The Decimate Modifier in Blender reduces dense meshes into simpler meshes. This improves performance and memory usage. It is a simple modifier and this guide will show you exactly how to use it in Blender.

What the Decimate Modifier Does

The decimate modifier takes the geometry of a mesh and reduces it by an amount that we define. It reduces the geometry in a way to minimize change to the overall shape of the object. This makes the object’s geometry less dense and more efficient.

In the following images, a photoscanned rock pile with 60,000 faces is reduced by 80% with minimal impact to the shape and detail of the model.

A dense photoscanned model with 60,000 faces in Blender's 3D viewport.
Rock pile with 60,000 faces
A photosanned pile of rocks decimated to 12,000 faces in Blender's 3D viewport.
Decimated rock pile with 12,000 faces

Adding the Decimate Modifier

To add a modifier in Blender, we select the object we want to add the modifier to.

Navigate to the modifier tab in the Properties Panel.

Choose “Add Modifier” and we find “Decimate” in the column labeled “Generate.”

When the Decimate modifier is added, it will appear in the Modifiers Stack.

Decimate Modifier Settings

The Decimate modifier’s controls are fairly simple. There are three methods of decimating the mesh:

Collapse: Collapses the edges. This is the default.

Un-Subdivide: Attempts to combine faces in the opposite manner of subdvision.

Planar: Consolidates only faces which are planar (adjacent and facing the same direction).

There is also an option to symmetrize the mesh when it is decimated and a setting to turn all faces into triangles (triangulate).

We can choose a vertex group of the object and the Decimate modifier will only affect geometry assigned to that vertex group.

Setting Decimate Ratio

The Decimate Ratio is the most important setting for the modifier.

The ratio is what percentage we want the mesh reduced to. In the below example is a mesh with about 60,000 faces (the modifier panel displays the object’s face count).

When the ratio is set to .2 it will remove 80% of the faces.

The decimate modifier set to ration 1.0 displays 59,760 faces in the modifier panel.
The decimate modifier set to ration 0.2 shows a face count of 12,205 in the modifier panel.

The resulting mesh looks like this…

Rock pile with 60,000 faces
Decimated rock pile with 12,000 faces

And here’s how the rendered object looks before and after the decimation.

Original object
Object decimated by 80%

Applying the Decimate Modifier

The Decimate modifier’s impact on the geometry can not be viewed in edit mode until the modifier is applied.

Once we apply the modifier, we will no longer be able to make changes to the modifier’s settings.

To apply the modifier, go to the controls in the modifier stack. Select the drop-down arrow next to the modifier’s name. Choose the first option for “Apply.”

The applied modifier will be removed from the stack and the mesh will now be permanently decimated.

More About Modifiers

To learn more about modifiers, see my Complete Guide to all 54 Blender Modifiers.

Here is a link to the Blender Manual page on the Decimate modifier.

Please have a look around my site and check out my YouTube channel for video tutorial. I love Blender and always enjoy sharing information on how to use it.

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