Duino/Duino-Lidar

Duino-Idar: An Interactive Indoor 3D Mapping System via Mobile Video with Semantic Enrichment

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Abstract

This paper introduces Duino-Idar, a novel end-to-end system for generating interactive 3D maps of indoor environments using mobile video. By leveraging state-of-the-art monocular depth estimation (via DPT-based models) alongside semantic understanding from a fine-tuned vision-language model (PaLiGemma), Duino-Idar provides a comprehensive solution for indoor scene reconstruction. The system extracts key frames from video input, computes depth maps, builds a 3D point cloud, and enriches it with semantic labels. A user-friendly Gradio-based GUI allows video upload, processing, and interactive exploration of the 3D scene. This research details the system's architecture, implementation, and potential applications in indoor navigation, augmented reality, and automated scene understanding, and outlines future improvements including LiDAR integration for enhanced accuracy.

Keywords:
3D Mapping, Indoor Reconstruction, Mobile Video, Depth Estimation, Semantic Segmentation, Vision-Language Models, DPT, PaLiGemma, Point Cloud, Gradio, Interactive Visualization

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1. Introduction

Advances in computer vision and deep learning have transformed 3D scene reconstruction from 2D images. With the ubiquity of mobile devices equipped with high-quality cameras, mobile video offers an accessible data source for spatial mapping. While monocular depth estimation techniques have matured for real-time applications, many 3D reconstruction approaches still lack semantic context—a critical component for applications such as augmented reality navigation, object recognition, and robotic scene understanding.

Duino-Idar addresses this gap by combining a robust depth estimation pipeline with a fine-tuned vision-language model, PaLiGemma, to enhance indoor 3D mapping. The name "Duino-Idar" reflects the fusion of user-friendly technology ("Duino") with advanced spatial sensing ("Idar"), hinting at future LiDAR integration while currently focusing on vision-based depth estimation. This paper presents the system architecture, implementation details, and potential use cases of Duino-Idar, demonstrating its contribution toward accessible and semantically enriched indoor mapping.

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2. Related Work

Our work builds upon three key research areas:

2.1 Monocular Depth Estimation

Monocular depth estimation forms the backbone of our geometric reconstruction. Pioneering works such as MiDaS [1] and DPT [2] have shown impressive capabilities in inferring depth from single images. In particular, DPT utilizes transformer architectures to capture global context, significantly enhancing depth accuracy compared to earlier CNN-based methods. The depth normalization process in DPT-like models is illustrated in Equation (1):

$$D=f(I;\theta )D\; =\; f(I;\; \backslash theta)$$

where ( D ) is the depth map estimated from the image ( I ) using model parameters ( \theta ).

2.2 3D Reconstruction Techniques

Reconstructing 3D point clouds or meshes from 2D inputs is a well-established field, encompassing methods from photogrammetry [3] and SLAM [4]. Duino-Idar leverages depth maps from the DPT model to create point clouds using the pinhole camera model. Equations (2)–(4) detail the transformation from 2D pixel coordinates to 3D space.

2.3 Vision-Language Models for Semantic Understanding

Vision-language models (VLMs) bridge visual data and textual descriptions. PaLiGemma [5] is a state-of-the-art multimodal model that integrates image interpretation with natural language processing. Fine-tuning on indoor scene datasets allows the model to generate meaningful semantic labels that are overlaid on the reconstructed 3D models.

2.4 Interactive 3D Visualization

Interactive visualization is key for effective 3D data exploration. Libraries such as Open3D [6] and Plotly [7] enable users to interact with 3D point clouds through rotation, zooming, and panning. Open3D is ideal for desktop-based exploration, while Plotly supports web-based interactive 3D visualizations.

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3. System Architecture: Duino-Idar Pipeline

3.1 Overview

The Duino-Idar system comprises three main modules, as depicted in Figure 1:

1. Video Processing and Frame Extraction:
   Ingests mobile video and extracts key frames at configurable intervals to capture scene changes while reducing redundancy.

2. Depth Estimation and 3D Reconstruction:
   Processes each extracted frame using a DPT-based depth estimator to generate depth maps. These maps are then converted into 3D point clouds via the pinhole camera model.

3. Semantic Enrichment and Visualization:
   Utilizes a fine-tuned PaLiGemma model to produce semantic annotations for each key frame, enriching the 3D reconstruction with object labels and scene descriptions. The Gradio-based GUI integrates these modules for an interactive user experience.

