Drag and Drop Files into Your Scene

Allow users to drag and drop 3D models (glTF, GLB, FBX, OBJ, USDZ, VRM) directly into your web experience with the DropListener component. Works in Unity and Blender.

Let users drag and drop 3D models directly into your web experience.

:::tip Works with Unity and Blender The DropListener component is available for both Unity and Blender integrations. :::

What You Can Do

• Drag Files - Users drag glTF, GLB, FBX, OBJ, USDZ, or VRM files into the browser

• Paste URLs - Users paste links to 3D models

• Auto-Place - Dropped objects appear where users drop them

• Auto-Scale - Make all dropped objects fit a consistent size

• Multiplayer - Share dropped files with other connected users

• Drop Zones - Only allow drops in specific areas

Quick Start

Basic Setup

In Unity or Blender:

1. Add a DropListener component to an object in your scene

2. Export and open in browser

3. Drag a 3D model file into the browser window

The model appears in your scene!

With Multiplayer

To share dropped files with other users:

1. Add a SyncedRoom component to your scene

2. Enable Use Networking on the DropListener

3. When someone drops a file, everyone sees it

Settings

Setting	What it does
Drop Area	Only accept drops on this specific mesh (leave empty for anywhere)
Fit Into Volume	Automatically resize dropped objects to fit a size
Fit Volume Size	The size to fit objects into (like 2×2×2)
Place At Hit Position	Drop objects where the cursor hits, or at a fixed spot
Use Networking	Share dropped files with other users

Examples

Product Viewer

Replace the current product when users drop a new model:

1. Add your initial product as a child of the DropListener object

2. When users drop a file, it replaces the current product

3. Enable Fit Into Volume so all products appear at the same size

Perfect for furniture configurators, product showcases, or avatar try-ons.

Designated Drop Zone

Only allow drops on a specific surface (like a table or platform):

1. Create a mesh object (cube, plane, etc.)

2. Add the DropListener to a different object

3. Assign the mesh to Drop Area

4. Files only work when dropped on that mesh

:::tip Needs a Mesh The Drop Area must have visible geometry for drag and drop detection to work. :::

Multiple Drop Zones

Create multiple independent drop zones, each with its own drop area:

How it works:

1. Create two cylinders (or any meshes) as separate drop areas

2. Create two DropListener components (can be on separate empty objects)

3. Assign the left cylinder to DropListener 1's Drop Area field

4. Assign the right cylinder to DropListener 2's Drop Area field

5. Each DropListener only responds to drops on its assigned cylinder

In the video above:

• Left cylinder: Drop area for DropListener 1 (displays the helmet)

• Right cylinder: Drop area for DropListener 2 (displays the camera)

• Each has its own independent drop zone

Why this is useful:

• Compare different models side-by-side

• Collaborative review tool - team members drop their designs to compare

• Create before/after comparisons

• Build product comparison tools

• Each drop zone can have different settings (fit size, placement, etc.)

• Multiple independent display areas

Example Setup:

• DropListener 1: Assigned to left cylinder, fits to volume 1×2×1

• DropListener 2: Assigned to right cylinder, fits to volume 2×2×2

• Drop different files on each cylinder to compare them side-by-side

Each cylinder acts as a completely independent drop zone with its own content.

Collaborative Scene Builder

Let multiple users add objects to a shared scene:

1. Add SyncedRoom to your scene

2. Enable Use Networking on DropListener

3. Disable Fit Into Volume if you want original sizes

4. Users can drag files and everyone sees them appear

Scripting

React to Drops

Run code when someone drops a file:

import { Behaviour, DropListener, DropListenerEvents } from "@needle-tools/engine";

export class MyComponent extends Behaviour {

    awake() {
        const dropListener = this.gameObject.getComponent(DropListener);

        // When a file is dropped
        dropListener.addEventListener(DropListenerEvents.FileDropped, (evt) => {
            const file = evt.detail as File;
            console.log("User dropped:", file.name);
        });

        // When an object is added to the scene
        dropListener.addEventListener(DropListenerEvents.ObjectAdded, (evt) => {
            const object = evt.detail.object;
            console.log("New object in scene:", object.name);

            // You can modify the object here
            // For example, add a glow effect or play a sound
        });
    }
}

Load from Code

Load a model without user interaction:

import { Behaviour, DropListener } from "@needle-tools/engine";

export class ModelLoader extends Behaviour {

    async start() {
        const dropListener = this.gameObject.getComponent(DropListener);

        // Load from URL
        const url = "https://example.com/model.glb";
        const object = await dropListener.loadFromURL(url);

        if (object) {
            console.log("Loaded:", object.name);
        }
    }
}

Special Features

Smart URL Handling

DropListener automatically handles special URLs:

• GitHub files - Paste GitHub URLs and they're converted to raw content

• Polyhaven models - Paste Polyhaven asset pages and get the 3D model

Placeholder Behavior

Child objects under the DropListener are treated as placeholders:

• They stay visible until the first drop

• They're automatically removed when a file is dropped

• Perfect for "Drop model here" preview objects

Common Questions

Can users drop multiple files? Currently one file at a time. If multiple files are dropped, only the first 3D model is loaded.

What about images? Images are automatically ignored. The DropListener only accepts 3D model formats.

How does multiplayer work? When enabled, dropped files are uploaded to Needle's server and the URL is shared with other users. They download and see the same object.

Does it work offline? Yes for local file drops. URL pasting and multiplayer require internet connection.

More Information

Live Example:

• DropListener Sample - Try it yourself with multiplayer

API Documentation:

• DropListener API - Complete technical reference

Related Guides:

• Networking & Multiplayer - Set up multiplayer features

• Loading Scenes - Load content dynamically