How can i calculate the volume on amorphous terrain?

[ajdkftls]

 I'm going to put the extrude on top of the toposolid. Is there a way to find the volume of only the part on top of the amorphous terrain?

[constantin.stroescu · Accepted solution]

Use Join function , as can be seen in my short screencast:

https://www.youtube.com/watch?v=vSFe1ZKcqsc

[ToanDN · Accepted solution]

Male the topo solid thicker so the bottom of the toposolid is lower than the the bottom of the blue form.  Join them and switch join order so that the terrain cut the form.  Create a material takeoff schedule to get the remaining volume of the form.