Slow ray caster (demo with cones)

#include <stdlib.h>
#include <math.h>
#include <stdio.h>
#include <SDL.h>

int bsize = 2;

int scw = 1280;
int sch = 1024;

int mapa = 32;
int mapb = 32;
int mapc = 32;

void filldata (int *hei, int *col)
{
    int idx;
    int x,y,z;
    for (y=0; y<mapb; y++)
    {
        for (x=0; x<mapa; x++)
        {
            int val;
            for (z=0; z<mapc; z++)
            {
                idx = y*mapa*mapb + x*mapa + z;
                double d = sqrt((x-10)*(x-10) + (y-10)*(y-10));
                int h = 30 - 3*d;
                if ((h>0)&&(z<h)) val = z;
                else val = -1;

                hei[idx] = val;
                col[idx] = 3*sqrt(x*x+y*y+z*z);
            }
        }
    }
}

void fillpalette (SDL_Surface *screen)
{
    SDL_Color colors[256];
    int i;
    /* Fill colors with color information */
    for(i=0;i<=256;i++)
    {
        colors[i].r=i;
        colors[i].g=i/3;
        colors[i].b=i/3;
    }
    SDL_SetPalette(screen, SDL_LOGPAL|SDL_PHYSPAL, colors, 0, 256);
}

void printdata (int *hei)
{
    int x,y,z;
    FILE *out = fopen ("testout.dat", "w");
    for (y=0; y<mapb; y++)
    {
        for (x=0; x<mapa; x++)
        {
            for (z=0; z<mapc; z++)
            {
                int idx = y*mapa*mapb + x*mapa + z;
                fprintf (out, "%i %i %i\n", x, y, hei[idx]);
            }
        }
    }
    fclose (out);
}

void blacken_screen (SDL_Surface *screen)
{
    SDL_Rect rect;
    rect.x = 0;
    rect.y = 0;
    rect.w = scw;
    rect.h = sch;

    SDL_FillRect (screen, &rect, 0);
}

void checkevents(double *ang, int *x, int *y, int *k)
{
    SDL_Event event;
    if (SDL_PollEvent(&event))
    {
        switch (event.type) {
        case SDL_QUIT:
            exit(0);
        }
    }
       Uint8 *keystate = SDL_GetKeyState (NULL);
    if (keystate[SDLK_LEFT]) *ang += 0.02;
    if (keystate[SDLK_RIGHT]) *ang -= 0.02;
    if (keystate[SDLK_UP]) *k -= 1;
    if (keystate[SDLK_DOWN]) *k += 1;
    if (keystate[SDLK_a] || keystate[SDLK_d] || keystate[SDLK_w] || keystate[SDLK_s])
    {
        int xd, yd;
        xd = 0;
        yd = 0;
        if (keystate[SDLK_a]) xd = -3;
        if (keystate[SDLK_d]) xd = 3;
        if (keystate[SDLK_w]) yd = 3;
        if (keystate[SDLK_s]) yd = -3;

        *x += yd*cos(*ang) + xd*sin(*ang);
        *y += -yd*sin(*ang) + xd*cos(*ang);
    }
}

int main ()
{
    int hei[mapa*mapb*mapc-1];
    int col[mapa*mapb*mapc-1];

    filldata (hei, col);
    printdata (hei);

    if ( SDL_Init(SDL_INIT_VIDEO) < 0 )
    {
        fprintf(stderr, "Cannot initialize SDL: %s\n", SDL_GetError());
        exit(1);
    }

    SDL_Surface *screen;
    screen = SDL_SetVideoMode(scw, sch, 8, SDL_SWSURFACE|SDL_HWPALETTE);
    if ( screen == NULL )
    {// Если установить разрешение не удалось
        fprintf(stderr, "Cannot set resolution %ix%i: %s\n", scw, sch, SDL_GetError());
        exit(1);
    }

    fillpalette (screen);

    int posx = 0;
    int posy = 0;
    int posz = 40;

    double ang = 0;
    int k = 1;

    double dd = 1;
    double de = dd * 128; // 128 is the max "distance"
    int x,y,z;

    double amax = M_PI/3.4; // FOV
    double a;

    int bin1 = mapb*mapb*mapb-mapa*mapa;
    int bin2 = mapa*mapa-mapa;
    int bin3 = mapc-1;

    int sx;

    while (1)
    {
        SDL_LockSurface(screen);

        blacken_screen (screen);

        double sinang = sin(ang);
        double cosang = cos(ang);

        for (sx=0;sx<scw;sx++)
        {
            double d;
            a = -amax + 2*amax*sx/scw;
            double tana = tan (a);
            for (d=de;d>=0;d-=dd)
            {
                double y1 = d*/*cos(amax)**/tana;
                double x1 = d;//*cos(amax);

                x = posx + x1*cosang+y1*sinang;
                y = posy - x1*sinang+y1*cosang;
                z = posz - k*d;//*sin(amax);

                x = abs(x);
                y = abs(y);

                int idx = ((y*mapa*mapb)&bin1) + ((x*mapa)&bin2);
                int zi;
                for (zi=0; zi<mapc; zi++)
                {
                    int idx2 = idx+zi;
                    int h = hei[idx2];
                    if (h==-1) break;

                    int sy = sch/2 + 150*(z-h)/(d+1);
                    int sy2 = sch/2 + 150*(z-h-bsize)/(d+1);

                    if (sy2<sch)
                    {
                        if (sy>=sch) sy = sch-1;
                        if (sy2<0) sy2 = 0;
                        int syi;
                        for (syi=sy; syi>=sy2; syi--)
                        {
                            *((Uint8*)screen->pixels+sx+scw*syi) = col[idx2];
                        }
                    }
                }
            }
        }

        SDL_UnlockSurface (screen);
        SDL_Flip (screen);
        checkevents(&ang, &posx, &posy, &k);
    }


    return atexit(SDL_Quit);
}