How to understand this RayTracer code [closed] - c++

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So this RT code creates a 3D image, with blur, through raw code. How is that actually done without any modelling tools?
I am currently working to understand how RT work and different ways to implement them, so this was kind of cool to see such a small amount of code producing a pretty impressive 3D image.
#include <stdlib.h> // card > aek.ppm
#include <stdio.h>
#include <math.h>
#include <fstream>
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()
{
FILE * pFile;
pFile = fopen("d:\\myfile3.ppm", "w");
fprintf(pFile,"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;
}
fprintf(pFile, "%c%c%c", (i)p.x, (i)p.y, (i)p.z);
}
}

Answer 1

My dear friend that's Paul Heckbert code's right?
You could at least mention it.
For people thinking this code is unreadable, here is why:
This guy made a code that could fit on a credit card, that was the goal :)
His website: http://www.cs.cmu.edu/~ph/
Edit: Knowing the source of this code may help you understand it. Even if it'snot your main motivation...
If you are really interested in raytracing, start with other sources.
Take a look at this website http://www.scratchapixel.com/lessons/3d-basic-lessons/lesson-1-writing-a-simple-raytracer/source-code/ (Plus it talk about your code)

Answer 2

This code is not really special. It is basically a ray tracer that was obfuscated into a form that makes it fit on a business card (see https://www.cs.cmu.edu/~ph/).
How is that actually done without any modelling tools?
You don't need tools to render anything. You could even create a complete game of WoW (or what's hip at the moment) without any modelling tool. Modelling tools just make your live easier w.r.t. certain kinds of scenes (read: very complex ones).
You could always hardcode these data, or hack them manually into some external file.
You could also use parametric generators; Perlin Noise is one of the more popular examples thereof.
In a ray tracer, it happens that it is very simple to start out without modelling tools, as it is very simple to calculate geometric intersections between the rendering primitive "ray" and any finite geometric primitive. E.g., intersection a non-approximated, "perfect" sphere is just a few lines of code.
tl;dr: Data is just data. How you create and crunch it is completely up to you.