🧊 Java 3D Software Rasterizer

A from-scratch, CPU-based 3D rendering engine built in Java. This project implements the complete graphics pipeline manually—from parsing raw .obj data to calculating pixel-perfect triangles—without relying on GPU APIs like OpenGL or DirectX.

🌟 Key Features

• Custom 3D Pipeline: Complete implementation of Model-to-World and World-to-Screen transformations.
• Barycentric Rasterization: High-precision pixel filling that uses triangle area ratios for occupancy and depth interpolation.
• Dynamic Z-Buffering: A manual depth-buffer implementation to handle complex object overlapping and occlusion without the need for pre-sorting polygons.
• Optimized Memory Management: Uses a mutation-based approach for vertex transformations to minimize Garbage Collection overhead during high-frequency updates.
• OBJ File Parser: A custom-built parser to load 3D mesh data (vertices and faces) from standard .obj files.
• Interactive Camera & Transform: Real-time rotation and translation of 3D entities via keyboard input.

🕹️ Controls

Key	Action
UP / DOWN	Rotate object around X-axis
LEFT / RIGHT	Rotate object around Y-axis
W / S	Translate object along Y-axis
A / D	Translate object along X-axis

🛠️ Technical Breakdown

The Rasterization Loop

The TriangleDrawer uses a bounding-box approach for efficiency. For every triangle, the engine calculates the axis-aligned bounding box and iterates only through those pixels. For each pixel:

1. Inside-Outside Test: Checks if the pixel center lies within the triangle boundaries using perpendicular dot products.
2. Depth Interpolation: Uses the areas of sub-triangles (Barycentric coordinates) to find the exact $Z$ value of that pixel.
3. Z-Test: If the pixel is closer than the current value in the zBuffer, the pixels array is updated.

Mathematical Foundation

The engine relies on a custom math library (MathFuncs) for:

• Perpendicular Vectors: Used for edge detection during rasterization.
• Cross-Product Area: Efficiently calculates triangle areas to determine Barycentric weights.
• Rotation Matrices: Applied to vertices to simulate 3D movement.

🚀 Getting Started

Prerequisites

• Java 17+
• Raylib-Java: The project uses Raylib-J for window management and texture blitting.

Setup

1. Clone the repository.
2. Ensure raylib-java is in your project dependencies.
3. Update the model path in Main.java:

   o = ObjFileParser.converObjFileToRenderObject("C:\\YourPath\\model.obj");

4. Run Main.java.

📈 Future Improvements

• Perspective Projection: Implementing $W$-division for realistic "far-away" scaling.
• Flat Shading: Using face normals to calculate light intensity per triangle.
• 1D Z-Buffer: Refactoring the 2D depth array into a 1D array for better CPU cache locality.

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Developed as a deep-dive into the fundamentals of Computer Graphics.