🌌 Unity Compute Shader Raytracing Lab

A beginner-friendly Unity raytracing playground built with compute shaders, mathematical spheres, GPU buffers, and Scene View visualizers.

This project is inspired by Sebastian Lague's wonderful video Coding Adventure: Ray Tracing. I am using it as a learning lab to rebuild the core ideas step by step inside Unity: camera rays, ray-sphere intersections, materials, emission, and eventually path tracing.

📸 Screenshots

First raytraced view	World coordinates

Ray visualization	Material application

✨ What It Does

• Shoots one ray per pixel from the active Unity camera
• Uses a compute shader to render into a RenderTexture
• Uploads Unity sphere data to the GPU with a ComputeBuffer
• Intersects rays with mathematical spheres instead of mesh triangles
• Supports per-sphere material properties:
  • base color
  • emission color
  • emission strength
  • roughness
• Shows the result in Game View and Scene View
• Includes a fly camera controller using Unity's Input System
• Includes educational visualizer scripts for raytracing concepts

🧠 Concepts Learned

This project helped me learn:

• how pixels become world-space rays
• how camera matrices are passed to compute shaders
• how ray-sphere collision works with the quadratic formula
• how to store closest-hit data in a hitInfo struct
• how Unity C# structs must match HLSL buffer layout
• why GPU data is usually packed in groups of four floats
• how material data can travel from the Inspector to the GPU
• how emission is added to a raytraced color
• how editor lifecycle bugs happen with ComputeBuffer and RenderTexture
• how Scene View image effects work with [ExecuteAlways]

More detail: docs/CONCEPTS.md

🕹️ Controls

Attach cameracontroll to the camera.

Input	Action
WASD	Move
Space	Move up
Left Ctrl	Move down
Left Shift	Sprint
Hold right mouse	Look around

🗂️ Project Layout

Assets/
  attempt1/
    customtracer.compute        # Current compute raytracer
    RaytracingSphere.cs         # Sphere data + material properties
    cameracontroll.cs           # Fly camera controller

  basics/
    shadermanager.cs            # Camera effect, GPU upload, dispatch
    ComputeBlend.shader         # Blends compute texture to camera output
    *Visualizer.cs              # Scene View learning helpers

  Scenes/
    hellowworld.unity
    SampleScene.unity

docs/
  CONCEPTS.md
  README.md
  tutorials/
    unity-compute-shader-raytracing.md
  images/
    paste screenshots here

🚀 Getting Started

1. Open the project in Unity 6000.0.23f1 or a compatible Unity 6 editor.
2. Open Assets/Scenes/hellowworld.unity or Assets/Scenes/SampleScene.unity.
3. Select the camera.
4. On shadermanager, assign:
   • testingshader -> Assets/attempt1/customtracer.compute
   • blendMaterial -> the compute blend material
   • Spheres -> any GameObjects with RaytracingSphere
5. Add RaytracingSphere to Unity sphere GameObjects.
6. Change color and emission values from the Inspector.
7. Press Play or enable Scene View shader preview.

📖 Tutorial

There is one cleaned-up tutorial now:

👉 Unity Compute Shader Raytracing Tutorial

Older AI-generated tutorial drafts were removed from the active docs because they repeated themselves and drifted away from the current code.

🔬 How The Renderer Works

The render loop is:

Camera renders
    ↓
shadermanager gathers sphere data
    ↓
ComputeBuffer uploads spheres/materials
    ↓
customtracer.compute traces rays
    ↓
Result texture is blended back to camera

The GPU sphere layout is packed as:

position.xyz + radius
color.rgb + emissionStrength
emissionColor.rgb + roughness

That is 12 floats per sphere, so the C# buffer stride is:

sizeof(float) * 12

🛠️ Current Status

Implemented:

• camera rays
• analytic sphere intersections
• closest-hit tracking
• material upload
• emission color
• Scene View preview
• fly camera movement
• educational gizmo visualizers

Next ideas:

• sky gradient
• emissive light spheres
• shadows
• diffuse bounce rays
• accumulation over frames
• rough reflections
• Cornell box scene

🙏 Credit

Inspired by Sebastian Lague's Coding Adventure: Ray Tracing. His video made the raytracing concepts feel approachable, and this repo is my Unity-based learning version of those ideas.