Add generated area border wall option

worldgen-c/include/worldgen.h

@@ -77,6 +77,8 @@ typedef struct {
 	int sea_level;
 	int world_seed;
 	int enable_trails;
+	int enable_wall;
+	int wall_min_x, wall_max_x, wall_min_z, wall_max_z;
 	int snow_line;
 	struct trail_segment *trail_segments;
 	size_t trail_segment_count;

worldgen-c/src/main.c

@@ -51,6 +51,8 @@ typedef struct {
 	int snow_line;
 	pthread_mutex_t *log_mu;
 	int enable_trails;
+	int enable_wall;
+	int wall_min_x, wall_max_x, wall_min_z, wall_max_z;
 	results_buffer *results;
 	struct trail_segment *trail_segments;
 	size_t trail_segment_count;
@@ -593,7 +595,7 @@ static void write_regions(const char *out_dir, region_accum *regions, size_t reg
 static void usage(const char *prog) {
 	fprintf(stderr,
 	        "Usage: %s [--radius R] [--center-x X --center-z Z] [--min-x MX --max-x MX --min-z MZ --max-z MZ]\n"
-	        "          [--threads N] [--seed S] [--sea-level L] [--snow-line H] [--format mca|bin] [--trails] [--out DIR]\n",
+	        "          [--threads N] [--seed S] [--sea-level L] [--snow-line H] [--format mca|bin] [--trails] [--wall] [--out DIR]\n",
 	        prog);
 }
 
@@ -665,6 +667,11 @@ static void *worker_fn(void *ptr) {
 	worldgen_ctx ctx;
 	worldgen_init(&ctx, args->world_seed, args->sea_level, args->snow_line);
 	ctx.enable_trails = args->enable_trails;
+	ctx.enable_wall = args->enable_wall;
+	ctx.wall_min_x = args->wall_min_x;
+	ctx.wall_max_x = args->wall_max_x;
+	ctx.wall_min_z = args->wall_min_z;
+	ctx.wall_max_z = args->wall_max_z;
 	if (args->trail_segments && args->trail_segment_count > 0) {
 		ctx.trail_segments = args->trail_segments;
 		ctx.trail_segment_count = args->trail_segment_count;
@@ -714,6 +721,7 @@ int main(int argc, char **argv) {
 	int sea_level = 70;
 	int snow_line = INT_MIN;
 	int enable_trails = 0;
+	int enable_wall = 0;
 	const char *out_dir = "output";
 	output_format format = FORMAT_MCA;
 
@@ -759,6 +767,8 @@ int main(int argc, char **argv) {
 			}
 		} else if (strcmp(argv[i], "--trails") == 0) {
 			enable_trails = 1;
+		} else if (strcmp(argv[i], "--wall") == 0) {
+			enable_wall = 1;
 		} else if ((strcmp(argv[i], "--out") == 0 || strcmp(argv[i], "--output") == 0) && i + 1 < argc) {
 			out_dir = argv[++i];
 		} else if (strcmp(argv[i], "--help") == 0) {
@@ -789,6 +799,11 @@ int main(int argc, char **argv) {
 	int world_max_x = max_x * CHUNK_SIZE + (CHUNK_SIZE - 1);
 	int world_min_z = min_z * CHUNK_SIZE;
 	int world_max_z = max_z * CHUNK_SIZE + (CHUNK_SIZE - 1);
+	pre_ctx.enable_wall = enable_wall;
+	pre_ctx.wall_min_x = world_min_x;
+	pre_ctx.wall_max_x = world_max_x;
+	pre_ctx.wall_min_z = world_min_z;
+	pre_ctx.wall_max_z = world_max_z;
 	if (enable_trails) {
 		worldgen_prepass(&pre_ctx, world_min_x, world_max_x, world_min_z, world_max_z);
 		prepass_ready = 1;
@@ -834,6 +849,11 @@ int main(int argc, char **argv) {
 		.snow_line = snow_line,
 		.log_mu = &log_mu,
 		.enable_trails = enable_trails,
+		.enable_wall = enable_wall,
+		.wall_min_x = world_min_x,
+		.wall_max_x = world_max_x,
+		.wall_min_z = world_min_z,
+		.wall_max_z = world_max_z,
 		.results = &results,
 		.trail_segments = prepass_ready ? pre_ctx.trail_segments : NULL,
 		.trail_segment_count = prepass_ready ? pre_ctx.trail_segment_count : 0,