3.2 Detailed Pipeline

1. Input Module:

   • Video Upload: Users upload a mobile-recorded video via the Gradio interface.
   • Frame Extraction: OpenCV extracts frames at user-defined intervals, balancing detail with computational cost.

2. Depth Estimation Module:

   • Preprocessing: Frames are resized and normalized before being fed into the DPT model.

   • Depth Prediction: The DPT model generates a depth map for each frame.

   • Normalization and Scaling:
     The raw depth map is normalized and scaled for visualization:

     $$ D_{\text{norm}}(u,v) = \frac{D(u,v)}{\max_{(u,v)} D(u,v)} $$

     and, assuming a maximum depth ( Z_{\max} ):

     $$ z(u,v) = D_{\text{norm}}(u,v) \times Z_{\max} $$

3. 3D Reconstruction Module:

   • Point Cloud Generation:
     Using the pinhole camera model, each pixel is mapped to 3D space:

     $$ x = \frac{(u - c_x) \cdot z(u,v)}{f_x}, \quad y = \frac{(v - c_y) \cdot z(u,v)}{f_y}, \quad z = z(u,v) $$

     In matrix form:

     $$ \begin{pmatrix} x \ y \ z \end{pmatrix} = z(u,v) \cdot K^{-1} \begin{pmatrix} u \ v \ 1 \end{pmatrix} $$

   • Point Cloud Aggregation:
     Point clouds from multiple key frames are aggregated to form the final 3D model:

     $$ P = \bigcup_{i=1}^{M} P_i $$

4. Semantic Enhancement Module:

   • Vision-Language Processing:
     PaLiGemma processes key frames to generate scene descriptions and semantic labels.
   • Semantic Data Integration:
     These labels are overlaid on the point cloud to provide contextual scene information.

5. Visualization and User Interface Module:

   • Interactive 3D Viewer:
     The enriched 3D model is rendered using Open3D or Plotly, allowing interactive exploration.
   • Gradio GUI:
     A user-friendly web interface supports video upload, pipeline execution, and 3D scene visualization.

Figure 1: Duino-Idar System Architecture Diagram

Figure 1: The flow from mobile video input to interactive 3D visualization with semantic enrichment.

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4. Mathematical Foundations and Implementation Details

4.1 Mathematical Framework

1. Depth Estimation via Deep Network

Let ( I \in \mathbb{R}^{H \times W \times 3} ) be the input image. The DPT model ( f ) estimates the depth map ( D ):

$$D=f(I;\theta )\text{(1)}D\; =\; f(I;\; \backslash theta)\; \backslash quad\; \backslash text\{(1)\}$$

Normalize the depth map:

$$D_{\text{norm}}(u,v)=\frac{D(u,v)}{\underset{(u,v)}{\max }D(u,v)}\text{(2)}D\_\{\backslash text\{norm\}\}(u,v)\; =\; \backslash frac\{D(u,v)\}\{\backslash max\_\{(u,v)\}\; D(u,v)\}\; \backslash quad\; \backslash text\{(2)\}$$

Scale with maximum depth ( Z_{\max} ):

$$z(u,v)=D_{\text{norm}}(u,v)\times Z_{\max }\text{(3)}z(u,v)\; =\; D\_\{\backslash text\{norm\}\}(u,v)\; \backslash times\; Z\_\{\backslash max\}\; \backslash quad\; \backslash text\{(3)\}$$

For 8-bit scaling:

$$D_{\text{scaled}}(u,v)=\frac{D(u,v)}{\underset{(u,v)}{\max }D(u,v)}\times 255\text{(4)}D\_\{\backslash text\{scaled\}\}(u,v)\; =\; \backslash frac\{D(u,v)\}\{\backslash max\_\{(u,v)\}\; D(u,v)\}\; \backslash times\; 255\; \backslash quad\; \backslash text\{(4)\}$$

2. 3D Reconstruction using the Pinhole Camera Model

With intrinsic parameters ( f_x, f_y ) and principal point ( (c_x, c_y) ), the intrinsic matrix is:

