Use two faces and show how they overlap (in progress)

- solidify/face.h (face_z0): calculate height of z0 plane
- solidify/level.c (draw_image): use face_z0 instead of open-coding the
  calculation
- solidify/overlap.c (draw_image, point): moved per-point processing from
  draw_image() to point()
- solidify/overlap.c (point): show differences between both faces
- solidify/solidify.c (usage, main): load both faces
- solidify/solidify.c (usage, main): accept distance between faces as third
  argument

solidify/face.h

@@ -38,6 +38,12 @@ struct face {
 };
 
 
+static inline double face_z0(const struct face *f, int x, int y)
+{
+	return f->z_ref+f->fx*(x-f->sx/2)+f->fy*(y-f->sy/2);
+}
+
+
 struct face *read_face(const char *name);
 
 #endif /* FACE_H */

solidify/level.c

@@ -42,7 +42,7 @@ static void draw_image(GtkWidget *widget, struct face *f)
 				p += 3;
 				continue;
 			}
-			z0 = f->z_ref+f->fx*(x-f->sx/2)+f->fy*(y-f->sy/2);
+			z0 = face_z0(f, x, y);
 			if (fabs(z-z0) < NEAR) {
 				*p++ = 255*fabs(z-z0);
 				*p++ = 255*fabs(z-z0);

solidify/overlap.c

@@ -73,12 +73,73 @@ static double zmix(struct face *f, double x, double y)
 }
 
 
+static void point(const struct solid *s, int x, int y, guchar *p)
+{
+	double za, zb, z;
+	int xa = x+s->a->a->min_x;
+	int ya = y+s->a->a->min_y;
+	int yb = sy(s)-1-y+s->a->a->min_y;
+
+	za = zmix(s->a,
+	    xa*s->a->m.a[0][0]+ya*s->a->m.a[0][1]+s->a->m.b[0],
+	    xa*s->a->m.a[1][0]+ya*s->a->m.a[1][1]+s->a->m.b[1]);
+
+	zb = zmix(s->b,
+	    xa*s->b->m.a[0][0]+yb*s->b->m.a[0][1]+s->b->m.b[0],
+	    xa*s->b->m.a[1][0]+yb*s->b->m.a[1][1]+s->b->m.b[1]);
+
+	if (za == UNDEF_F && zb == UNDEF_F)
+		return;
+
+	if (za == UNDEF_F) {
+		z = 128.0*(zb-s->b->a->min_z)/(s->b->a->max_z-s->b->a->min_z);
+		if (z < 0)
+			z = 0;
+		if (z > 255)
+			z = 255;
+		p[0] = 255;
+		p[1] = z;
+		p[2] = z;
+		return;
+	}
+	if (zb == UNDEF_F) {
+		z = 128.0*(za-s->a->a->min_z)/(s->a->a->max_z-s->a->a->min_z);
+		if (z < 0)
+			z = 0;
+		if (z > 255)
+			z = 255;
+		p[0] = z;
+		p[1] = 255;
+		p[2] = z;
+		return;
+	}
+
+	z = za;
+	za -= face_z0(s->a, xa, ya);
+	zb -= face_z0(s->b, xa, yb);
+
+	if (za+zb < -s->dist) {
+		p[0] = 0;
+		p[1] = 0;
+		p[2] = 255;
+		return;
+	}
+
+	z = 256.0*(z-s->a->a->min_z)/(s->a->a->max_z-s->a->a->min_z);
+	if (z < 0)
+		z = 0;
+	if (z > 255)
+		z = 255;
+	p[0] = z;
+	p[1] = z;
+	p[2] = z;
+}
+
+
 static void draw_image(GtkWidget *widget, struct solid *s)
 {
 	guchar *rgbbuf, *p;
 	int x, y;
-	double z;
-	struct face *f = s->a;
 
 	rgbbuf = p = calloc(sx(s)*sy(s), 3);
 	if (!rgbbuf) {
@@ -87,24 +148,8 @@ static void draw_image(GtkWidget *widget, struct solid *s)
 	}
 	for (y = sy(s)-1; y >= 0; y--)
 		for (x = 0; x != sx(s) ; x++) {
-			int xa = x+f->a->min_x;
-			int ya = y+f->a->min_y;
-
-			z = zmix(f,
-			    xa*f->m.a[0][0]+ya*f->m.a[0][1]+f->m.b[0],
-			    xa*f->m.a[1][0]+ya*f->m.a[1][1]+f->m.b[1]);
-			if (z == UNDEF_F) {
-				p += 3;
-				continue;
-			}
-			z = 256.0*(z-f->a->min_z)/(f->a->max_z-f->a->min_z);
-			if (z < 0)
-				z = 0;
-			if (z > 255)
-				z = 255;
-			*p++ = z;
-			*p++ = z;
-			*p++ = z;
+			point(s, x, y, p);
+			p += 3;
 		}
 	gdk_draw_rgb_image(widget->window,
 	    widget->style->fg_gc[GTK_STATE_NORMAL],

solidify/solidify.c

@@ -115,7 +115,7 @@ static void gui(void)
 
 static void usage(const char *name)
 {
-	fprintf(stderr, "usage: %s top XXXbottomXXX\n", name);
+	fprintf(stderr, "usage: %s top bottom dist\n", name);
 	exit(1);
 }
 
@@ -124,14 +124,15 @@ int main(int argc, char **argv)
 {
 	gtk_init(&argc, &argv);
 	switch (argc) {
-	case 2:
+	case 4:
 		break;
 	default:
 		usage(*argv);
 	}
 	setlocale(LC_ALL, "C"); /* damage control */
 	solid.a = read_face(argv[1]);
-	solid.b = solid.a;
+	solid.b = read_face(argv[2]);
+	solid.dist = atof(argv[3])/0.025; /* @@@ hack */
 	gui();
 
 	return 0;