Initial independent commit

1 files changed, 97 insertions, 0 deletions

diff --git a/src/fov.c b/src/fov.c
new file mode 100644
index 0000000..cdc7dc8
--- /dev/null
+++ b/src/fov.c
@@ -0,0 +1,97 @@
+#include <stdint.h>
+#include <math.h>
+#include <engine/fov.h>
+#include <engine/utils.h>
+
+void fov_shadowcast_rec(const void *map, const v2_i32 mapsize,
+                        bool (*visblocking)(const void*), i32 *lightmap,
+                        const i32 range, v2_i32 src,
+                        const i32 row,
+                        f32 start, const f32 end,
+                        const i8 xx, const i8 xy, const i8 yx, const i8 yy) {
+
+	if (start < end) return;
+
+	const i32 range_2 = range * range;
+	f32 new_start   = start;
+
+	for (i32 i = row; i <= range; i++) {
+		i32 dx = (-1 * i) - 1;
+		i32 dy =  -1 * i;
+
+		bool blocked = false;
+
+		while (dx <= 0) {
+			dx += 1;
+
+			const i32 mapx = src.x + dx * xx + dy * xy;
+			const i32 mapy = src.y + dx * yx + dy * yy;
+
+			const f32 slope_l = (((f32)dx) - 0.5f) / (((f32)dy) + 0.5f);
+			const f32 slope_r = (((f32)dx) + 0.5f) / (((f32)dy) - 0.5f);
+
+			if (start < slope_r) continue;
+			if (end   > slope_l) break;
+
+			if (dx * dx + dy * dy < range_2) {
+				/* set as visible */
+				if (mapx >= 0 && mapx < (long)mapsize.x
+				&&  mapy >= 0 && mapy < (long)mapsize.y) {
+					// TODO: Calculate proper dist from source
+					f32 x_2 = (src.x - mapx) * (src.x - mapx);
+					f32 y_2 = (src.y - mapy) * (src.y - mapy);
+					lightmap[mapy*mapsize.x + mapx] = MAX(lightmap[mapy*mapsize.x + mapx], range - sqrt((f32)(x_2 + y_2)));
+				}
+			}
+
+			/* sizeof(i32) is the size of enums */
+			/* -- unless the compiler doesn't follow standard behaviour */
+			const bool is_blocked = visblocking(
+				(void*)((u64)map
+				       + sizeof(i32)               /* ~ enum size */
+				       * (mapsize.x * mapy + mapx) /* index */
+				));
+
+			if (blocked) {
+				if (!is_blocked) {
+					new_start = slope_r;
+				} else {
+					blocked = false;
+					start = new_start;
+				}
+			} else if (!is_blocked && i < range) {
+				blocked = true;
+				fov_shadowcast_rec(map, mapsize, visblocking, lightmap, range, src, i+1, start, slope_l, xx, xy, yx, yy);
+				new_start = slope_r;
+			}
+		}
+
+		if (blocked) break;
+	}
+}
+
+/* http://www.roguebasin.com/index.php?title=FOV_using_recursive_shadowcasting */
+void fov_shadowcast(const void *map, const v2_i32 mapsize,
+                    bool (*visblocking)(const void*), i32 *lightmap,
+                    const i32 range, const v2_i32 src) {
+
+	const i8 m[4][8] = {
+		{1,  0,  0, -1, -1,  0,  0,  1},
+		{0,  1, -1,  0,  0, -1,  1,  0},
+		{0,  1,  1,  0,  0, -1, -1,  0},
+		{1,  0,  0,  1, -1,  0,  0, -1},
+	};
+
+	for (i32 oct = 0; oct < 8; oct++) {
+		fov_shadowcast_rec(
+		    map, mapsize, visblocking, lightmap, range, src,
+		    1, 1.0, 0.0,
+		    m[0][oct],
+		    m[1][oct],
+		    m[2][oct],
+		    m[3][oct]);
+	}
+
+	/* The center is the most lit square */
+	lightmap[src.y * mapsize.x + src.x] = range;
+}