Basic Concepts

Before starting to use MipMapEngine SDK, understanding some core concepts will help you use it better. This section introduces the basics of 3D reconstruction in an easy-to-understand way.

If you are a professional photogrammetry practitioner or want to directly understand API-related knowledge, you can skip this chapter and read: API Manual

🌍 What is 3D Reconstruction?

3D reconstruction is the process of creating 3D models from 2D images. Imagine you've taken multiple photos around a building, and 3D reconstruction technology can:

1. Analyze the relationships between these photos
2. Calculate the camera positions when the photos were taken
3. Calculate 3D information for corresponding pixels based on camera positions and textures
4. Express 3D geometric information of objects or scenes in the form of point clouds or meshes
5. Add textures to models based on photo textures to build realistic 3D models

3D Reconstruction Application Scenarios

• Surveying and Mapping: Generate high-precision topographic maps and orthophotos
• Urban Planning: Create 3D city models for planning and design
• Cultural Heritage Protection: Digitally preserve historical buildings and artifacts
• Emergency Response: Quickly obtain 3D information of disaster scenes
• Engineering Monitoring: Monitor construction progress and changes
• 3D Content Asset Generation: Generate 3D content assets for games, film, AR/VR

📸 Photogrammetry Basics

🔄 3D Reconstruction Workflow Details

🔄 ReconstructFull Basic Processing Workflow

Processing Workflow Features

• 🚀 Fully Automatic: Automatic processing from input to output, no manual intervention required
• 🎯 Intelligent Decision Making: Automatically selects optimal processing parameters based on data characteristics
• 📦 Multi-Format Output: Supports generating multiple formats simultaneously to meet different application needs
• ⚡ Parallel Optimization: Multiple output branches can be processed in parallel to improve efficiency

Output Selection Recommendations

• Web Display: Choose 3D Tiles + DOM tiles
• Professional Analysis: Choose OSGB + GeoTIFF + LAS
• Universal Exchange: Choose OBJ + PLY
• Surveying Applications: Choose GeoTIFF + DSM + Control point optimization

1. Aerotriangulation

AT is the first step of 3D reconstruction, its tasks are:

• Calculate the precise position and attitude of the camera when each photo was taken
• Establish geometric relationships between photos
• Generate sparse point cloud structure of the scene

2. Dense Reconstruction

After having camera positions:

• Calculate depth for each pixel
• Generate dense 3D point cloud

3. 3D Model Reconstruction

• Build 3D mesh models from point clouds
• Create model textures from original images
• Generate LOD models suitable for large-scale scene rendering

4. Generation of Different Format Results

Finally, generate different results according to your needs:

• 3D Models: OSGB, 3D Tiles, PLY, OBJ, FBX and other formats
• Point Cloud Data: LAS, PLY formats
• Gaussian Splatting Data: PLY, Splats formats
• Orthophotos: GeoTIFF format georeferenced images
• Digital Surface Model (DSM): Terrain elevation data

Standard Output Directory Structure

All reconstruction tasks generate the following standard outputs:

output/
├── 2D/
│   ├── dom_tiles/      # Orthophoto tiles
│   ├── dsm_tiles/      # Digital surface model tiles
│   └── geotiffs/       # GeoTIFF format results
├── 3D/
│   ├── model-b3dm/     # 3D Tiles model format
│   ├── model-osgb/     # OSGB model format
│   ├── model-ply/      # PLY model format
│   ├── model-obj/      # OBJ model format
│   ├── model-fbx/      # FBX model format
│   ├── point-ply/      # PLY point cloud format
│   ├── point-las/      # LAS point cloud format
│   ├── point-pnts/     # PNTS point cloud format
│   ├── point-gs-ply/   # PLY Gaussian Splatting format
│   └── point-gs-splats/# SPLATS Gaussian Splatting format
├── AT/
│   ├── mvs.xml         # AT results
│   └── mvs_undistort.xml # Undistorted AT results
├── report/
│   └── report.json     # Quality report
└── log.txt             # Processing log

Output Format Description

Format	Purpose	Features
3D Tiles	Web Display	Supports LOD, suitable for Cesium and other platforms
OSGB	Professional Software	OpenSceneGraph format, widely supported
OBJ	Universal Model	Simple and universal, easy to edit
LAS	Point Cloud Processing	Standard point cloud format, includes classification information
GeoTIFF	GIS Analysis	With geographic coordinates, can be used for measurement
Tiles	Online Maps	Multi-level tiles, fast loading

🎯 Key Parameter Explanations

Resolution Level

Controls the fineness of reconstruction:

Level	Description	Use Cases	Processing Time
1	Ultra-high precision, highest geometric detail and texture clarity	Professional surveying, fine modeling	Longer
2	High precision, some simplification of geometric details, highest texture clarity	General applications, quick results	Medium
3	Low precision	Preview, quick verification	Shorter

Image Overlap

🔍 Quality Control

Factors Affecting Reconstruction Quality

1. Image Quality

   • Clarity (avoid blur)
   • Lighting conditions (uniform lighting is best)

2. Shooting Parameters

   • Overlap (>70%)
   • Flight altitude (affects ground resolution)
   • Shooting angle (vertical + oblique combination is best)

3. Typical Control-Free Accuracy

   • RTK/PPK: Centimeter-level accuracy (12cm + 12*GSD)
   • Regular GPS: Meter-level accuracy

💡 Best Practices for Reconstruction Accuracy

• 🔧 Reliable Reconstruction Accuracy: RTK and PPK control-free solutions can achieve good accuracy most of the time, but control points and check points are still the most reliable accuracy guarantee and verification method. If your application requires 100% guarantee of accuracy goals, or if project delivery requires providing sufficient evidence to support the accuracy of results, be sure to set up control points/check points, otherwise you may face field data collection rework.

🚀 Next Steps

Now that you understand the core concepts, you can:

• Read the API documentation in detail, and customize your best automated workflow according to your business needs