Given pixel ( (u,v) ) and depth ( z(u,v) ), compute 3D coordinates:

$$x=\frac{(u-c_x)\cdot z(u,v)}{f_x},y=\frac{(v-c_y)\cdot z(u,v)}{f_y},z=z(u,v)\text{(6), (7), (8)}x\; =\; \backslash frac\{(u\; -\; c\_x)\; \backslash cdot\; z(u,v)\}\{f\_x\},\; \backslash quad\; y\; =\; \backslash frac\{(v\; -\; c\_y)\; \backslash cdot\; z(u,v)\}\{f\_y\},\; \backslash quad\; z\; =\; z(u,v)\; \backslash quad\; \backslash text\{(6),\; (7),\; (8)\}$$

Or in matrix form:

$$\left(\begin{array}{c}x\\ y\\ z\end{array}\right)=z(u,v)\cdot K^{-1}\left(\begin{array}{c}u\\ v\\ 1\end{array}\right)\text{(9)}\backslash begin\{pmatrix\}\; x\; \backslash \backslash \; y\; \backslash \backslash \; z\; \backslash end\{pmatrix\}\; =\; z(u,v)\; \backslash cdot\; K^\{-1\}\; \backslash begin\{pmatrix\}\; u\; \backslash \backslash \; v\; \backslash \backslash \; 1\; \backslash end\{pmatrix\}\; \backslash quad\; \backslash text\{(9)\}$$

3. Aggregation of Multiple Frames

For point cloud ( P_i ) from the ( i^\text{th} ) frame:

$$P=\bigcup _{i=1}^M{P}_i\text{(10)}P\; =\; \backslash bigcup\_\{i=1\}^\{M\}\; P\_i\; \backslash quad\; \backslash text\{(10)\}$$

4. Fine-Tuning PaLiGemma Loss

For an image ( I ) and caption tokens ( c = (c_1, c_2, \ldots, c_T) ), minimize the cross-entropy loss:

4.2 Implementation Environment and Dependencies

Duino-Idar is implemented in Python using the following libraries:

• Deep Learning: transformers, peft, bitsandbytes, torch, torchvision, and the DPT model.
• Computer Vision: opencv-python, Pillow
• 3D Visualization: open3d, plotly (for web deployments)
• GUI: gradio
• Data Manipulation: numpy

Install the dependencies using:

pip install transformers peft bitsandbytes gradio opencv-python pillow numpy torch torchvision torchaudio open3d

4.3 Code Snippets

4.3.1 Depth Estimation using DPT

import torch
from transformers import DPTFeatureExtractor, DPTForDepthEstimation
from PIL import Image
import numpy as np

dpt_model = DPTForDepthEstimation.from_pretrained("Intel/dpt-large")
feature_extractor = DPTFeatureExtractor.from_pretrained("Intel/dpt-large")

def estimate_depth(image):
    inputs = feature_extractor(images=image, return_tensors="pt")
    with torch.no_grad():
        depth_map = dpt_model(**inputs).predicted_depth.squeeze().numpy()
    depth_map = (depth_map / np.max(depth_map) * 255).astype(np.uint8)  # Normalize to 8-bit
    return depth_map

# Example usage:
image = Image.open("example_frame.jpg")  # Replace with an actual image path
depth_map = estimate_depth(image)

4.3.2 3D Point Cloud Reconstruction

import open3d as o3d
import numpy as np

def reconstruct_3d(depth_map, image):
    h, w = depth_map.shape
    fx = fy = max(h, w) / 2.0  # Approximate focal lengths
    cx, cy = w / 2.0, h / 2.0
    points = []
    colors = []
    image_np = np.array(image) / 255.0  # Normalize image

    for v in range(h):
        for u in range(w):
            z = depth_map[v, u] / 255.0 * 5.0  # Scale depth
            x = (u - cx) * z / fx
            y = (v - cy) * z / fy
            points.append([x, y, z])
            colors.append(image_np[v, u])  # RGB color from image

    pcd = o3d.geometry.PointCloud()
    pcd.points = o3d.utility.Vector3dVector(np.array(points))
    pcd.colors = o3d.utility.Vector3dVector(np.array(colors))
    return pcd

