1 files changed, 83 insertions, 0 deletions
diff --git a/src/proc_gen/herringbone.rs b/src/proc_gen/herringbone.rs
new file mode 100644
index 0000000..5e930ec
--- /dev/null
+++ b/src/proc_gen/herringbone.rs
@@ -0,0 +1,83 @@
+use fxhash::hash32;
+use glam::IVec2;
+
+use crate::{
+    config::TILESET_SCALING,
+    content::materials::MaterialId,
+    proc_gen::tileset_loader::{Tile, TileOrientation, Tileset, TilesetPixelType},
+    sim::cell::Cell,
+};
+
+fn split_position(world: IVec2, tileset: &Tileset) -> (IVec2, IVec2, TileOrientation) {
+    let s = tileset.dimensions.short as i32;
+    let tx = world.x.div_euclid(s);
+    let ty = world.y.div_euclid(s);
+    let fx = world.x.rem_euclid(s);
+    let fy = world.y.rem_euclid(s);
+
+    match (tx - ty).rem_euclid(4) {
+        // left half of horizontal tile
+        0 => (
+            IVec2::new(tx, ty),
+            IVec2::new(fx, fy),
+            TileOrientation::Horizontal,
+        ),
+        // right half of horizontal tile
+        1 => (
+            IVec2::new(tx - 1, ty),
+            IVec2::new(fx + s, fy),
+            TileOrientation::Horizontal,
+        ),
+        // top half of vertical tile
+        3 => (
+            IVec2::new(tx, ty),
+            IVec2::new(fx, fy),
+            TileOrientation::Vertical,
+        ),
+        // bottom half of vertical tile
+        2 => (
+            IVec2::new(tx, ty - 1),
+            IVec2::new(fx, fy + s),
+            TileOrientation::Vertical,
+        ),
+        _ => unreachable!(),
+    }
+}
+
+// better "%" for hashes since it prefers the high bits
+#[inline]
+fn reduce(h: u32, n: usize) -> usize {
+    (((h as u128) * (n as u128)) >> 32) as usize
+}
+
+fn pick_variant(tile_pos: IVec2, orientation: TileOrientation, tileset: &Tileset) -> &Tile {
+    let h = hash32(&tile_pos);
+    match orientation {
+        TileOrientation::Horizontal => {
+            &tileset.horizontal_tiles[reduce(h, tileset.horizontal_tiles.len())]
+        }
+        TileOrientation::Vertical => {
+            &tileset.vertical_tiles[reduce(h, tileset.vertical_tiles.len())]
+        }
+    }
+}
+
+// TODO: optimize
+fn get_pixel_at_position(world: IVec2, tileset: &Tileset) -> TilesetPixelType {
+    let scaled_world = world.div_euclid(IVec2::new(TILESET_SCALING, TILESET_SCALING));
+    let (tile_pos, local, orientation) = split_position(scaled_world, tileset);
+    let tile = pick_variant(tile_pos, orientation, tileset);
+    let width = match orientation {
+        TileOrientation::Horizontal => tileset.dimensions.long as i32,
+        TileOrientation::Vertical => tileset.dimensions.short as i32,
+    };
+    tile.pixels[(local.x + local.y * width) as usize]
+}
+
+pub fn get_cell_at_position(world: IVec2, tileset: &Tileset) -> Cell {
+    let pixel = get_pixel_at_position(world, tileset);
+    match pixel {
+        TilesetPixelType::Void => Cell::void(),
+        TilesetPixelType::Terrain => Cell::from_material(MaterialId::Dirt),
+    }
+}