From f92aa640ce2f2859cc7ba8207ed6d20ed1af4a19 Mon Sep 17 00:00:00 2001
From: John Tsiombikas <nuclear@member.fsf.org>
Date: Wed, 14 Sep 2022 22:54:44 +0300
Subject: [PATCH] add visibility table tool

---
 tools/vistab.c |  117 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 117 insertions(+)
 create mode 100644 tools/vistab.c

diff --git a/tools/vistab.c b/tools/vistab.c
new file mode 100644
index 0000000..6341238
--- /dev/null
+++ b/tools/vistab.c
@@ -0,0 +1,117 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+#define NUM_DIRS	8
+#define MAX_DIST	4
+#define FOV			60
+
+struct cell {
+	int dx, dy;
+};
+
+void calc_vis(int dir);
+int is_visible(float x, float y, float dir);
+
+int main(void)
+{
+	int i;
+
+	printf("struct {int dx, dy;} visoffs[%d][32] = {\n", NUM_DIRS);
+
+	for(i=0; i<NUM_DIRS; i++) {
+
+		printf("\t/* dir %d */\n", i);
+		calc_vis(i);
+	}
+
+	printf("};\n");
+	return 0;
+}
+
+int cellcmp(const void *a, const void *b)
+{
+	const struct cell *ca = a;
+	const struct cell *cb = b;
+	int za = ca->dx * ca->dx + ca->dy * ca->dy;
+	int zb = cb->dx * cb->dx + cb->dy * cb->dy;
+	return zb - za;
+}
+
+void calc_vis(int dir)
+{
+	int i, j, count, col;
+	struct cell vis[512];
+	int x, y;
+	float theta = (float)(dir + 2) / NUM_DIRS * M_PI * 2.0f;
+
+	fprintf(stderr, "DIR: %d (angle: %g)\n", dir, theta * 180.0f / M_PI);
+	count = 0;
+	for(i=0; i<MAX_DIST*2+1; i++) {
+		y = i - MAX_DIST;
+		for(j=0; j<MAX_DIST*2+1; j++) {
+			x = j - MAX_DIST;
+
+			if(is_visible(x, y, theta)) {
+				vis[count].dx = x;
+				vis[count].dy = y;
+				count++;
+
+				fputc('#', stderr);
+			} else {
+				fputc('.', stderr);
+			}
+		}
+		fputc('\n', stderr);
+	}
+	fputc('\n', stderr);
+
+	qsort(vis, count, sizeof *vis, cellcmp);
+
+	printf("\t{");
+	col = 5;
+	for(i=0; i<count; i++) {
+		col += printf("{%d,%d}", vis[i].dx, vis[i].dy);
+		if(i < count - 1) {
+			if(col > 72) {
+				fputs(",\n\t ", stdout);
+				col = 5;
+			} else {
+				fputs(", ", stdout);
+				col += 2;
+			}
+		}
+	}
+	fputs(dir < NUM_DIRS - 1 ? "},\n" : "}\n", stdout);
+}
+
+#define RAD 1.42
+
+float ptlinedist(float x, float y, float dir)
+{
+	return -y * cos(dir) + sin(dir) * x;
+}
+
+int is_visible(float x, float y, float dir)
+{
+	static const char voffs[][2] = {{-0.5, -0.5}, {0.5, -0.5}, {0.5, 0.5}, {-0.5, 0.5}};
+	float d0, d1;
+	int i;
+	float hfov = 0.5f * FOV * M_PI / 180.0f;
+
+	d0 = ptlinedist(x, y, dir - hfov);
+	d1 = ptlinedist(x, y, dir + hfov);
+	if(d0 >= 0 && d1 <= 0) {
+		return 1;
+	}
+
+	for(i=0; i<4; i++) {
+		d0 = ptlinedist(x + voffs[i][0], y + voffs[i][1], dir - hfov);
+		d1 = ptlinedist(x + voffs[i][0], y + voffs[i][1], dir + hfov);
+
+		if(d0 >= 0 && d1 <= 0) {
+			return 1;
+		}
+	}
+	return 0;
+}
-- 
1.7.10.4