# Example usage:
point_cloud = reconstruct_3d(depth_map, image)
o3d.io.write_point_cloud("output.ply", point_cloud)

4.3.3 Gradio Interface for Interactive Visualization

import gradio as gr
import open3d as o3d

def visualize_3d_model(ply_file):
    pcd = o3d.io.read_point_cloud(ply_file)
    o3d.visualization.draw_geometries([pcd])

def extract_frames(video_path, interval=10):
    import cv2
    from PIL import Image
    cap = cv2.VideoCapture(video_path)
    frames = []
    i = 0
    while cap.isOpened():
        ret, frame = cap.read()
        if not ret:
            break
        if i % interval == 0:
            frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
            frames.append(Image.fromarray(frame))
        i += 1
    cap.release()
    return frames

def process_video(video_path):
    frames = extract_frames(video_path)
    depth_maps = [estimate_depth(frame) for frame in frames]
    final_pcd = None
    for frame, depth_map in zip(frames, depth_maps):
        pcd = reconstruct_3d(depth_map, frame)
        if final_pcd is None:
            final_pcd = pcd
        else:
            final_pcd += pcd
    o3d.io.write_point_cloud("output.ply", final_pcd)
    return "output.ply"

with gr.Blocks() as demo:
    gr.Markdown("### Duino-Idar 3D Mapping")
    video_input = gr.Video(label="Upload Video", type="filepath")
    process_btn = gr.Button("Process & Visualize")
    output_file = gr.File(label="Generated 3D Model (PLY)")

    process_btn.click(fn=process_video, inputs=video_input, outputs=output_file)

    view_btn = gr.Button("View 3D Model")
    view_btn.click(fn=visualize_3d_model, inputs=output_file, outputs=None)

demo.launch()

Figure 2: Conceptual Gradio Interface Screenshot
(Imagine a simple web interface with a video upload area, process button, and a section to view the generated 3D model.)

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5. Experimental Setup and Demonstration

Preliminary tests were conducted using mobile videos of indoor scenes (e.g., living rooms, kitchens, offices). Videos were uploaded via the Gradio interface, and the pipeline executed the following steps:

1. Frame Extraction: Key frames were extracted at a configurable interval.
2. Depth Estimation: The DPT model generated depth maps for each frame.
3. 3D Reconstruction: Depth maps were transformed into colored 3D point clouds.
4. Semantic Labeling: The PaLiGemma model provided semantic labels (e.g., "sofa," "table," "chair") which can later be integrated into the 3D scene.

Conceptual Graph: Depth Accuracy vs. Distance

Below is a text-based representation of the qualitative depth accuracy across different distances:

Depth Accuracy (Qualitative)
^
| Excellent
|     *
|    * *
|   *   *
| Good      *
|  *         *
| Moderate        *
+---------------------> Distance from Camera (meters)

For quantitative evaluation, metrics like RMSE or MAE can be used on ground-truth datasets.

Figure 3: Example 3D Point Cloud Visualization (Conceptual)
Imagine a sparse yet recognizable 3D point cloud representing an indoor scene.

Figure 4: Semantic Labeling Performance (Conceptual)

Replace the image link with an actual graph image URL to show performance per object category.

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6. Discussion and Future Work

Duino-Idar demonstrates a promising approach to accessible, semantically enriched indoor 3D mapping using mobile video. By integrating DPT-based depth estimation with a fine-tuned PaLiGemma for semantic context, the system provides both geometric and contextual scene understanding. The Gradio interface further democratizes access, enabling non-expert users to explore 3D reconstructions.

Future work will focus on:

• Enhanced Semantic Integration: Direct overlay of semantic labels onto the point cloud via segmentation techniques.
• Multi-Frame Fusion & SLAM: Incorporating robust SLAM methods to handle camera motion and improve reconstruction fidelity.
• LiDAR Integration: Combining LiDAR data with vision-based depth estimation for improved robustness.
• Real-Time Processing: Optimizing the pipeline (e.g., via TensorRT or mobile GPU acceleration) for near-real-time performance.
• Improved User Interaction: Enhancing the Gradio interface or integrating web-based 3D viewers (e.g., Three.js) for immersive interaction.
• Handling Dynamic Objects: Addressing the challenges of moving objects in indoor environments.

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7. Conclusion

Duino-Idar presents a novel and accessible system for indoor 3D mapping using mobile video, enriched with semantic context. By combining cutting-edge DPT depth estimation with a fine-tuned vision-language model, the system achieves robust geometric reconstruction and scene understanding. The user-friendly Gradio interface further lowers the barrier to entry. While this prototype lays a strong foundation, future iterations will enhance semantic integration, adopt advanced multi-frame fusion techniques, integrate LiDAR data, and target real-time performance improvements. These advances will expand Duino-Idar's applicability in fields such as augmented reality, robotics, and interior design.

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References

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