fix buffer geometry indexing bug

Author: Licini

scripts/buffer.py

@@ -3,14 +3,17 @@
 from compas_viewer import Viewer
 from compas_viewer.scene import BufferGeometry
 
+# One vertex per point
 points = np.random.rand(1000, 3) * 10
 pointcolor = np.random.rand(1000, 4)
 
-lines = np.random.rand(1000 * 6, 3) * 10
-linecolor = np.random.rand(1000 * 6, 4)
+# Two vertices per line
+lines = np.random.rand(1000 * 2, 3) * 10
+linecolor = np.random.rand(1000 * 2, 4)
 
-faces = np.random.rand(1000 * 9, 3) * 10
-facecolor = np.random.rand(1000 * 9, 4)
+# Three vertices per face
+faces = np.random.rand(1000 * 3, 3) * 10
+facecolor = np.random.rand(1000 * 3, 4)
 
 geometry = BufferGeometry(points=points, pointcolor=pointcolor, lines=lines, linecolor=linecolor, faces=faces, facecolor=facecolor)
 
@@ -23,10 +26,10 @@ def update(frame):
 
     geometry.points = np.random.rand(1000, 3) * 10
     geometry.pointcolor = np.random.rand(1000, 4)
-    geometry.lines = np.random.rand(1000 * 6, 3) * 10
-    geometry.linecolor = np.random.rand(1000 * 6, 4)
-    geometry.faces = np.random.rand(1000 * 9, 3) * 10
-    geometry.facecolor = np.random.rand(1000 * 9, 4)
+    geometry.lines = np.random.rand(1000 * 2, 3) * 10
+    geometry.linecolor = np.random.rand(1000 * 2, 4)
+    geometry.faces = np.random.rand(1000 * 3, 3) * 10
+    geometry.facecolor = np.random.rand(1000 * 3, 4)
 
     obj.update(update_data=True)
 

src/compas_viewer/scene/bufferobject.py

@@ -122,13 +122,24 @@ def __init__(self, *args, show_points: bool = True, show_lines: bool = True, sho
     def buffergeometry(self) -> BufferGeometry:
         return self.item
 
+    def _get_num_vertices(self, positions: NDArray) -> int:
+        """Get the number of vertices from positions array.
+
+        Handles both flat 1D arrays [x1, y1, z1, x2, y2, z2, ...] and
+        2D arrays with shape (N, 3).
+        """
+        if positions.ndim == 1:
+            return positions.shape[0] // 3
+        else:
+            return positions.shape[0]
+
     def _read_points_data(self):
         """Read points data from the object."""
         if self.buffergeometry.points is None:
             return None
         positions = self.buffergeometry.points
         colors = self.buffergeometry.pointcolor
-        elements = np.arange(positions.shape[0] // 3, dtype=int)
+        elements = np.arange(self._get_num_vertices(positions), dtype=int)
         return positions, colors, elements
 
     def _read_lines_data(self):
@@ -137,7 +148,7 @@ def _read_lines_data(self):
             return None
         positions = self.buffergeometry.lines
         colors = self.buffergeometry.linecolor
-        elements = np.arange(positions.shape[0] // 3, dtype=int)
+        elements = np.arange(self._get_num_vertices(positions), dtype=int)
         return positions, colors, elements
 
     def _read_frontfaces_data(self):
@@ -146,7 +157,7 @@ def _read_frontfaces_data(self):
             return None
         positions = self.buffergeometry.faces
         colors = self.buffergeometry.facecolor
-        elements = np.arange(positions.shape[0] // 3, dtype=int)
+        elements = np.arange(self._get_num_vertices(positions), dtype=int)
         return positions, colors, elements
 
     def _read_backfaces_data(self):
@@ -155,5 +166,5 @@ def _read_backfaces_data(self):
             return None
         positions = self.buffergeometry.faces
         colors = self.buffergeometry.facecolor
-        elements = np.flip(np.arange(positions.shape[0] // 3, dtype=int))
+        elements = np.flip(np.arange(self._get_num_vertices(positions), dtype=int))
         return positions, colors, elements