Another issue with 4.27 that we encountered in our Paper2D game is that tilemap editing breaks when a tilemap grows too large in the Y direction (too deep). When that happens, tiles cannot be selected or edited when viewing the tilemap with the default viewport Orthographic, Right).
After a lot of debugging we figured out that it was due to the raycast that figures out which tile is underneath the cursor doesn’t start from in front of the tilemap object. This means that the raycast always misses and nothing can be selected.
This happens when a tilemap grows to above 300-400 units deep in the Y direction. We have tilemaps with 12-15 layers, with 32 units of separation between each layer, so this happens for us with pretty much all our tilemaps.
Why does this happen? Well, the raycast starting position is determined based on the Bounds of the tilemap object (for some reason).
Our solution was to modify GetDesiredFocusBounds() in TileMapEditorViewportClient.cpp as so:
FBox FTileMapEditorViewportClient::GetDesiredFocusBounds() const
{
FBox Bounds = RenderTileMapComponent->Bounds.GetBox();
Bounds.Min.Y = 0.f;
Bounds.Max.Y = 0.f;
return Bounds;
}
This makes the raycast start from Y=0 regardless of the size of the tilemap, and now the raycast hits regardless of the size of the tilemap. 