Merge pull request #79 from scd31/world_scale

allow custom world scales

src/args.rs

@@ -29,6 +29,10 @@ pub struct Args {
     #[arg(long, default_value = "requests")]
     pub downloader: String,
 
+    /// World scale to use, in blocks per meter
+    #[arg(long, default_value = "1.0")]
+    pub scale: f64,
+
     /// Enable debug mode (optional)
     #[arg(long, default_value_t = false, action = clap::ArgAction::SetTrue)]
     pub debug: bool,

src/osm_parser.rs

@@ -116,36 +116,20 @@ fn lat_lon_to_minecraft_coords(
     lat: f64,
     lon: f64,
     bbox: (f64, f64, f64, f64), // (min_lon, min_lat, max_lon, max_lat)
-    scale_factor_x: f64,
     scale_factor_z: f64,
+    scale_factor_x: f64,
 ) -> (i32, i32) {
     let (min_lon, min_lat, max_lon, max_lat) = bbox;
 
     // Calculate the relative position within the bounding box
-    let rel_x: f64 = 1.0 - (lat - min_lat) / (max_lat - min_lat);
-    let rel_z: f64 = (lon - min_lon) / (max_lon - min_lon);
+    let rel_x: f64 = (lon - min_lon) / (max_lon - min_lon);
+    let rel_z: f64 = 1.0 - (lat - min_lat) / (max_lat - min_lat);
 
     // Apply scaling factors for each dimension and convert to Minecraft coordinates
     let x: i32 = (rel_x * scale_factor_x) as i32;
     let z: i32 = (rel_z * scale_factor_z) as i32;
 
-    (z, x) // Swap x and z coords to avoid a mirrored projection on the Minecraft map
-}
-
-/// Function to determine the number of decimal places in a float as a string
-fn count_decimal_places(value: f64) -> usize {
-    let s: String = value.to_string();
-    if let Some(pos) = s.find('.') {
-        s.len() - pos - 1 // Number of digits after the decimal point
-    } else {
-        0
-    }
-}
-
-/// Function to convert f64 to an integer based on the number of decimal places
-fn convert_to_scaled_int(value: f64, max_decimal_places: usize) -> i64 {
-    let multiplier: i64 = 10_i64.pow(max_decimal_places as u32); // Compute multiplier
-    (value * multiplier as f64).round() as i64 // Scale and convert to integer
+    (x, z)
 }
 
 pub fn parse_osm_data(
@@ -159,40 +143,10 @@ pub fn parse_osm_data(
     let data: OsmData =
         serde_json::from_value(json_data.clone()).expect("Failed to parse OSM data");
 
-    // Calculate the maximum number of decimal places in bbox elements
-    let max_decimal_places: usize = [
-        count_decimal_places(bbox.0),
-        count_decimal_places(bbox.1),
-        count_decimal_places(bbox.2),
-        count_decimal_places(bbox.3),
-    ]
-    .into_iter()
-    .max()
-    .unwrap();
-
-    // Convert each element to a scaled integer
-    let bbox_scaled: (i64, i64, i64, i64) = (
-        convert_to_scaled_int(bbox.0, max_decimal_places),
-        convert_to_scaled_int(bbox.1, max_decimal_places),
-        convert_to_scaled_int(bbox.2, max_decimal_places),
-        convert_to_scaled_int(bbox.3, max_decimal_places),
-    );
-
     // Determine which dimension is larger and assign scale factors accordingly
-    let (scale_factor_x, scale_factor_z) =
-        if (bbox_scaled.2 - bbox_scaled.0) > (bbox_scaled.3 - bbox_scaled.1) {
-            // Longitude difference is greater than latitude difference
-            (
-                ((bbox_scaled.3 - bbox_scaled.1) * 14 / 100) as f64, // Scale for width (x) is based on latitude difference
-                ((bbox_scaled.2 - bbox_scaled.0) * 10 / 100) as f64, // Scale for length (z) is based on longitude difference
-            )
-        } else {
-            // Latitude difference is greater than or equal to longitude difference
-            (
-                ((bbox_scaled.2 - bbox_scaled.0) * 14 / 100) as f64, // Scale for width (x) is based on longitude difference
-                ((bbox_scaled.3 - bbox_scaled.1) * 10 / 100) as f64, // Scale for length (z) is based on latitude difference
-            )
-        };
+    let (scale_factor_z, scale_factor_x) = geo_distance(bbox.1, bbox.3, bbox.0, bbox.2);
+    let scale_factor_z = scale_factor_z.floor() * args.scale;
+    let scale_factor_x = scale_factor_x.floor() * args.scale;
 
     if args.debug {
         println!("Scale factor X: {}", scale_factor_x);
@@ -209,7 +163,7 @@ pub fn parse_osm_data(
         if element.r#type == "node" {
             if let (Some(lat), Some(lon)) = (element.lat, element.lon) {
                 let (x, z) =
-                    lat_lon_to_minecraft_coords(lat, lon, bbox, scale_factor_x, scale_factor_z);
+                    lat_lon_to_minecraft_coords(lat, lon, bbox, scale_factor_z, scale_factor_x);
 
                 let processed = ProcessedNode {
                     id: element.id,
@@ -309,7 +263,7 @@ pub fn parse_osm_data(
         }));
     }
 
-    (processed_elements, scale_factor_z, scale_factor_x)
+    (processed_elements, scale_factor_x, scale_factor_z)
 }
 
 const PRIORITY_ORDER: [&str; 6] = [
@@ -327,3 +281,36 @@ pub fn get_priority(element: &ProcessedElement) -> usize {
     // Return a default priority if none of the tags match
     PRIORITY_ORDER.len()
 }
+
+// (lat meters, lon meters)
+fn geo_distance(lat1: f64, lat2: f64, lon1: f64, lon2: f64) -> (f64, f64) {
+    let z = lat_distance(lat1, lat2);
+
+    // distance between two lons depends on their latitude. In this case we'll just average them
+    let x = lon_distance((lat1 + lat2) / 2.0, lon1, lon2);
+
+    (z, x)
+}
+
+// Haversine but optimized for a latitude delta of 0
+// returns meters
+fn lon_distance(lat: f64, lon1: f64, lon2: f64) -> f64 {
+    const R: f64 = 6371_000.0;
+    let d_lon = (lon2 - lon1).to_radians();
+    let a =
+        lat.to_radians().cos() * lat.to_radians().cos() * (d_lon / 2.0).sin() * (d_lon / 2.0).sin();
+    let c = 2.0 * a.sqrt().atan2((1.0 - a).sqrt());
+
+    R * c
+}
+
+// Haversine but optimized for a longitude delta of 0
+// returns meters
+fn lat_distance(lat1: f64, lat2: f64) -> f64 {
+    const R: f64 = 6371_000.0;
+    let d_lat = (lat2 - lat1).to_radians();
+    let a = (d_lat / 2.0).sin() * (d_lat / 2.0).sin();
+    let c = 2.0 * a.sqrt().atan2((1.0 - a).sqrt());
+
+    R * c
+}