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I am self-experimenting with the boolean operation. I took one box and put one sphere, a rotated box, and a cone on it. Then I wanted to see if I can apply Difference on all of them.

But as I move into the third object (cone) to apply the boolean, the second object (rotated box) undo the boolean operation itself. Why?

Does that mean I can apply a boolean only on two objects? Not three?

enter image description here

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    $\begingroup$ What exactly are you doing there? First of all, applying a modifier (which you can do by hovering over it and pressing Ctrl+A or choosing Apply from its menu) is not just using a modifier - it's applying the change permantly (destructively) to the mesh and removing the modifier. The cutout of the sphere seems to be applied earlier, because it's there although there is no Boolean modifier visible on the object at first. What you show then is just giving it a new modifier and switching the object which should be cut into the other. Only the object shown in the field is cut from the base. $\endgroup$ Nov 24, 2022 at 18:26
  • $\begingroup$ Now you can either apply it to have a permanent cutout, then use a new modifier for the next object and so on. Or if you don't want to make the cut permanent and keep the modifier you have to either use multiple modifiers (for each object its own) or set the Operand Type to Collection, in this case you can choose a collection of objects which are then used to cut the base mesh. Last option would be, if you want to use a single object, to join all objects that you want to use as cutter into a single one by selecting them and pressing Ctrl+J to join them. $\endgroup$ Nov 24, 2022 at 18:30
  • $\begingroup$ Hello, I was experimenting (facepalm). I wanna subtract all those three which were overlapping with the box. using Boolean. I was watching one tutorial on youtube there the teacher can subtract two objects from one. but he duplicate those two $\endgroup$ Nov 24, 2022 at 19:16
  • $\begingroup$ youtube.com/watch?v=RDKt_lNAHss $\endgroup$ Nov 24, 2022 at 19:16
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    $\begingroup$ @RussianBlue Then please watch the tutorial carefully. Jay subtracts two objects and uses two modifiers for that - one for each object. So if you want to subtract three, use three modifiers. And this is an old tutorial, the Boolean modifier he uses has different options then yours. For example, as I said you can put three objects in a collection and then use Operand Type > Collection to subtract all three with one modifier. This option wasn't available at the time when this tutorial was made. $\endgroup$ Nov 24, 2022 at 19:34

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I think @GordonBrinkmann already explained it well but just in case, I wanted to point out what are the errors you have done and also some terminology mistakes that I really want to mention because they kind of gave me a hard time understanding the problem and what you wanted to do. Please don't have any hard feelings for this, this is a forum and I am just trying to be as helpful as I can be.

The first thing I had trouble to understand was that you wanted to apply difference on 3 objects. I understood later (after watching the youtube video) that you meant apply a difference on the Cube using the 3 obects as difference objects. The correct thing to say here is apply difference on the cube (since the cube is the only one object that will receive a Boolean modifier).

The next thing you may want to know is how the Boolean modifier (and more generally Blender's modifiers) actually works.

Blender's modifiers are non-destructive. That means, when you give a modifier to an object, the modifier's effects are visible but not permanently applied to the mesh. This allows the user to change the parameters of the modifier or even turning its visibility OFF/ON without having to undo with CTRLZ. Each modifier, though, has an Apply function that allows you to make its effect permanent and removes the modifier from the modifier stack.

It's the same thing for Boolean modifiers. If, for example, you add a Boolean modifier to a cube and set the difference object as a cone, you will see the changes made to the cube in realtime. If you change the boolean object to another one without applying the modifier, the cone will not have any effect on the cube anymore (that's what happened in the screenshot you posted). in the tutorial, Jay applied the modifier before adding another modifier and choosing the next object as a difference object.

Long story short, there are 3 ways to do what you want to do (the 3rd way is, as stated by @GordonBrinkmann, only possible for Blender 2.8 and later).

1st METHOD - apply Boolean 3 times

This is the method shown in the tutorial. Add a Boolean modifier to the cube, choose the difference object, apply the modifier and repeat that step using the next object as difference object, apply the modifier again and add another modifier for the last object.

This method will work for as many objects as you want (just remember to apply the modifier each time) but it's a destructive method, meaning you will not be able to go back and tweak the results after you have applied the modifiers, so most of the people here would recommend using one of the two other methods instead.

2nd METHOD - use 3 Boolean modifiers at the same time

It's the non-destructive version of the 1st method. You probably know that already but you can use multiple Boolean modifiers to an object. So instead of applying the first modifier, you just leave it there, add two other ones set to difference and set the difference objects as the remaining two objects in your scene (in your case, it's the cube and the cone). Your modifier stack will then look like this :

modifier stack with 3 boolean modifiers

It gives the same result as the 1st method with the added advantage that you can still change the modifiers' parameters or even modify the difference objects while seeing the effects of the modifiers update in real time.

3rd METHOD - use a collection

Since the introduction of Collections in Blender 2.8, the Boolean modifier had an extra option called Operand Type which allows to choose an Object or a Collection as an Operand. So if you change the Operand Type to Collection, you can choose an entire collection instead of just one object.

Select the 3 objects and press M and choose New Collection,

Move to Collection

type a name for the new collection.

Collection name

Select your Cube, add a Boolean modifier to it, set the Operand Type to Collection and choose the new collection you created :

The modifier

As the 2nd method, it is also non-destructive but this time you only have 1 modifier in your modifier stack and if you need to add/remove a difference object, you just add/remove it to/from the collection.


Obviously, the 3rd method is the best one since it allows you to non-destructively add as many Operand objects as you want without oversaturating your modifier stack.

Sorry for the (very) long answer. I hope I still helped in some way.

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  • $\begingroup$ Good explanation. I had no time for an excessive answer, but it's good you described the different methods in more detail. By the way, Jay actually uses the 2nd method in the video, but the OP didn't pay attention to that. That's why I always say when people have problems getting the same result as a tutorial, they should watch it thoroughly and make sure they are doing the same as shown there. But anyway, at first I had problems understanding what the question is, too. $\endgroup$ Nov 25, 2022 at 13:47
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    $\begingroup$ Yep. Sometimes, it's because they skip directly to the part they are interested in, disregarding the prior setups that the tutorial maker took. $\endgroup$ Nov 25, 2022 at 13:57
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    $\begingroup$ Thanks for the edit by the way. $\endgroup$ Nov 25, 2022 at 13:57
  • $\begingroup$ The one limitation of the 3rd option is that you cannot use one object to subtract from many others. For example, it works well if you want to remove the cube, sphere, and pyramid from the large block. But what if I want to use the large block to slice the cube, sphere, and pyramid along the same plane? You will still have to put a modifier on each one of the cube, sphere, and pyramid pieces. $\endgroup$
    – Matt
    Jan 31 at 21:36
  • $\begingroup$ HOWEVER, there is a (new?) alternative to the "ctrl-L" method of linking modifiers. The problem with linking modifiers with ctrl-L is that it will REPLACE any modifiers already on the target objects. BUT if you select all of the objects that you want to have the boolean modifier, then you can click on the little arrow on the boolean modifier (between the "remove" X and the visibility toggles) and choose "Copy to selected..." and it will copy the one boolean modifier to all the other objects you have selected WITHOUT replacing the modifiers they already have. $\endgroup$
    – Matt
    Jan 31 at 21:41

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