worldgen-c/src/worldgen.c

@@ -138,6 +138,7 @@ static void generate_chunk_redwood_floor(worldgen_ctx *ctx, int chunk_x, int chu
 static void generate_chunk_grass(worldgen_ctx *ctx, int chunk_x, int chunk_z, column_data columns[CHUNK_SIZE][CHUNK_SIZE], chunk_data *out);
 static void generate_chunk_flowers(worldgen_ctx *ctx, int chunk_x, int chunk_z, column_data columns[CHUNK_SIZE][CHUNK_SIZE], chunk_data *out);
 static void generate_chunk_cabins(worldgen_ctx *ctx, int chunk_x, int chunk_z, column_data columns[CHUNK_SIZE][CHUNK_SIZE], chunk_data *out);
+static void generate_chunk_border_wall(worldgen_ctx *ctx, int chunk_x, int chunk_z, chunk_data *out);
 static void ensure_trail_prepass(worldgen_ctx *ctx, int chunk_x, int chunk_z);
 static void append_trail_segment(worldgen_ctx *ctx, int ax, int az, int bx, int bz, int *points, int count);
 static int *smooth_trail_polyline(worldgen_ctx *ctx, int *points, int count, int *out_count);
@@ -3553,6 +3554,47 @@ static void generate_chunk_trails(worldgen_ctx *ctx, int chunk_x, int chunk_z, c
 	}
 }
 
+static void generate_chunk_border_wall(worldgen_ctx *ctx, int chunk_x, int chunk_z, chunk_data *out) {
+	if (!ctx->enable_wall) return;
+	if (ctx->wall_min_x > ctx->wall_max_x || ctx->wall_min_z > ctx->wall_max_z) return;
+
+	const int wall_height = 9;
+	for (int dx = 0; dx < CHUNK_SIZE; ++dx) {
+		for (int dz = 0; dz < CHUNK_SIZE; ++dz) {
+			int world_x = chunk_x * CHUNK_SIZE + dx;
+			int world_z = chunk_z * CHUNK_SIZE + dz;
+			if (world_x < ctx->wall_min_x || world_x > ctx->wall_max_x) continue;
+			if (world_z < ctx->wall_min_z || world_z > ctx->wall_max_z) continue;
+
+			int on_border = world_x == ctx->wall_min_x || world_x == ctx->wall_max_x ||
+			                world_z == ctx->wall_min_z || world_z == ctx->wall_max_z;
+			if (!on_border) continue;
+
+			column_data data = get_column_data(ctx, world_x, world_z);
+			int visible_base = data.height;
+			if (data.has_water && data.water_surface > visible_base) {
+				visible_base = data.water_surface;
+			}
+			if (visible_base >= CHUNK_HEIGHT - 1) continue;
+
+			int top = visible_base + wall_height;
+			if (top >= CHUNK_HEIGHT) top = CHUNK_HEIGHT - 1;
+
+			for (int y = data.height + 1; y < CHUNK_HEIGHT; ++y) {
+				out->blocks[y][dx][dz] = BLOCK_AIR;
+			}
+			out->heightmap[dx][dz] = (uint16_t)data.height;
+
+			int start = data.height + 1;
+			if (start < 1) start = 1;
+			for (int y = start; y <= top; ++y) {
+				uint16_t block = (y == top) ? BLOCK_OAK_PLANKS : BLOCK_STONE;
+				set_block_with_height(out, dx, dz, y, block);
+			}
+		}
+	}
+}
+
 // ---------------------------------------------------------------------------
 // Public API
 // ---------------------------------------------------------------------------
@@ -3561,6 +3603,9 @@ void worldgen_init(worldgen_ctx *ctx, int world_seed, int sea_level, int snow_li
 	ctx->sea_level = sea_level;
 	ctx->snow_line = snow_line;
 	ctx->enable_trails = 0;
+	ctx->enable_wall = 0;
+	ctx->wall_min_x = ctx->wall_max_x = 0;
+	ctx->wall_min_z = ctx->wall_max_z = 0;
 	ctx->trail_segments = NULL;
 	ctx->trail_segment_count = 0;
 	ctx->trail_segment_cap = 0;
@@ -3650,4 +3695,6 @@ void worldgen_generate_chunk(worldgen_ctx *ctx, int chunk_x, int chunk_z, chunk_
 		}
 	}
 	block_list_free(&trees);
+
+	generate_chunk_border_wall(ctx, chunk_x, chunk_z, out);
 }