I've say snappyHexMesh is smart! It kinda know what I was asking for. This is just the 1st shot and I should be grateful no error throw out right way.
As you can see, I need the air around my "commit rock" to be meshed but not the "commit rock" itself.
Second, only the basement of my commitment are meshed.
Third, too much computation.
Layer mesh : cells:864806 faces:2848196 points:1120129
To project to a plane at y=0.
Use the Calculator filter to project each point (x, y, z) to (x, 0, z).
Turn on Coordinate Results and set the expression to coordsX*iHat + coordsZ*kHat
Use `IntegrateVariables` filter to give you a magic number.
For my profile, the number is: 7591.94.