void intensifyPixel(int x, int y, double distance, unsigned long *grid[framebufferheight][framebufferwidth], unsigned long color){
    unsigned long intensity;
    //assign intensity returned from filter function
    intensity = filter ((floor(fabs (distance)) + .5), color);
    //write intensity value to x,y coordinates of framebuffer memory
    *( *(grid + y) + x) = intensity;
}

void intensifyPixel(int x, int y, double distance, unsigned short *grid[framebufferheight][framebufferwidth], unsigned short color){
    unsigned short intensity;
    //assign intensity returned from filter function
    intensity = filter ((floor(fabs (distance)) + .5), color);
    //write intensity value to x,y coordinates of framebuffer memory
    *( *(grid + y) + x) = intensity;
}

unsigned long grid[framebufferheight][framebufferwidth]

unsigned long (*grid)[framebufferwidth]

// 2-d array of unsigned longs
unsigned long grid[framebufferheight][framebufferwidth];

// pointer to an array of framebufferwidth unsigned longs
unsigned long (*grid)[framebufferwidth] = malloc(sizeof(unsigned long) * framebufferheight * framebufferwidth);

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

#define framebufferheight 20
#define framebufferwidth  64

void visualize(unsigned long (*grid)[framebufferwidth])
{
  int y, x;
  for (y = 0; y < framebufferheight; y++)
  {
    for (x = 0; x < framebufferwidth; x++)
      printf("%c", (char)grid[y][x]);
    printf("n");
  }
}

void drawBox(unsigned long (*grid)[framebufferwidth],
             int x1, int y1, int x2, int y2, char c)
{
  int y, x;
  for (y = y1; y <= y2 ; y++)
    for (x = x1; x <= x2; x++)
      grid[y][x] = c;
}

void clear(unsigned long (*grid)[framebufferwidth], char c)
{
  drawBox(grid, 0, 0, framebufferwidth - 1, framebufferheight - 1, c);
}

int main(void)
{
  {
    unsigned long (*grid)[framebufferwidth] = malloc(sizeof(unsigned long) * framebufferheight * framebufferwidth);
    clear(grid, '.');
    drawBox(grid, 1, 1, 10, 5, '1');
    drawBox(grid, 40, 10, 55, 18, '2');
    grid[framebufferheight / 2][framebufferwidth / 2] = '+';
    visualize(grid);
  }

  {
    unsigned long grid[framebufferheight][framebufferwidth];
    clear(grid, ',');
    drawBox(grid, 1, 1, 10, 5, 'a');
    drawBox(grid, 40, 10, 55, 18, 'b');
    grid[framebufferheight / 2][framebufferwidth / 2] = '*';
    visualize(grid);
  }

  return 0;
}

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