Today a user asked why when they generate a Cut Fill Map does it put a message up in the Plan View saying Cut Fill Map too dense to display. This is the reasoning and how the settings actually work when generating the Cut Fill map
That message comes up when the number of Grid Points to be created exceeds an internal maximum (set to protect users from creating data that will basically kill the graphics of TBC) - so on a large site an interval of 20 may be too tight for the engine to compute - in that case I would break the job into two parts and create 2x CF Maps one for each half of the project if I had to get the 20 spacings.
Once the CF Maps are created you can add a boundary to break one off as the left half and another boundary to break the other half off - you do not need to break up the Original and Design surfaces to do this
The settings are limited to 1000 spacings in X and 10000 in Y or a max number of 200000 grid spots. For example I have a site which the overlapping surface areas have a max width in X of 1635ft and a mas height in Y of 1053 ft which at 2’ spacings fails because the number of spots would be ~400,000 which fails the 200,000 spot test, and passes at 3 feet because that is only ~191,000 spots and both the X and Y numbers also pass.
So if your site is skewed in one direction you can rotate the orientation of the Cut Fill Map to align the Y axis (which allows more spacings) to the long axis of the site and maybe that will help you fix the issue.
The calculation of the width and height of the area to be covered by the CF Map is based on the Min and Max coordinates of the overlap area between the two surfaces - it does not take into account an irregular shaped boundary to try and reduce the number of nodes in that calculation. In an alignment based surface it does the same but it takes the Min and Max station and the max offsets on Left and right side of the alignment to determine the area of the project for the calculation.
For a linear project if you make the surface an Alignment Based Surface (Surface Properties) then the CF Grid is computed using Station (Y = 10000 spacings which at 20 units = 200,000 units long ie 200km or 200,000 feet) and Offset (X = 1000 spacings) and the grid area will not then be derived from the Min Max coords of the Spatial Area of the project - it will be derived by the Station Length and Offset width which will be a lot smaller and it may then process for you.
If an area based project - then the splitting of the CF Map is likely the only solution to get the interval you want on a big project at this time. Appreciate that this is less than ideal but is a solution if the other options don’t work. I would however say that if you add 200000 pieces of text for a CF Label that TBC will slow down quite a bit while the text is displayed and going much above that or displaying CF and Surface Elevations (600,000 pieces of text) would make TBC pretty hard to use - especially if the text used was a True Type vs a stroked font as true Types are going to be slower to redraw etc.
That setting could be changed (or made user definable), but the developers try to protect the system from someone saying e.g. create a CF Grid at 0.1’ centers over a massive site which would take a long time to compute and then would be almost impossible to display because of all the text items to draw etc.