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OpenGL 2D Blackhole Simulator

Build a 2D gravitational lensing simulator with OpenGL. Visualize light ray bending around a black hole using the Schwarzschild metric and numerical integration.

~4 hours

13 steps

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What You'll Build

An interactive 2D visualization showing light ray trajectories bending around a black hole. Watch as rays with different impact parameters either escape to infinity or spiral into the event horizon, demonstrating gravitational lensing in real-time.

Learning Objectives

Set up OpenGL development environment
Implement 2D rendering with OpenGL
Understand the Schwarzschild metric
Implement Runge-Kutta 4th order numerical integration
Visualize gravitational lensing in 2D

Ready to Start?

Project Steps

Step 1

OpenGL Setup - Part 1: CMake Configuration

Configure CMake to find and link OpenGL, GLFW, GLEW, and GLM libraries.

~20 min

Step 2

OpenGL Setup - Part 2: Window Creation

Create a GLFW window and initialize OpenGL context for 2D rendering.

~15 min

Step 3

OpenGL Setup - Part 3: Render Loop

Create the main render loop to keep the window responsive and ready for drawing.

~20 min

Step 4

2D Rendering - Part 1: Coordinate Systems

Set up a 2D coordinate system using orthographic projection to map world coordinates to screen pixels.

~20 min

Step 5

2D Rendering - Part 2: Filled Shapes

Learn to draw filled circles using trigonometry and GL_TRIANGLE_FAN for efficient rendering.

~20 min

Step 6

2D Rendering - Part 3: Outlines and Styling

Draw circle outlines with GL_LINE_LOOP and style shapes using colors and line widths.

~15 min

Step 7

2D Rendering - Part 4: Aspect Ratio Correction

Fix circle distortion by adjusting orthographic projection to match the window's aspect ratio.

~15 min

Step 8

Schwarzschild Physics - Part 1: Metric Basics

Implement the Schwarzschild metric and understand conserved quantities for light rays in curved spacetime.

~30 min

Step 9

Schwarzschild Physics - Part 2: RK4 Integration

Implement Runge-Kutta 4th order integration to trace light ray paths through curved spacetime.

~40 min

Step 10

Visualization - Part 1: Ray Paths

Draw light ray paths showing gravitational lensing using OpenGL lines.

~40 min

Step 11

Visualization - Part 2: Visual Enhancements

Add professional visual touches: background stars, photon sphere visualization, event horizon circle, and color-coded light rays.

~40 min

Step 12

Visualization - Part 3: Multiple Ray Scenarios

Implement three distinct ray scenarios (parallel, point source, and orbiting) with ~100 total rays to create a comprehensive, visually stunning gravitational lensing demonstration.

~22 min

Step 13

Project Organization

Refactor the single-file simulator into a well-organized multi-file C++ project with proper separation of concerns

~120 min

Local Setup Required

This advanced project requires external libraries and will compile code that you download and run locally.

Required Dependencies:

opengl glfw glew glm

Want to Know More?

Read the full write-up about this project and support our work on Patreon.

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Project Repository

See the final version of this project on GitHub. Please report any issues there.

View on GitHub