Create a gist now

Instantly share code, notes, and snippets.

What would you like to do?
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
typedef int i; //Save space by using 'i' instead of 'int'
typedef float f; //Save even more space by using 'f' instead of 'float'
//Define a vector class with constructor and operator: 'v'
struct v {
f x,y,z; // Vector has three float attributes.
v operator+(v r){return v(x+r.x,y+r.y,z+r.z);} //Vector add
v operator*(f r){return v(x*r,y*r,z*r);} //Vector scaling
f operator%(v r){return x*r.x+y*r.y+z*r.z;} //Vector dot product
v(){} //Empty constructor
v operator^(v r){return v(y*r.z-z*r.y,z*r.x-x*r.z,x*r.y-y*r.x);} //Cross-product
v(f a,f b,f c){x=a;y=b;z=c;} //Constructor
v operator!(){return *this*(1 /sqrt(*this%*this));} // Used later for normalizing the vector
i G[]={31768, 33316, 66114, 67138, 65572, 65560, 33792, 30720, 0};
// Random generator, return a float within range [0-1]
f R(){return(f)rand()/RAND_MAX;}
//The intersection test for line [o,v].
// Return 2 if a hit was found (and also return distance t and bouncing ray n).
// Return 0 if no hit was found but ray goes upward
// Return 1 if no hit was found but ray goes downward
i T(v o,v d,f& t,v& n) {
i m=0;
f p=-o.z/d.z;
//The world is encoded in G, with 9 lines and 19 columns
for(i k=19;k--;) //For each columns of objects
for(i j=9;j--;) //For each line on that columns
if(G[j]&1<<k) { //For this line j, is there a sphere at column i ?
// There is a sphere but does the ray hits it ?
v p=o+v(-k,3,-j-4);
f b=p%d,c=p%p-1,q=b*b-c;
// Does the ray hit the sphere ?
if(q>0) {
//It does, compute the distance camera-sphere
f s=-b-sqrt(q);
if(s<t && s>.01)
// So far this is the minimum distance, save it. And also
// compute the bouncing ray vector into 'n'
t=s, n=!(p+d*t), m=2;
return m;
// (S)ample the world and return the pixel color for
// a ray passing by point o (Origin) and d (Direction)
v S(v o,v d) {
f t;
v n;
//Search for an intersection ray Vs World.
i m=T(o,d,t,n);
if(!m) // m==0
//No sphere found and the ray goes upward: Generate a sky color
return v(.7,.6,1)*pow(1-d.z,4);
//A sphere was maybe hit.
v h=o+d*t, // h = intersection coordinate
l=!(v(9+R(),9+R(),16)+h*-1), // 'l' = direction to light (with random delta for soft-shadows).
r=d+n*(n%d*-2); // r = The half-vector
//Calculated the lambertian factor
f b=l%n;
//Calculate illumination factor (lambertian coefficient > 0 or in shadow)?
// Calculate the color 'p' with diffuse and specular component
f p=pow(l%r*(b>0),99);
if(m&1) { //m == 1
h=h*.2; //No sphere was hit and the ray was going downward: Generate a floor color
//m == 2 A sphere was hit. Cast an ray bouncing from the sphere surface.
return v(p,p,p)+S(h,r)*.5; //Attenuate color by 50% since it is bouncing (* .5)
// The main function. It generates a PPM image to stdout.
// Usage of the program is hence: ./card > erk.ppm
i main() {
printf("P6 512 512 255 "); // The PPM Header is issued
// The '!' are for normalizing each vectors with ! operator.
v g=!v(-5.5,-16,0), // Camera direction
a=!(v(0,0,1)^g)*.002, // Camera up vector...Seem Z is pointing up :/ WTF !
b=!(g^a)*.002, // The right vector, obtained via traditional cross-product
c=(a+b)*-256+g; // WTF ? See for more.
for(i y=512;y--;) //For each column
for(i x=512;x--;) { //For each pixel in a line
//Reuse the vector class to store not XYZ but a RGB pixel color
v p(13,13,13); // Default pixel color is almost pitch black
//Cast 64 rays per pixel (For blur (stochastic sampling) and soft-shadows.
for(i r=64;r--;) {
// The delta to apply to the origin of the view (For Depth of View blur).
v t=a*(R()-.5)*99+b*(R()-.5)*99; // A little bit of delta up/down and left/right
// Set the camera focal point v(17,16,8) and Cast the ray
// Accumulate the color returned in the p variable
p=S(v(17,16,8)+t, //Ray Origin
!(t*-1+(a*(R()+x)+b*(y+R())+c)*16) // Ray Direction with random deltas
// for stochastic sampling
)*3.5+p; // +p for color accumulation
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment