diff --git a/src/c3nav/mapdata/render/engines/base3d.py b/src/c3nav/mapdata/render/engines/base3d.py
index b9be88b2..2c7f2516 100644
--- a/src/c3nav/mapdata/render/engines/base3d.py
+++ b/src/c3nav/mapdata/render/engines/base3d.py
@@ -1,9 +1,10 @@
 from itertools import chain
+from typing import Optional
 
 import numpy as np
 
 from c3nav.mapdata.render.data import HybridGeometry
-from c3nav.mapdata.render.engines.base import RenderEngine
+from c3nav.mapdata.render.engines.base import FillAttribs, RenderEngine, StrokeAttribs
 
 
 class Base3DEngine(RenderEngine):
@@ -22,13 +23,13 @@ class Base3DEngine(RenderEngine):
     def _append_to_vertices(self, vertices, append=None):
         if append is not None:
             append = np.array(append, dtype=np.float32).flatten()
-            vertices = np.hstack((
+            vertices = np.dstack((
                 vertices,
-                append.reshape(1, append.size).repeat(vertices.shape[0], 0)
+                append.reshape(1, append.size).repeat(vertices.shape[0]*3, 0).reshape((-1, 3, append.size))
             ))
         return vertices
 
     def _place_geometry(self, geometry: HybridGeometry, append=None):
         faces = np.vstack(tuple(chain(geometry.faces, *geometry.add_faces.values())))
-        vertices = faces.reshape(-1, 3) * self.np_scale + self.np_offset
+        vertices = faces * self.np_scale + self.np_offset
         return self._append_to_vertices(vertices, append).flatten()
diff --git a/src/c3nav/mapdata/render/engines/opengl.py b/src/c3nav/mapdata/render/engines/opengl.py
index ccda607a..95973f87 100644
--- a/src/c3nav/mapdata/render/engines/opengl.py
+++ b/src/c3nav/mapdata/render/engines/opengl.py
@@ -166,10 +166,10 @@ class OpenGLEngine(Base3DEngine):
         lines = unary_union(lines).buffer(width, cap_style=CAP_STYLE.flat, join_style=JOIN_STYLE.mitre)
 
         vertices, faces = triangulate_polygon(lines)
-        triangles = np.hstack((vertices[faces.flatten()], np.full((faces.size, 1), fill_value=altitude)))
-        vertices = np.vstack(triangles).astype(np.float32) * self.np_scale + self.np_offset
+        triangles = np.dstack((vertices[faces], np.full((faces.size, 1), fill_value=altitude).reshape((-1, 3, 1))))
+        triangles = triangles.astype(np.float32) * self.np_scale + self.np_offset
 
-        return self._append_to_vertices(vertices, append).flatten()
+        return self._append_to_vertices(triangles, append).flatten()
 
     worker = OpenGLWorker()