How to not interpolate in the blank without point cloud when build DTM？

[QAQ0w0]

Because the shape of my file is irregular, there are some prominent ground points.When build DTM with lidR，points will be generated by interpolation in some places that do not belong to my work area.
such as this picture，blue area is my work area，and red area before dtm is blank ，but after building dtm this area become a ground in dtm

[Jean-Romain]

There are multiple solutions. tin() has a parameter max_edge. rasterize_terrain has generic argument shape

[QAQ0w0]

Is this feature not available in version 3.2.0? I haven't upgraded to version 4.0.0 yet

[Jean-Romain]

Yes but not exactly implemented the same way. Anyway, please update