Calculating volume
-
Rich, I'm sure it could well be right. I got a similar figure when I did it in 2D outside of the 3D terrain. How did you calculate it?
-
@rich o brien said:
Would 741.527 Meters ³ be accurate?
You know that is the big disappointment of Sketchup, it has limited accuracy.
Tongue placed firmly in cheek.
Ken
-
-
That is the 'volume of excavation'...
However, 446.731 m³ is the 'volume of water' that the pond can hold.
To find this...
Make a 'unique' copy of the main form.
Add a large flat rectangle at the lowest point on the lip [i.e. the maximum water-level].
Intersect it with the main form to give the blob outline of the water-face.
Erase superfluous edges to leave just the blob 'water-face'.
Cut+Paste-in-place it into the main form's edit-context as the 'water' surface.
Now view it from the side [without perspective] and use select-by-fence + delete to remove the unneeded 'embanking' above the maximum water-level.
Orient all faces the same way.
The form is now a proper 'solid'.
In v8 the 'Entity Info' dialog returns its volume, in current units [here 'meters']... -
How do you know how high the water level is?
-
@rich o brien said:
How do you know how high the water level is?
If you make a flat plane [made outside of the form's context to avoid geometry stickiness] and move it up and down in the Z [blue] axis then there's a point which is at the lowest 'lip' - snap to that, constraining to axial movements with shift-key.
A lower position of the plane would mean the pond were not full.
A higher position of the plane means the pond would be 'over full' and therefore the water will run out until it was at this lowest 'lip' level.
So the maximum water level it always at this 'lowest lip' - i.e. that's the maximum volume of water the pond will hold.Your method returns the volume of excavation - the perimeter of the 'pond' is not level.
Your 'skinning' method is also at best an approximation of the excavation - because we don't know the original surface shape - if it were already concave then the real excavation would be less, if it had a mound over the pond's location then the real excavation could be a lot more !
If we had the original land-surface then intersecting and recombining the top[terrain] and bottom[pond] 'surfaces' into a single 'solid' would be straightforward, and it would then give the 'true volume of excavation' too...
The water-level volume is accurate as it uses only know excavation surfaces to intersect with... -
@rich o brien said:
I just used TGI3D Amorph to skin the loop and I had a solid
How many divers does it take to change a lightbulb?
Rich
I'll get right back to you. First I need to write the procedure then make the Sketckup illustrations. Rich how many decimal place accuracy do want.
Ken
-
TIG, thanks once again for coming up with the perfect answer. I have a deadline for the project today so that's very helpful.
Rich, thanks too for your suggestion. Whilst it is the volume of water I require it would still be useful to be able to work out the excavation volume with your method. I've downloaded Tgi 3D however I can't actually figure out how to skin the loop and get the solid. If you could point me in the right direction I'd be grateful.
-
Select the loop using Tgi Select tool while holding CTRL....
right click and choose Create Mesh
explode group and use Thomthom's Solid Inspector to find holes
-
Thanks Rich. The solid inspector is essential I've found when creating these sort of volumes.
Advertisement