Intersect solid with surface and get volume of the rest of solid?


#1

Hello everybody,

I’m just thinking if there is any options how to create intersect solid with a surface?
For example I have terrain that has been created by function terrain from contours and want to cut off part of cylinder.
Could anybody helps me if it’s possible?

Thanks a lot for anything that could help.


#2

You want to learn how to use the Intersect Faces option.
You can intersect faces so that the geometry gets created where they touch so that you can then select and delete what you don’t want, or separate things.
Which version of intersect with that you use depends on how the faces interact. A simple way to put it, although not a full explanation, If they are in the same context you can select them and use ‘Intersect with selection’ and if they are separated by being in a group you can go inside the group and ‘Intersect the face with model’.
Here is a quick gif showing intersecting a face with a sphere that is a group.
So if you want the terrain to cut the cylinder and it is a solid group not loose geometry, you need to double click the group to edit then click the face to select it and right click for Intersect with model. This should give you line around the cylinder. You can then select the part you don’t want and delete it.


#3

Thanks alot! That could help and now I can do it.
So I have one more question if you could please help me again – is there any option how to get volume of rest of the object?


#4

I would help if you didn’t need to edit your question, rather that you had been more specific to begin with.

You need the cut cylinder to be a solid, so when you intersect it with the terrain you want the cylinder to cut the terrain too, therefore creating a cap for you cylinder.
Several ways to do it. Basically you want the cylinder and terrain in the same context when you intersect them. Whether that means using the raw geometry of both and making a hole in your terrain. Or using a copy of a section of the terrain pasted inside the cylinders group so that it’s non destructive to the original, depends on what you need.

It looks like the intersection is in the background on the terrain. If you can get that piece out and put it in place on the cut and it is a perfect fit it should form a solid and then you can read the volume in the Entity Info window.


#5

I’m very sorry for that :frowning: Maybe I have to create a brand new topic or not?

So if there is any more effectively way how to do it with solving volume problem I’ll very appreciate it. Until than I will try your description and move the cup to the top of the rest of cylinder…


#6

No I didn’t mean you need a new thread, I was just a bit frustrated that if your question had originally been as specific as it is now I would have given you a better slightly different answer. So it helps to be as clear as you can with your question.

For example I still don’t know if you mind having a hole in your terrain…

I’ll see if I can make a more appropriate gif when I have a sec.


#7

Here you go, this is it’s most basic form.
Make a copy of both parts, explode them so they are in the same context, in other words the faces are actually touching, intersect the faces with selection, then delete what you don’t want and make the parts you do want a group.
If all goes well and you don’t have tiny faces that cause holes you should have a solid group with a readable volume.
As I said, that’s the most basic form of intersect. You can do the same within groups and by copy pasting in place etc intersect with context and so on and so forth, but it’s all based on this process.
Tiny faces is a common problem. If your geometry is complex and small enough that you end up with line segments down around the 1mm range, faces can fail to form and you get holes.
The solution to this is scale your work up by 10 or 100 and scale down again when ready. Tiny faces can exist, but have problems being formed.


#8

Great, it works! Thanks a lot.
But you have right that is problem with more complex parts, for example this one:

I solve it with Volume Calculator plug-in but I’m not sure if there is a right volume when this plugin automatically computed some missing faces/lines that makes holes as you wrote.
So in the next time I will try scaling part to find holes and correct it manually if there isn’t any plug-in that can do the job for me (finding holes).

Anyway many thanks for helping me!