Update app.py

app.py

@@ -8,7 +8,6 @@ import shapely.geometry
 import pyprt
 import glob
 import shutil
-import pyproj
 from shapely.ops import transform
 from shapely.affinity import translate
 import functools
@@ -569,15 +568,13 @@ async def generate_i3s(request: GenerateRequest):
         if not shape.is_valid:
             shape = shape.buffer(0)
 
-        # 2. Same polygon handling as /generate (ENU-local, centroid at origin).
-        #    One direct ECEF→3857 transform gives the 3857 anchor; ENU offsets are added.
-        cx_3857, cy_3857 = 0.0, 0.0
-        if ecef_center:
-            t = pyproj.Transformer.from_crs("EPSG:4978", "EPSG:3857", always_xy=True)
-            cx_3857, cy_3857, _ = t.transform(ecef_center[0], ecef_center[1], ecef_center[2])
-            logger.info(f"I3S 3857 anchor: ({cx_3857:.1f}, {cy_3857:.1f})")
-        else:
-            logger.warning("No ECEF center — I3S placed at 3857 origin (incorrect)")
+        # 2. ecef_center from Cesium is already EPSG:4978 (ECEF X/Y/Z in metres).
+        #    Use it directly as globalOffset — no projection conversion needed.
+        #    Vertices stay in ENU-local CGA format (small offsets, same as GLB).
+        if not ecef_center:
+            logger.warning("No ECEF center — I3S placed at Earth origin (incorrect)")
+            ecef_center = (0.0, 0.0, 0.0)
+        logger.info(f"I3S ECEF anchor: ({ecef_center[0]:.1f}, {ecef_center[1]:.1f}, {ecef_center[2]:.1f})")
 
         centroid = shape.centroid
         shape_centered = translate(shape, xoff=-centroid.x, yoff=-centroid.y)
@@ -585,8 +582,8 @@ async def generate_i3s(request: GenerateRequest):
         if coords[0] == coords[-1]:
             coords = coords[:-1]
 
-        # Local ENU coords (small, centred on 0,0) — same as /generate GLB.
-        # globalOffset places the local origin at the 3857 anchor in the encoder.
+        # ENU-local CGA vertices: X=east, Y=height=0, Z=-north (same as /generate GLB).
+        # The encoder rotates these local axes to ECEF using globalOffset as the anchor.
         flattened_coords = []
         for p in coords:
             flattened_coords.extend([p[0], 0, -p[1]])
@@ -600,17 +597,19 @@ async def generate_i3s(request: GenerateRequest):
 
         initial_shape = pyprt.InitialShape(flattened_coords, indices, face_counts)
 
-        # 3. Encoder Options — Global scene, Web Mercator (EPSG:3857).
+        # 3. Encoder Options — Global scene, ECEF (EPSG:4978).
+        #    sceneWkid 4978 is required for sceneType 'Global'.
+        #    globalOffset = ECEF anchor; encoder rotates local CGA axes to ECEF at that point.
         layer_id = str(uuid.uuid4())
         output_dir = os.path.join(LAYERS_DIR, layer_id)
         os.makedirs(output_dir, exist_ok=True)
 
-        slpk_name = f"SceneLayer_{layer_id[:18]}"
+        slpk_name = f"SceneLayer_{layer_id[:8]}"
         enc_options = {
             'sceneType':               'Global',
-            #'sceneWkid':               '3857',
-            # globalOffset is in the output CRS (EPSG:3857): [x_easting, y_northing, z_height]
-            #'globalOffset':            [cx_3857, cy_3857, 0.0],
+            'sceneWkid':               '4978',
+            # ECEF anchor — places the local CGA origin at the drawn polygon centroid
+            'globalOffset':            list(ecef_center),
             'baseName':                slpk_name,
             'writePackage':            False,    # unzipped folder; fallback extracts .slpk if unsupported
             'layerTextureEncoding':    ['2'],