio.h>
#include <math.h>

typedef int i;
typedef float f;

struct v
{
    f x,y,z;

    v operator+(v r)
    {
        return v(x+r.x,y+r.y,z+r.z);
    }

    v operator*(f r)
    {
        return v(x*r,y*r,z*r);
    }

    f operator%(v r)
    {
        return x*r.x+y*r.y+z*r.z;
    }

    v()
    {
    }

    v operator^(v r)
    {
        return v(y*r.z-z*r.y,z*r.x-x*r.z,x*r.y-y*r.x);
    }

    v(f a,f b,f c)
    {
        x=a;y=b;z=c;
    }

    v operator!()
    {
        return *this*(1/sqrt(*this%*this));
    }
};

i G[]={247570,280596,280600,249748,18578,18577,231184,16,16};

f R()
{
    return(f)rand()/RAND_MAX;
}

i T(v o,v d,f&t,v&n)
{
    t=1e9;
    i m=0;
    f p=-o.z/d.z;

    if(.01<p)
    {
        t=p,n=v(0,0,1),m=1;
    }

    for(i k=19;k--;)
    {
        for(i j=9;j--;)
        {
            if(G[j]&1<<k)
            {
                v p=o+v(-k,0,-j-4);
                f b=p%d,c=p%p-1,q=b*b-c;

                if(q>0)
                {
                    f s=-b-sqrt(q);
                    
                    if(s<t&&s>.01)
                    {
                        t=s,n=!(p+d*t),m=2;
                    }
                }
            }
        }
    }

    return m;
}

v S(v o,v d)
{
    f t;
    v n;
    i m=T(o,d,t,n);

    if(!m)
    {
        return v(.7,.6,1)*pow(1-d.z,4);
    }

    v h=o+d*t,l=!(v(9+R(),9+R(),16)+h*-1),r=d+n*(n%d*-2);
    f b=l%n;

    if(b<0||T(h,l,t,n))
    {
        b=0;
    }

    f p=pow(l%r*(b>0),99);

    if(m&1)
    {
        h=h*.2;
        return((i)(ceil(h.x)+ceil(h.y))&1?v(3,1,1):v(3,3,3))*(b*.2+.1);
    }

    return v(p,p,p)+S(h,r)*.5;
}

i main()
{
    printf("P6 512 512 255 ");
    v g=!v(-6,-16,0),a=!(v(0,0,1)^g)*.002,b=!(g^a)*.002,c=(a+b)*-256+g;

    for(i y=512;y--;)
    {
        for(i x=512;x--;)
        {
            v p(13,13,13);

            for(i r=64;r--;)
            {
                v t=a*(R()-.5)*99+b*(R()-.5)*99;
                p=S(v(17,16,8)+t,!(t*-1+(a*(R()+x)+b*(y+R())+c)*16))*3.5+p;
            }

            printf("%c%c%c",(i)p.x,(i)p.y,(i)p.z);
        }
    }
}

This is not Paul Heckbert's business card raytracer. It is Andrew Kensler's business card raytracer. (Note "aek.ppm" in the first line.)

ty 👍