2 files changed, 70 insertions(+), 3 deletions(-)

M Makefile
M src/main.c

@@ 11,7 11,7 @@ bear:
 	bear -- make fclean all
 
 $(OUT): $(OBJ)
-	$(CC) -o $(OUT) $(OBJ)
+	$(CC) -o $(OUT) $(OBJ) -lm
 
 clean:
 	rm -f $(OBJ)

@@ 1,3 1,70 @@
+#include <stdio.h>
+
+// the mandelbrot set, basically, is a set of points on the complex plane -
+// those points are found using the following equation:
+//
+// z = z^2 + c
+//
+// c is an initial point on this complex plane. if the value of z is bigger than
+// 2 (which means that it's distance from the origin is larger than 2), it means
+// the value is out of the set.
+//
+// but what's going on with all the shapes and colors? this is a recursive
+// function.
+//
+// we start with z as 0, and then with the equation we get a new z, and then put
+// that new z onto the equation and we do that over and over. if z doesn't grow
+// over 2, then c is part of the set. if it does pass 2, we know for how many
+// iterations we have checked and we color based on that
+
+int mandelbrot_iterations(double cr, double ci, int max_iter) {
+    double zr = 0.0, zi = 0.0;
+    int iter = 0;
+    while (iter < max_iter) {
+        double zr2 = zr * zr;
+        double zi2 = zi * zi;
+        // avoids checking for sqrt
+        if (zr2 + zi2 > 4.0) {
+            break;
+        }
+        zi = 2.0 * zr * zi + ci;
+        zr = zr2 - zi2 + cr;
+        iter++;
+    }
+    return iter;
+}
+
+void get_color(int iter, int max_iter, int* r, int* g, int* b) {
+    if (iter == max_iter) {
+        *r = *g = *b = 0; // black inside the set
+        return;
+    }
+    double t = (double)iter / max_iter;
+    int gray = (int)((1.0 - t) * 255); // whiter the furthest it was
+    *r = *g = *b = gray;
+}
+
 int main() {
-    return -1;
-};
+    int width = 800;
+    int height = 600;
+    int max_iter = 100;
+
+    double x_min = -2.0, x_max = 1.0;
+    double y_min = -1.2, y_max = 1.2;
+
+    // PPM header (P3 = ASCII, width, height, max color value)
+    printf("P3\n%d %d\n255\n", width, height);
+
+    for (int py = 0; py < height; py++) {
+        for (int px = 0; px < width; px++) {
+            double cr = x_min + (x_max - x_min) * px / (width - 1);
+            double ci = y_min + (y_max - y_min) * py / (height - 1);
+            int iter = mandelbrot_iterations(cr, ci, max_iter);
+            int r, g, b;
+            get_color(iter, max_iter, &r, &g, &b);
+            printf("%d %d %d ", r, g, b);
+        }
+        printf("\n");
+    }
+    return 0;
+}