A C++ 3D rendering engine based largely on LearnOpenGL that implements all basic 3D graphics techniques and whatever advanced features I want to implement.

History of lightning models, I plan to implement the ability to dynamically change this in a scene to visually illustrate the differences.

1. Flat Shading (1970s)

• Concept: The simplest shading model. Each polygon (triangle) is assigned a single color based on its normal and light source. No interpolation between vertices.
• Pros: Very fast and computationally cheap. Good for low-polygon models or stylized art.
• Cons: Hard edges between polygons make the object look faceted. No smooth transitions between light and shadow.
• Use Cases: Early 3D games. Low-poly aesthetics.

2. Gouraud Shading (1971 - Henri Gouraud)

• Concept: Interpolates lighting across vertices using linear interpolation. Calculates lighting only at each vertex, then interpolates colors across the triangle.
• Pros: Smoother appearance compared to flat shading. Still relatively fast.
• Cons: Specular highlights (shiny spots) are often missed because interpolation blurs them. Lighting accuracy depends on vertex density.
• Use Cases: Used in early real-time 3D games like PlayStation 1 and N64-era titles.

3. Phong Shading (1975 - Bui Tuong Phong)

• Concept: Interpolates normals across the surface instead of interpolating colors. Lighting is calculated per pixel rather than per vertex.
• Pros: Produces much smoother shading and more accurate specular highlights. Less dependent on polygon density.
• Cons: More computationally expensive than Gouraud shading. Still uses a simple empirical reflectance model.
• Use Cases: Many modern non-PBR real-time graphics, including OpenGL's built-in Phong lighting. Used in early 3D rendering like DirectX 8 games.

4. Blinn-Phong Shading (1977 - Jim Blinn)

• Concept: A modification of Phong shading to improve efficiency. Replaces the Phong specular calculation with the halfway vector (H = (L + V) / 2) instead of reflecting the light direction (R) and comparing with the view vector (V).
• Pros: Faster than Phong shading. Produces similar specular highlights.
• Cons: Still an empirical (non-physically based) model. Highlights look slightly different from Phong’s method.
• Use Cases: Became the standard for real-time graphics in the 2000s (DirectX 9, OpenGL fixed pipeline). Used in many older game engines before PBR became popular.

5. Cook-Torrance PBR (1982 - Robert Cook & Kenneth Torrance)

• Concept: Physically-Based Rendering (PBR): Simulates real-world light interactions. Uses microfacet theory: Surfaces consist of tiny reflective facets that scatter light. Key components: Bidirectional Reflectance Distribution Function (BRDF) Fresnel Effect (Schlick’s approximation) Microfacet Normal Distribution Function (NDF) Geometric Shadowing Function (G)
• Pros: More realistic than Blinn-Phong. Works well under different lighting conditions. Supports metallic and dielectric surfaces.
• Cons: More computationally expensive. Requires good asset creation (textures like roughness, metallic, AO maps).
• Use Cases: Became the standard for modern game engines (Unreal Engine, Unity HDRP). Used in films, high-end rendering, and modern graphics APIs (Vulkan, DirectX 12).