🚗 Connected Cars Simulation on OpenStreetMap (Qt6)

A high-performance C++ simulation built with Qt 6 that parses OpenStreetMap (OSM) data to simulate an urban environment where connected vehicles interact in real-time.

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📸 Project Gallery

City Infrastructure	Connected Vehicle Logic
Rendering of OSM ways and nodes	V2V connection via frequency proximity

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🚀 The Engineering Journey (Optimization)

The core challenge of this project was rendering complex geographic data while maintaining a high frame rate for car movements.

1. The Bottleneck: QWidget & PaintEvents

Initially, I used a standard QWidget and overloaded the paintEvent. This proved inefficient because any movement required a full screen refresh, causing significant lag even with small .osm files.

2. Data Strategy: MySQL Integration

Parsing large XML files on every launch was slow. I implemented a Database-First approach:

• Parsing: .osm files (Nodes, Ways, Tags) are parsed once and stored in a MySQL database.
• Retrieval: The app queries QSql tables for faster data access during rendering.

3. Rendering: QGraphicsView Framework

To optimize the UI, I migrated to the QGraphicsView and QGraphicsScene framework. Unlike the paint event, this framework only redraws modified elements (the moving cars), leaving the static city map cached in the background.

4. Concurrency: Multithreaded Drawing

To display an entire city without freezing the UI, I utilized Qt Concurrency. Roads (Ways) are drawn independently in parallel, using QApplication::processEvents() to keep the interface responsive during the initial load.

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🛠️ Core Features

• V2V Connectivity: Each car is assigned a random frequency. A visual circle represents the signal range; when two cars' circles overlap, they are marked as "Connected."
• Geospatial Mapping: A BoundsCalculator translates real-world Latitude and Longitude into optimized screen coordinates.
• Network Grids: A hexagonal grid system (Maille) is overlaid to represent network coverage areas.
• Traffic Logic: Cars follow specific road "Ways" and respect speed limit tags extracted from the OSM data.

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📂 Class Architecture

Class	Description
ConfigManager	Manages screen scaling and window dimensions.
Car	Logic for movement, speed limits, and connectivity range.
DatabaseManager	Handles MySQL connections and initial OSM XML parsing.
CustomScene/View	Custom rendering engine for the optimized GraphicsView.
BoundsCalculator	Normalizes GPS coordinates to local pixel coordinates.
Maille	Generates the hexagonal network grid logic.
Node / Way	Object representations of OpenStreetMap elements.

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🏗️ Build Instructions

Prerequisites

• Qt 6 (Core, Sql, Gui, Widgets)
• MySQL Server
• CMake 3.28+

Compilation

mkdir build && cd build
cmake ..
make
./GraphicsInQt