Shading Algorithms & Techniques

1. Introduction

Shading is the process of assigning colors to pixels or vertices based on lighting conditions. It enhances realism by simulating how light interacts with surfaces.

• Improves visual realism
• Works with illumination models

2. Need for Shading

Without shading, objects appear flat and unrealistic. Shading provides depth cues and surface detail.

• Highlights curvature
• Shows light and shadow effects

3. Types of Shading

• Flat Shading
• Gouraud Shading
• Phong Shading

4. Flat Shading

Flat shading assigns a single color to an entire polygon by computing illumination once per face.

• Fast and simple
• Produces faceted appearance

5. Gouraud Shading

Gouraud shading computes lighting at polygon vertices and interpolates intensities across the surface.

• Smoother than flat shading
• May miss specular highlights

6. Phong Shading

Phong shading interpolates surface normals across the polygon and computes illumination at each pixel.

• High-quality smooth shading
• Accurate specular highlights

7. Comparison of Shading Techniques

Flat Shading        Gouraud Shading        Phong Shading
----------------   -------------------    -------------------
Per-polygon color  Vertex intensities     Per-pixel lighting
Fastest            Moderate speed         Computationally heavy
Faceted look       Smooth appearance      Very smooth & realistic

8. Advantages

• Improves realism of objects
• Supports smooth surfaces
• Flexible quality-performance tradeoff

9. Applications

• 3D games and animation
• CAD and modeling software
• Scientific visualization

Practice Questions

1. What is shading in computer graphics?
2. Explain flat shading.
3. Differentiate Gouraud and Phong shading.
4. Why is Phong shading more realistic?
5. Where are shading techniques used?

Practice Task