fractal effect is cooking

[dosdemo] / src / gfxutil.c

diff --git a/src/gfxutil.c b/src/gfxutil.c
new file mode 100644 (file)
index 0000000..0257f79
--- /dev/null
+++ b/src/gfxutil.c
@@ -0,0 +1,144 @@
+#include "gfxutil.h"
+#include "demo.h"
+
+enum {
+       IN              = 0,
+       LEFT    = 1,
+       RIGHT   = 2,
+       TOP             = 4,
+       BOTTOM  = 8
+};
+
+static int outcode(int x, int y, int xmin, int ymin, int xmax, int ymax)
+{
+       int code = 0;
+
+       if(x < xmin) {
+               code |= LEFT;
+       } else if(x > xmax) {
+               code |= RIGHT;
+       }
+       if(y < ymin) {
+               code |= TOP;
+       } else if(y > ymax) {
+               code |= BOTTOM;
+       }
+       return code;
+}
+
+#define FIXMUL(a, b)   (((a) * (b)) >> 8)
+#define FIXDIV(a, b)   (((a) << 8) / (b))
+
+#define LERP(a, b, t)  ((a) + FIXMUL((b) - (a), (t)))
+
+int clip_line(int *x0, int *y0, int *x1, int *y1, int xmin, int ymin, int xmax, int ymax)
+{
+       int oc_out;
+
+       int oc0 = outcode(*x0, *y0, xmin, ymin, xmax, ymax);
+       int oc1 = outcode(*x1, *y1, xmin, ymin, xmax, ymax);
+
+       long fx0, fy0, fx1, fy1, fxmin, fymin, fxmax, fymax;
+
+       if(!(oc0 | oc1)) return 1;      /* both points are inside */
+
+       fx0 = *x0 << 8;
+       fy0 = *y0 << 8;
+       fx1 = *x1 << 8;
+       fy1 = *y1 << 8;
+       fxmin = xmin << 8;
+       fymin = ymin << 8;
+       fxmax = xmax << 8;
+       fymax = ymax << 8;
+
+       for(;;) {
+               long x, y, t;
+
+               if(oc0 & oc1) return 0;         /* both have points with the same outbit, not visible */
+               if(!(oc0 | oc1)) break;         /* both points are inside */
+
+               oc_out = oc0 ? oc0 : oc1;
+
+               if(oc_out & TOP) {
+                       t = FIXDIV(fymin - fy0, fy1 - fy0);
+                       x = LERP(fx0, fx1, t);
+                       y = fymin;
+               } else if(oc_out & BOTTOM) {
+                       t = FIXDIV(fymax - fy0, fy1 - fy0);
+                       x = LERP(fx0, fx1, t);
+                       y = fymax;
+               } else if(oc_out & LEFT) {
+                       t = FIXDIV(fxmin - fx0, fx1 - fx0);
+                       x = fxmin;
+                       y = LERP(fy0, fy1, t);
+               } else if(oc_out & RIGHT) {
+                       t = FIXDIV(fxmax - fx0, fx1 - fx0);
+                       x = fxmax;
+                       y = LERP(fy0, fy1, t);
+               }
+
+               if(oc_out == oc0) {
+                       fx0 = x;
+                       fy0 = y;
+                       oc0 = outcode(fx0 >> 8, fy0 >> 8, xmin, ymin, xmax, ymax);
+               } else {
+                       fx1 = x;
+                       fy1 = y;
+                       oc1 = outcode(fx1 >> 8, fy1 >> 8, xmin, ymin, xmax, ymax);
+               }
+       }
+
+       *x0 = fx0 >> 8;
+       *y0 = fy0 >> 8;
+       *x1 = fx1 >> 8;
+       *y1 = fy1 >> 8;
+       return 1;
+}
+
+void draw_line(int x0, int y0, int x1, int y1, unsigned short color)
+{
+       int i, dx, dy, x_inc, y_inc, error;
+       unsigned short *fb = fb_pixels;
+
+       fb += y0 * fb_width + x0;
+
+       dx = x1 - x0;
+       dy = y1 - y0;
+
+       if(dx >= 0) {
+               x_inc = 1;
+       } else {
+               x_inc = -1;
+               dx = -dx;
+       }
+       if(dy >= 0) {
+               y_inc = fb_width;
+       } else {
+               y_inc = -fb_width;
+               dy = -dy;
+       }
+
+       if(dx > dy) {
+               error = dy * 2 - dx;
+               for(i=0; i<=dx; i++) {
+                       *fb = color;
+                       if(error >= 0) {
+                               error -= dx * 2;
+                               fb += y_inc;
+                       }
+                       error += dy * 2;
+                       fb += x_inc;
+               }
+       } else {
+               error = dx * 2 - dy;
+               for(i=0; i<=dy; i++) {
+                       *fb = color;
+                       if(error >= 0) {
+                               error -= dy * 2;
+                               fb += x_inc;
+                       }
+                       error += dx * 2;
+                       fb += y_inc;
+               }
+       }
+}