diff --git a/src/editor/level_editor.jai b/src/editor/level_editor.jai
index bbf626a..2b7f5f6 100644
--- a/src/editor/level_editor.jai
+++ b/src/editor/level_editor.jai
@@ -498,6 +498,7 @@ add_trile :: (name: string, x: s32, y: s32, z: s32, orientation: u8 = 0) {
 		array_add(*chunk.groups, group);
 	}
 	invalidate_buried_around(*curworld.world, x, y, z);
+	chunk_set_occupancy_mask_at(chunk, lx, ly, lz, true);
 } @Command
 
 remove_trile :: (x: s32, y: s32, z: s32) {
@@ -524,6 +525,7 @@ remove_trile :: (x: s32, y: s32, z: s32) {
 		if removed  break;
 	}
 	if removed  invalidate_buried_around(*curworld.world, x, y, z);
+	chunk_set_occupancy_mask_at(chunk, lx, ly, lz, false);
 } @Command
 
 
diff --git a/src/pseudophysics/worldphysics.jai b/src/pseudophysics/worldphysics.jai
index 65171df..bf101db 100644
--- a/src/pseudophysics/worldphysics.jai
+++ b/src/pseudophysics/worldphysics.jai
@@ -1,15 +1,12 @@
 is_trile_collision :: (fx: float, fy: float, fz: float) -> bool {
-	x := cast(s32)fx;
-	y := cast(s32)fy;
-	z := cast(s32)fz;
+	x := cast(s32)floor(fx);
+	y := cast(s32)floor(fy);
+	z := cast(s32)floor(fz);
 	world := get_current_world();
     key := world_to_chunk_coord(x, y, z);
 	chunk := table_find_pointer(*world.world.chunks, key);
     if !chunk then return false;
 
     lx, ly, lz := world_to_local(x, y, z);
-
-	print("% % %\n", lx, ly, lz);
-
-	return chunk.occupancy_mask[lx][ly][lz];
+	return chunk_get_occupancy_mask_at(chunk, lx, ly, lz);
 }
diff --git a/src/world.jai b/src/world.jai
index 825cb6c..dc8c83e 100644
--- a/src/world.jai
+++ b/src/world.jai
@@ -59,13 +59,38 @@ Chunk :: struct {
     coord:  Chunk_Key;
     groups: [..]Chunk_Trile_Group;
 
-    occupancy_mask : [32][32][32]bool;
+    // This goes x,z,y so y is the bitmask because
+    // that is useful when we're checking for ground under
+    // entities
+    occupancy_mask : [32][32]u32;
 
     sh_probe_grid:  sg_image;  // 192x4096 RGBA16F 2D texture (2 probes/trile/axis)
     sh_valid:       bool;
     sh_dirty:       bool;
 }
 
+// @Note: these are local coords inside the chunk
+chunk_get_occupancy_mask_at :: inline (chunk: *Chunk, lx: u32, ly: u32, lz: u32) -> bool {
+    return (chunk.occupancy_mask[lx][lz] & (cast(u32)1 << ly)) != 0;
+}
+
+// @Note: these are local coords inside the chunk
+chunk_set_occupancy_mask_at :: inline (chunk: *Chunk, lx: u32, ly: u32, lz: u32, occupied: bool) {
+    if occupied {
+        chunk.occupancy_mask[lx][lz] |= (cast(u32)1 << ly);
+    } else {
+        chunk.occupancy_mask[lx][lz] &= ~(cast(u32)1 << ly);
+    }
+}
+
+chunk_clear_full_occupancy_mask :: (chunk: *Chunk) {
+    for i: 0..31 {
+        for j: 0..31 {
+            chunk.occupancy_mask[cast(u32)i][cast(u32)j] = 0;
+        }
+    }
+}
+
 Editor_Note :: struct {
     position : Chunk_Key;
     text     : string;
@@ -100,21 +125,14 @@ World :: struct {
 }
 
 calculate_and_set_chunk_occupancy_mask :: (chunk: *Chunk) {
-    print("Calculating occupancy mask for chunk %\n", chunk.coord);
-    // Clear it first:
-    for i: 0..15 {
-        for j: 0..15 {
-            for k: 0..15 {
-                chunk.occupancy_mask[i][j][k] = false;
-            }
-        }
-    }
+    chunk_clear_full_occupancy_mask(chunk);
     
     for group: chunk.groups {
         // @ToDo: Handle non-colliding triles by getting the
         // trile data here and continuing if it's non-colliding.
         for instance : group.instances {
-            chunk.occupancy_mask[instance.x][instance.y][instance.z] = true;
+            
+            chunk_set_occupancy_mask_at(chunk, instance.x, instance.y, instance.z, true);
         }
     }
 }