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Last update: April 27, 2021

How modifiers work in Blender, an overview

Modifiers is the key to getting a lot of modeling done in a very short amount of time in Blender. When you have grasped the basics of modeling in edit mode, it is time to learn about them.

Modifiers are calculations that procedurally change your object in Blender. You can manage them in the modifier tab found in the properties panel. Blender calculates modifiers one at a time from the top down and there are many modifiers available. A few to try could be the array, bevel and subdivision surface. Applying a modifier commits the calculation to the object. We should do this from the top down in most cases.

That is the short and compressed version. In the rest of this article, we will expand on this and learn more about how the modifier stack works. This is an overview and explanation of the stack rather than a step-by-step guide.

Let’s dive in!

What are modifiers in Blender?

When modeling in Blender we have two primary modes to work with. Edit mode and object mode. We do most of our modeling in edit mode using classic modeling tools such as extruding, loop cuts and bevels. This gives us a great control over what we create.

However, you will reach a point very early when you realize that regular modeling is limited. We can only do one thing at a time and the workflow is destructive, meaning that it's hard to move back and forth between stages during the modeling process.

This is where modifiers come in. Modifiers add a non-destructive workflow on top of the geometry we create in edit mode. It does not replace traditional modeling, instead it builds upon it.

We find modifiers in the properties panel. Go to the tab with the blue wrench icon. In this tab there is a single drop-down menu. If you click it, you will see all the modifiers in Blender that work with your selected object.

Different types of objects will have different modifiers. Many of them overlap and work the same for multiple types of objects, like curves, mesh objects or lattice object.

In this article we will focus on modifiers for mesh objects since these are the ones most likely useful to you.

There are four categories of modifiers for a mesh object.

  • Modify
  • Generate
  • Deform
  • Simulation

We will focus most of our attention on the generate and deform groups. But first, we will discuss the modifier stack.

How do Blenders modifier stack work?

We can add multiple modifiers. As they get added they appear below each other in the properties panel. We call this the modifier stack.

The order we add the modifiers is very important. Modifiers are calculated one after another. A modifier lower in the stack will do its modification on the state that the object is in once it is time for that modifier to do whatever it does.

It is much like when we model in edit mode. If we extrude first and then bevel the result may differ from beveling first and then extrude.

The lower a modifier is, the later its effect will be added to the object. This means that the lower modifiers also change the data previously changed or added by earlier modifiers.

We can move a modifier up and down the stack with its arrow buttons to change the order the stack is calculated.

Blender recalculates the stack in real time, or as fast as it can, depending on how large the changes are.

Where does the modifier stack live?

The modifier stack is an object mode thing. Generally, we don’t work with modifiers when we are in edit mode. Even if it is possible to do many operations on the modifier stack even there.

Inside an object we put different things. It can be a mesh, UV Maps, vertex groups and materials among other things. This is all data.

A modifier is in contrast, a mathematical formula that also lives inside the object. Inside the object data is put through the modifier stack, almost like a tunnel. As data travels through the tunnel it gets to each modifier in the stack until it reaches the end and it finishes all calculations.

What kind of modifiers do we have available in Blender?

Now that we got some understanding of the modifier stack, I will briefly explain what each group of modifiers does. Here they are again if you forgot.

  • Modify
  • Generate
  • Deform
  • Simulation

Let’s start with the important groups, generate and deform.

Modifiers can generate some new mesh

The generate group is made up of modifiers that add geometry to the object.

A good example of a generate modifier is the array modifier. This modifier adds copies of the object in a direction. Adding more geometry since it adds copies. But all the data still lives in the same object and we can change the settings in the modifier at any time.

Modifiers can also deform existing geometry

The deform group does not add mesh to the object. Instead, it deforms the existing geometry.

An example is the curve modifier. A curve modifier can have an object follow its path. If you combine it with an array modifier you can have the copies follow the curve.

Sometimes they modify other data than the mesh

The modify group does not affect the geometry of an object. Instead, it acts on some other data. It can be vertex groups, UV Maps or normals to name a few. This is the least used group and is geared to more advanced use.

