C++ raytracer ppm says not enough data to display the image - c++

Question

Making a ray tracer and the code was failing so I decided to redo the whole thing and change the logic of the object but now for some reason, it keeps giving me an error and I've already tried editing it multiple times. ImageMagick give me an error saying that there isn't enough data to produce the ppm
other than the bit about the object the main logic how the ppm is produced hasn't changed much so I can't really figure out where the error is.
main.cpp
vec color(const ray& r, float t, vec a, vec centre)
{
vector <Light> lighting;
lighting.push_back(Light(vec(0, 0, 50), vec(0, 0, -1)));
vec totalLight{0, 0, 0};
for(int i = 0; i <lighting.size(); i++){
if(t > 0.0){
vec hit = unit_vector(r.p_at_par(t) - centre);
vec L = unit_vector(lighting[i].position() - r.p_at_par(t));
vec R = L - 2.0*dot(L, hit)*hit;
vec S = vec(1, 1, 1)*pow(max(0.f, dot(R, vec(0, 0, -1))), 50);//Specular component
vec D = (a * max(0.f, dot(L, hit)) * 1.0);//Diffuse component
totalLight += S + D;
return totalLight;
}
}
}
float clamp(float a)
{
return (a > 255)? 255: (a < 0)? 0: a;
}
int main()
{
const int w = 200, h = 100;
FILE *fp;
fp = fopen("img.ppm", "wb");
fprintf(fp, "P6\n%d %d\n255\n", w, h);
vec lower_corner(-2.0, -1.0, -1.0);
vec horizontal(4.0, 0.0, 0.0);
vec vertical(0.0, 2.0, 0.0);
vec origin(0.0, 0.0, 0.0);
vector <sphere> objects;
objects.push_back(sphere(vec(0,-100.5,-1), 100, vec(0, 1, 0)));
objects.push_back(sphere(vec(0, 0, -1), 0.5, vec(1, 0, 0)));
objects.push_back(sphere(vec(5, 5,-2), 3, vec(1, 0, 0)));
for(int j = h - 1; j >= 0; j--)
{
for(int i = 0; i < w; i++)
{
vec col(0, 0, 0);
static unsigned char pixel[3];
sphere* ClosestObject = NULL;
float u = float(i + random_double())/float(w);
float v = float(j + random_double())/float(h);
ray r(origin, lower_corner + u*horizontal + v*vertical);
float t = 0.0;
float t_near = 200000.0;
vec pixelColor(0.52 , 0.52 ,0.48);
for(int j = 0; j < objects.size(); j++)
{
if(t = objects[j].intersect(r))
{
if(t < t_near)
{
ClosestObject = &objects[j];
t_near = t;
}
}
if( t = 200000.0)
col = pixelColor;
else
col = color(r, t, ClosestObject->color, ClosestObject->centre);
pixel[0] = int(clamp(col.r() * 255));
pixel[1] = int(clamp(col.g() * 255));
pixel[2] = int(clamp(col.b() * 255));
fwrite(pixel, 3, 1, fp);
}
}
fclose(fp);
return 0;
}
}

Answer 1

Actually, a comment but too much text for that…
Your indentation is broken.
Hence, you didn't notice that the return 0; appears in the outer for loop, this one:
for(int j = h - 1; j >= 0; j--)
{
ends with:
fclose(fp);
return 0;
}
Additionally, the
fwrite(pixel, 3, 1, fp);
appears in the most inner loop
for (int j = 0; j < objects.size(); j++)
which is IMHO wrong as well.
So, the produced .ppm file claims to have w×h pixels but instead it provides w×objects.size() pixels.
If objects.size() < h (what I would expect) then you will have too less pixels in the .ppm file and ImageMagick will notice and complain.
Your source code, auto-formatted in my VS2017:
int main()
{
const int w = 200, h = 100;
FILE *fp;
fp = fopen("img.ppm", "wb");
fprintf(fp, "P6\n%d %d\n255\n", w, h);
vec lower_corner(-2.0, -1.0, -1.0);
vec horizontal(4.0, 0.0, 0.0);
vec vertical(0.0, 2.0, 0.0);
vec origin(0.0, 0.0, 0.0);
vector <sphere> objects;
objects.push_back(sphere(vec(0, -100.5, -1), 100, vec(0, 1, 0)));
objects.push_back(sphere(vec(0, 0, -1), 0.5, vec(1, 0, 0)));
objects.push_back(sphere(vec(5, 5, -2), 3, vec(1, 0, 0)));
for (int j = h - 1; j >= 0; j--)
{
for (int i = 0; i < w; i++)
{
vec col(0, 0, 0);
static unsigned char pixel[3];
sphere* ClosestObject = NULL;
float u = float(i + random_double()) / float(w);
float v = float(j + random_double()) / float(h);
ray r(origin, lower_corner + u * horizontal + v * vertical);
float t = 0.0;
float t_near = 200000.0;
vec pixelColor(0.52, 0.52, 0.48);
for (int j = 0; j < objects.size(); j++)
{
if (t = objects[j].intersect(r))
{
if (t < t_near)
{
ClosestObject = &objects[j];
t_near = t;
}
}
if (t = 200000.0)
col = pixelColor;
else
col = color(r, t, ClosestObject->color, ClosestObject->centre);
pixel[0] = int(clamp(col.r() * 255));
pixel[1] = int(clamp(col.g() * 255));
pixel[2] = int(clamp(col.b() * 255));
fwrite(pixel, 3, 1, fp);
}
}
fclose(fp);
return 0;
}
}
Please, check indentation and place closing curly-brackets correctly. Then it should work as before…