Project: QGIS
Version: 3.2.0
Sometimes datasets with 3D polygons do not have consistent ordering of vertices (clockwise vs. counter-clockwise) and that caused sub-optimal results in the 3D view: either some polygons (walls) seem to be missing if back-face culling is enabled - or some polygons are shaded incorrectly if back-face culling is disabled. With the new option Add back faces enabled, the tessellator will generate triangles in both directions (front and back) which greatly improves the rendering quality for such datasets.
The only downside when using this option is that more graphical memory is used (double amount of vertex data). Make sure to set culling mode to "Back" when using this option, otherwise there would be no visible difference as the scene would still render polygons with incorrect shading.
The image contains freely available Prague 3D buildings dataset.
This feature was developed by Martin Dobias (Lutra Consulting)