--- title: 3D point classification slug: task-view-guide/odhK-3d-point-classification docTags: createdAt: 2026-04-30T13:19:19.454Z --- 3D point classification covers both **semantic** and **instance** segmentation. Each class is configured as either **semantic** (all points of that class share a single label) or **instance** (each painted region becomes its own object). When you annotate a 3D point classification task, there are 5 steps you need to master: ::::WorkflowBlock :::WorkflowBlockItem Understand what is moving and what is stationary ::: :::WorkflowBlockItem Annotate moving classes frame-by-frame, with aggregation off ::: :::WorkflowBlockItem Lock the finished moving classes before continuing ::: :::WorkflowBlockItem Turn aggregation on; annotate stationary instance classes, then semantic classes last ::: :::WorkflowBlockItem One class at a time, locking each class as you finish ::: :::: ## Understand the sequence first Scrub through the sequence before you start painting. Note which classes have moving objects (vehicles, pedestrians) and which are stationary (road, buildings, vegetation). This decides the order you work in and whether you use aggregation. ## Use prelabel boxes to start each class If the task includes 3D prelabel boxes, use them as the opener for any class whose objects are mostly captured by a box. Hover over an object, then press `R` (or `Shift+Click`) to classify all points inside the box in one action. This works for both semantic and instance classes. Move to the next frame and repeat the previous steps until you have annotated the moving object with prelabels throughout the sequence. ::::LinkArray{contentSource="CUSTOM" itemsPerRow="2"} :::LinkArrayItem Read more about how to classify points from 3D prelabel boxes in [Box classification tool](docId\:m8j33PuzyFeF6gzpz7IUk) ::: :::: ## Annotate moving objects first, aggregation off Aggregation smears moving objects across frames. Keep aggregation off (`Alt+A` toggles it) and annotate moving instance classes frame by frame. Work one class at a time — for instance, finish all cars before starting pedestrians. When you finish a class, lock it at the class level (`Alt+L`) so the next class you paint cannot overwrite it. ## Switch to aggregation for stationary work Once the moving classes are locked, turn aggregation on (`Alt+A`). The stationary parts of the scene now appear as a single, complete cloud, making it faster and more accurate to paint large surfaces (roads, buildings, vegetation). Annotate the stationary instance classes first, then the semantic classes. ## Drawing tools Pick the tool that fits the shape of what you are painting. Use `Shift+B` to cycle between the Cylinder brush, Sphere brush, Box classification tool, and Polygon classification tool. **The Cylinder brush** — for classifying large areas with broad strokes. **The Sphere brush** — for details and tight spaces. Works specifically well for annotating poles and other similar infrastructure. **[Box classification tool](docId\:m8j33PuzyFeF6gzpz7IUk)** — for vehicles and other objects that fit cleanly inside a box. **[Polygon classification tool](docId\:jHIVSYhtgqY8oz6D9K5mS)** — for large irregular regions; every point inside the polygon, visible from the current camera view, gets classified when you press `Enter`. **[Projection classification tool](docId\:QBm9vPK9YnWmymqsPUZjO)** — for classifying from a camera image; place **green** points on the object, `Alt+click` **red** points on occlusions, then press `Enter`. ## Other tools that help at each stage **Quick erase**. Press `Alt` while a drawing tool is active. This will temporarily activate the eraser. In other words, once you let go of the shortcut, you will return to drawing mode. For the Box and Polygon classifications tools, press `Alt+Enter` to erase. For the Cylinder and Sphere brush, press `Alt` while drawing to erase. **Eraser** (`N`). Erases whatever is under the brush, regardless of class — locking the classes you have finished prevents accidents. **[Point cloud slicing](docId\:gTV4dz53CZR-JKxl1l1LY)** (`Ctrl+scroll` to set the upper bound, `Ctrl+Shift+scroll` for the lower, `Alt+scroll` for fine adjustments, or select Window → Point cloud slicing... to open the dialog). Use it to isolate a height range, especially for road surfaces and small free-standing objects. **[Temporary region of interest](docId\:M33DLujifGB1UmfHyPpBH)**. Draw a polygon to hide everything outside it. Useful when two objects sit close together and are hard to separate by eye. It is a focusing aid, not a primary tool — keep using the standard drawing tools to do the actual painting. **Show/ hide selected** (`Shift+H`) and **Show/ hide selected object** (`Alt+Y`). Use these to declutter the view while you work on a specific class or instance. [Locate unlabelled areas](docId\:PjhfySmX9PnQW12XyNIOR). At the end of the task, hide the labeled points to reveal anything you missed. ## Common mistakes **Painting stationary classes with aggregation off** — you are only painting one frame's slice of the object; turn aggregation on (`Alt+A`) and paint the whole shape at once. **Painting moving objects with aggregation on** — aggregation smears moving objects; turn aggregation off and work frame-by-frame. **Skipping the class-level lock between classes** — without `Alt+L`, an erase or stray brush stroke can wipe points you already painted. **Using temporary region of interest as the main tool** — it scopes the view; the standard drawing tools should still do the painting. ## Related resources ::::LinkArray{contentSource="CUSTOM"} :::LinkArrayItem [3D point classification](docId\:PjhfySmX9PnQW12XyNIOR) ::: :::LinkArrayItem [Point slicing](docId\:gTV4dz53CZR-JKxl1l1LY) ::: :::LinkArrayItem [Temporary region of interest](docId\:M33DLujifGB1UmfHyPpBH) ::: ::::