How to sum two surfaces

[viriato79]

Hi

I would like to know if this is possible:

 

I have two surfaces, A and B.

I want to create a surface C, with the same x,y reference, but with a z = z(A)+z(B)

The result will be a surface with the sum of elevatios of A and B.

 

Thanks

[BIGAL]

No idea why you would sum the elevations is it because you want to exagerate the z for 3d viewing ?

[viriato79]

No, I use 3d Surfaces to simulate irrigation water depht. Each surface will be a 3d model of a sprinkler water distribuition in flat ground. I would like to overlap sprinklers and sum water depths = sum surface heights.

Thanks

[alanjt]

Paste one surface into the other and raise the surface.

[viriato79]

Paste one surface into the other and raise the surface.

 

Can you be a little more specific. What is the procedure? thanks

[alanjt]

Can you be a little more specific. What is the procedure? thanks

Open the editor (toolspace), look at the edit properties for one surface, select 'paste surface' and pick the other surface. Look at your 'Surfaces' pulldown and under 'Edit Surface' there will be a command called 'Raise/Lower Surface'.

[viriato79]

When I past a surface A over another B, there is no sum of heights. the pasted surface heights A will replace the heights of B. not added to B.

[LukeT]

Have you tried inverting the z values of surface B, then doing a volume surface between surface A and the inverted surface B.

[BIGAL]

You refer to irragation and I assume water is always flat (please nothing about windy day and water flowing up hill), Ok the sum of the heights is not the water depth rather you want the difference between the two surfaces as a volume. ie surface 1 natural - surface 2 a water body. It becomes tricky when the natural pokes islands into the water body, but the volume difference between surface 1 and 2 will give cut and fill one of these values is your water volume. Just look up "volume between two surfaces" You can also do stuff like grids and difference in height.

[viriato79]

this is what I would like to do, not in 2d but in a 3d.

[LukeT]

First up, the diagrams aren't reading like its an addition of z values. As they are 2d graphs of X vs Z, row 1 overlapped on row 2 = same shape, not what is shown in row 3.

Then looking at row 3 -> 4, that also doesnt match up. But lets ignore that for now.

 

I dont have CAD available in front of me so cant think of anything more elegant right now, but I will elaborate on my previous suggestion:

 

1) Start with Surface A and Surface B

2) Make a new surface C at zero elevation. just a flat plane. (extract border from A or B or just draw polyline around A or B, set elevation to 0, add to new surface as only contour)

3) Make a new volume surface D = Surface C - Surface B

4) Make another volume surface E = Surface A - Surface D.

 

Since:

D = -B,

E = A-D = A -(-B)

hence E = A + B

 

Once I get Cad back in front of me i could work out way to invert Surface B in the surface settings w/o having to use Surface C (the flat plane) or Surface D, but that should be a quick workaround to resolve your original request and it will work in 3d

[viriato79]

First up, the diagrams aren't reading like its an addition of z values. As they are 2d graphs of X vs Z, row 1 overlapped on row 2 = same shape, not what is shown in row 3.

Then looking at row 3 -> 4, that also doesnt match up. But lets ignore that for now.

 

 

You are right, the hights of surface c are higher.

thanks

[Organic]

Hmm, that diagram has made me more confused as to what you are after.

[sinc]

 

1) Start with Surface A and Surface B

2) Make a new surface C at zero elevation. just a flat plane. (extract border from A or B or just draw polyline around A or B, set elevation to 0, add to new surface as only contour)

3) Make a new volume surface D = Surface C - Surface B

4) Make another volume surface E = Surface A - Surface D.

 

 

The problem with that approach is that C3D will not let you use a Volume Surface to create another Volume Surface.

[LukeT]

Sinc: good point. I didnt have access to CAD when I posted so was just going off memory.

 

In testing it now I am able to paste a volume surface into a normal surface.

 

So this leads to a somewhat inelegant solution, but it will get the job done:

- Start with Surface A & B

- Make surface C as flat plane at elevation 0.

- Make volume surface D = base "surface B" with comparison "surface C"

- Make surface E = paste "surface D" (E should be the reflection of B on z axis)

- Make final volume surface F = base "surface E" with comparison "A"

 

Alternatively, if the original surfaces are built from external point file data (like external CSV files), then a quicker way would be to make all the Z values negative for surface B in the CSV file.

Then you run a normal volume surface between surface A and B, since B is already flipped it will give the correct final output.

 

Neither solution is clean but it should get Viriato79's desired result.