---
title: "Refine your mask before 3D — Segmentit"
description: "Refine a segmentation mask with inclusion points, exclusions and the eraser. Check edges and gaps before turning your photo into a 3D object."
lang: "en"
canonical: "https://segmentit.com/blog/refine-a-mask/"
---

# Refine your mask before 3D

Refine a segmentation mask with inclusion points, exclusions and the eraser. Check edges and gaps before turning your photo into a 3D object.

Segmentit team 2 min read

## Start with the subject

A segmentation mask separates the object you want to keep from the rest of the photograph. Check the entire silhouette: a piece of table can become part of the selection, while a missing handle removes useful visual information before reconstruction.

Click the object you want to isolate. Inspect the mask before converting: some background may have been included.

## Refine without restarting

Add points to recover missing parts. Use exclusion points to indicate areas outside the subject. Make small changes and check their effect.

## Check the details

Zoom into the Selection view. Inspect gaps between parts and erase remaining background. A clean mask does not guarantee the final geometry, but helps define what you want to reconstruct.

## Select part of an object

An automatic selection may identify a whole lamp when you only want its shade. Place a point on the part to keep and exclude neighbouring areas. If the result remains too broad, draw a manual outline to define the intended region, then inspect the Selection view.

Exclusion points guide segmentation; they do not erase individual pixels. For a small, precise fragment, use the eraser. Reduce its size near edges and undo a stroke if it removes useful detail.

## Which defects should you fix first?

| Visible issue | What to check |
| --- | --- |
| Background around the object | Remove detached fragments and surrounding scenery. |
| Missing parts | Inspect tips, legs, handles and antennas. |
| Filled gaps | Check inside handles and between separate elements. |
| Uneven edges | Compare with the photograph without erasing thin details. |

Before generating, return to an overall view. A carefully edited edge can look convincing up close while an important part is still missing. If the source is blurry or cropped, [take a better reference photo](https://segmentit.com/blog/photograph-an-object/) instead of accumulating corrections.

Continue with the [photo-to-3D guide](https://segmentit.com/blog/photo-to-3d/) and [inspect the resulting model](https://segmentit.com/blog/inspect-a-3d-model/). A mask describes a silhouette, not the object’s hidden surfaces.

[![A 3D car open in the Segmentit studio](https://segmentit.com/images/blog/studio-preview.png)](https://segmentit.com/app?lang=en) [Open the studio](https://segmentit.com/app?lang=en)