Simulations are also part of the modifier stack

The simulation group is technically modifiers. They get added to the stack like any other modifier but their settings are in the physics tab. This is because each of the simulation types has extensive feature sets. After all, there are whole software packages built around certain physics engines alone.

One example is Marvelous Designer. A cloth simulation tool.

We will not cover simulations here since they can each make up several articles on their own.

Anatomy of a modifier in Blender

Modifiers can look very different, but there are some common landmarks to keep in mind.

All modifiers in Blender have a name. We can rename them to anything we want even if we in practice rarely care.

If the name background is red however, this means that the modifier does not have an effect. When this happens, it means that the modifier needs some settings before it can function as intended.

An example is a boolean or curve modifier, Both need an object as part of its internal function.

To the left of the name is an arrow where we can collapse the modifier so we don’t see the settings. Very useful when working with many modifiers to declutter the workspace.

On the right side we have a handful of buttons. This depends on the modifier. But at most, there are four buttons.

Camera icon - Enable or disable modifier when rendering
Monitor icon - Enable or disable modifier in the 3D viewport
Square icon - Enable modifier visibility in edit mode
Triangle icon - In edit mode, displays original geometry in its new position after the modifier has been calculated

Further to the right is an up and down arrow, this is where we rearrange the stack by moving modifiers up and down.

Then we have the X to delete a modifier.

Below this top row of buttons and the name are generally two or three buttons.

  • Apply
  • Apply as Shape key
  • Copy

We can copy a modifier with all the settings we made. The copy end up just below the modifier we copy.

We discuss “apply” and “apply as shape key” below, but for now we will skip them.

The rest of the modifier is made up of the settings that the specific modifier needs to function. These are the input fields. What we input in each setting for each modifier changes how they behave.

The result, or output, is then displayed in the 3D viewport or in the final render.

In this article I go into detail on 10 of the most commonly used modifiers.

Related content: Top 10 Blender modifiers and how they work

Let’s now look at what happens if we apply a modifier.

What happens when we apply a modifier?

If we hit apply on a modifier, the result, or output that it creates will be committed to the object. Geometry that is generated will be accessible in edit mode or sculpt mode.

Deformations will become permanent and we can’t change them through the modifier anymore.

The modifier will also be removed from the stack since it is now “baked” into the object as data rather than a formula.

This means we get access to the raw data that a modifier produces. But we also lose the control that the parameters on the modifier gives.

A very important thing to keep in mind is that we can only apply the modifier in the stack's top.

When we apply a modifier, it gets committed to data. This means that we can no longer depend on other modifiers above in the stack. We turn a modifier into data that run through the stack rather than being part of the stack.

Blender solves this potential issue by applying a modifier as if it is the first in the stack, even if it isn’t when we hit apply.

It also throws an information message in the status bar when this happens, telling us the result may not be what you expect.

With some modifiers, mostly in the deform category, we can “apply as shape key”.

Shape keys are different states of a mesh. You can find them by clicking the green triangle icon in the properties panel. Named the object data tab. There is a section called “Shape keys”.

You can read more about them in my basics to shape keys guide.

Related article: Blender shape key basics guide

When we apply to shape key the original mesh becomes the base state. Then another state, or key as we call them, is created that has the shape created by the modifier.

We can then interpret between the original state and the modified state.

We can use this to animate the shape key and create different effects.

We can also animate most fields on the modifier itself while it is in the stack. The benefit of a shape key is that we can export it to other applications.

The modifier stack is not supported in any other application.

If we need to apply the entire stack at once. Perhaps we have a large amount of modifiers in the stack. Then we can go to the object menu in the 3D viewport, find “Convert to” and select “Mesh from curve/meta/surf/Text”. Despite its name, this operation will apply all modifiers from the top down if used on a mesh object.

Final thoughts

The modifier stack can look very complicated at first. The best way to get a feel for it is to get some theory under your belt and then just dive in and try different modifiers and find out how they work.

So this is what I would encourage you to do now.

The good thing with Blender is that it is very hard to break. If it hangs, you just restart with a new scene and continue your exploration.

Keep it light and be fearless as you explore the world of 3D art.

Thanks for your time.

Written by: Erik Selin

Editor & Publisher

Erik Selin
3D artist, writer, and owner of artisticrender.com

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