volume calculation??

[thanhtike.myn]

In order to compute volume, shall we have at least 2 suface or possible to compute without any comparison surface?

Thanhtike

[Anonymous]

Essentially yes, you need two surfaces.  For example, you can have an existing grade and then use say a building pad outline as a feature line and grade to an existing surface which will create a new surface in order to do volume calculations hence the second surface.  I am currently working on a building pad that I am setting an elevation to 1000' and I have contours that I of the existing grade (above and below 1000').  I created a surface from the contours to create my existing grade surface (surface 1). Then my pad outline (simple 20 x 20 square) was drawn using a polyline then converted to a feature line.  Assigned an elevation to the feature line.  Then used grading tools to set a grading group and gave it a target surface which will ask if this will be for volume and check the box to essentially agree.  Then a surface tin box appears to create surface 2.  I would look at a tutorial for a better explanation. 

[Neilw_05]

If you want to use C3D to compute volumes you will need 2 surfaces, but you can also get volumes from 3D linework using basic Autocad.

You don't have to have an existing ground surface to get volumes in C3D. For example if you want to calculate the volume of a cube, you could create a surface representing the top of the cube and a surface representing the sides and bottom. The volume would be the difference between the top surface vs. the sides and bottom surface.

[thanhtike.myn]

yes,thats why i asked we must have 2 surfaces even in one object ,right? we have to create 2 surfaces like top surface and other one. 

[Neilw_05]

As I said, you will need 2 Civil 3D surfaces to compute TIN volumes, but Autocad will report the volume of 3D objects such as spheres, cubes or surfaces created from meshes etc.