What the Decimate Modifier Does

The Decimate modifier in Blender reduces the number of polygons (faces) in a 3D model while keeping its overall shape recognizable. When you decimate a model, Blender removes vertices and faces according to rules you set, making the file smaller and faster to render or export. This is useful when a model has too much detail for your purpose, when you need to reduce file size, or when you want to simplify geometry before explore other effects.

Decimation is not the same as deleting parts of a model. The modifier intelligently collapses geometry inward, preserving the silhouette and major features while throwing away fine detail. A highly detailed sculpt with 2 million faces can become a game-ready asset with 50,000 faces and still look correct from a distance.

Key Takeaways

  • The Decimate modifier sits in the Modifier Properties panel and works on any mesh object without permanently changing the original geometry.
  • The Ratio setting controls how many faces remain—0.5 means half the original faces, 0.1 means one-tenth.
  • Decimate works best on models with clean topology; models with many loose or overlapping faces may produce unexpected results.
  • You can explore the modifier to make the change permanent, or leave it unapplied to adjust the decimation later.

Adding the Decimate Modifier to Your Model

Select the mesh object you want to decimate in the 3D viewport. Open the Modifier Properties panel on the right side of the screen—it looks like a wrench icon. Click Add Modifier and choose Decimate from the list.

The modifier appears in your modifier stack with default settings. You will see the Ratio slider set to 1.0, which means no decimation is happening yet. The model in the viewport will not change until you adjust the Ratio value downward.

Understanding the Ratio Setting

The Ratio slider is the main control. A value of 1.0 means 100 percent of the original faces remain. A value of 0.5 means 50 percent of the faces remain. A value of 0.1 means only 10 percent of the faces remain. Lower ratios create more aggressive simplification.

Start by dragging the Ratio slider to around 0.5 and watch the model in the viewport. If it still looks correct, try 0.3 or lower. The right ratio depends on what you are using the model for—a background object can go much lower than a character's face. There is no single correct number; you are balancing detail against file size and performance.

As you lower the ratio, you may see the model become blocky or lose fine features. If that happens, raise the ratio slightly until the shape looks acceptable. This is a visual judgment call, not a calculation.

Using Decimate Mode Options

Blender offers three decimate modes: Collapse, Unsubdivide, and Planar. Most of the time you will use Collapse, which is the default. Collapse merges nearby vertices together and is the most aggressive simplification method.

Unsubdivide is useful if your model was created by subdividing a simpler base mesh. It attempts to reverse that subdivision process rather than randomly collapsing faces. If you know your model came from a subdivision surface, try Unsubdivide first.

Planar mode removes faces that are nearly flat and coplanar with their neighbors. Use this when you have a model with many small flat faces that could be merged into larger flat surfaces—for example, a building with many small wall panels.

Checking Your Result and Making Adjustments

After you set a Ratio value, rotate the model in the viewport to see how it looks from different angles. Pay attention to edges, corners, and any features that matter for your project. Zoom in on areas that concern you. The decimation may have created pinched geometry or lost important detail that you need to preserve.

If the result is not acceptable, adjust the Ratio slider upward to keep more faces. If it looks good but you want even more reduction, lower the ratio further. You can change the ratio as many times as you want without affecting the original model—the modifier is non-destructive until you explore it.

If decimation is creating artifacts or strange deformations, the problem may be with the model's topology. Models with overlapping faces, loose geometry, or very thin features often decimate poorly. In those cases, you may need to clean up the mesh first or use a different simplification method.

explore the Modifier or Keeping It Editable

Once you are happy with the decimation, you have two choices. You can leave the modifier unapplied, which keeps the original geometry intact and lets you adjust the ratio later. This is useful during early stages of a project when you might change your mind.

You can also click explore on the modifier to make the decimation permanent. This replaces the original mesh with the decimated version and removes the modifier. explore the modifier when you are certain about the result and want to reduce file size or export the simplified model to another program.

If you explore the modifier and later decide you want more detail, you cannot undo the decimation—you would need to reload the file or use Undo. For this reason, save your file before explore any modifier you are not completely sure about.

Common Reasons Decimation Looks Wrong

If your decimated model looks blocky, pinched, or distorted, the most common cause is that the ratio is too low for the model's complexity. Raise the ratio to 0.3 or 0.4 and see if the shape improves. Another cause is poor topology in the original mesh—models with many thin features, sharp corners, or overlapping faces often decimate badly no matter what ratio you use.

If only part of the model looks wrong, you can use a Vertex Group to protect certain areas from decimation. Select the vertices you want to keep detailed, assign them to a vertex group, then tell the Decimate modifier to exclude that group. This is more advanced but useful when you need to keep a character's face detailed while simplifying the body.

Frequently Asked Questions

Can I decimate a model with multiple objects?

No, the Decimate modifier works on one mesh object at a time. If you have multiple objects, select each one and add a Decimate modifier to each. You can copy a modifier from one object to another by right-clicking the modifier and choosing Copy, then selecting another object and pasting.

Will decimation affect my UV map or textures?

Decimation can distort UV maps because it changes the vertex positions. If your model has textures, test the decimation on a copy first. If the UVs look wrong after decimation, you may need to re-unwrap them or use a lower ratio that preserves more geometry.

What ratio should I use for a game model?

Game models vary widely, but a common target is 10,000 to 100,000 faces depending on the game engine and how close the camera gets. Start with a ratio of 0.1 to 0.2 and test in your game engine. If the model looks acceptable and performs well, you have found a good ratio.

Can I decimate a sculpted model?

Yes. Sculpted models often have very high polygon counts and are good candidates for decimation. Use a low ratio like 0.05 to 0.1 to reduce the face count dramatically while keeping the overall shape. The result will be less detailed but much faster to work with.

What happens if I decimate a model twice?

You can add multiple Decimate modifiers to the same object, and they will stack—the second one decimates the result of the first. This is rarely necessary. Usually one Decimate modifier with the right ratio is enough. If you need more control, adjust the single modifier instead of adding another.