Why are all the points from my point cloud not being used to generate the surface? We receive this question fairly often from users who are working with Point Clouds and want to create surface from them. This is due to a few different factors, and the first thing to understand is that Civil 3D creates the surface from the points that are displayed. So that means if only 1,000 points are displayed, that is what is used for the surface creation.
Now there are some additional options you need to pay attention to in order to fully understand the results you are seeing. Civil 3D has a limit of 1.5 million points displayed at one time. If you are zoomed all the way out on your entire point cloud of 5 million points, only 1.5 million will be displayed at one time. Another thing to pay attention to is the Point Density Slider which will control the display of the points as well. So if you want your surface to take in as many points as possible you will want to move this slider to 100.
All that being said, adding all these points is usually not necessary as they are not all needed to accurately represent the surface with the TIN model. Not to mention the file size may become quite large when dealing with that many points added to a surface.