Align terrain to shape creates spikes or chasms

[LR]

I'm trying to flatten a small hill using a street. However when I run the align terrain to shapes tool, it just punches a chasm in the raster far below the shape. Changing the maximum distance unfortunately only influences to depth of the chasm but does not prevent it. What's the cause of this?

[CherylLau]

That seems strange.  I just tried to align some terrain to a street shape in 2017.0, and it worked for me.

Does this also happen when trying to align the terrain to polygonal shapes (for example, a rectangle or polygon drawn with the polygon draw tool) instead of street shapes?

Would you mind posting your CityEngine project?

[LR]

It just randomly started after a while but when it occurs once it always happens. It doesn't matter if it's streets or polygons. What helped (at least sometimes) was creating a new project and then importing the layer from the new scene. It also seems that using smaller (about 1m²) polygons reduces the chance of this occuring.

I had the problem in 2016 and 2017. Can't share the project but I'll see if I can replicate the error with a smaller sample when I have the time.

[CherylLau]

What does the elevation delta image file look like?  Can you see the strange spikes or chasms in this image?  It can be found in the data folder in the corresponding scene subfolder, and it starts with "elevation_delta".

[LR]

The elevation delta rasters reflect the errors, meaning they have e. g. white spots where spikes are. Still haven't had the time to test this extensively. I forgot to mention that sometimes the elevationDelta would end up being appended multiple times in the layer attribute, like attr elevation = map_01(brightness, 401.10547, 483.9453) + elevationDelta + elevationDelta + elevationDelta.