Pointmap: inject KHR_materials_unlit into the GLB → no lighting variation, just raw pixel color

app.py

@@ -330,9 +330,57 @@ def _make_glb(image_pil_texture: Image.Image, pointmap_hwc: np.ndarray,
     )
     out_path = tempfile.NamedTemporaryFile(delete=False, suffix=".glb").name
     mesh.export(out_path)
+    _glb_inject_unlit(out_path)   # → render with raw vertex color, no lighting
     return out_path
 
 
+# -----------------------------------------------------------------------------
+# GLB post-processing: inject KHR_materials_unlit extension so Three.js skips
+# all lighting calculations and renders surfels as their raw vertex colour.
+
+import struct
+import json
+
+
+def _glb_inject_unlit(glb_path: str) -> None:
+    """Patch a binary GLB to mark every material as KHR_materials_unlit.
+    glTF spec for the extension: surfaces render with `baseColor` only,
+    no shading from light sources or normals."""
+    with open(glb_path, "rb") as f:
+        data = f.read()
+
+    # GLB header: magic | version | total_length  (12 bytes)
+    if data[:4] != b"glTF":
+        return
+    # First chunk: length(4) | type(4) | payload — JSON chunk.
+    json_len, json_type = struct.unpack_from("<II", data, 12)
+    if json_type != 0x4E4F534A:  # "JSON"
+        return
+    json_bytes = data[20 : 20 + json_len]
+    bin_tail = data[20 + json_len :]   # everything after = BIN chunk(s)
+
+    gltf = json.loads(json_bytes.rstrip(b" \x00").decode("utf-8"))
+    used = gltf.setdefault("extensionsUsed", [])
+    if "KHR_materials_unlit" not in used:
+        used.append("KHR_materials_unlit")
+    for mat in gltf.get("materials", []):
+        mat.setdefault("extensions", {})["KHR_materials_unlit"] = {}
+
+    new_json = json.dumps(gltf, separators=(",", ":")).encode("utf-8")
+    pad = (4 - len(new_json) % 4) % 4
+    new_json += b" " * pad
+
+    new_total = 12 + 8 + len(new_json) + len(bin_tail)
+    out = (
+        b"glTF" + struct.pack("<II", 2, new_total)
+        + struct.pack("<II", len(new_json), 0x4E4F534A)
+        + new_json
+        + bin_tail
+    )
+    with open(glb_path, "wb") as f:
+        f.write(out)
+
+
 # -----------------------------------------------------------------------------
 # Gradio handler