Phong Shading: Exploring the Depth of Visual Rendering: Phong Shading in Computer Vision

By Fouad Sabry

What is Phong Shading

In 3D computer graphics, Phong shading, Phong interpolation, or normal-vector interpolation shading is an interpolation technique for surface shading invented by computer graphics pioneer Bui Tuong Phong. Phong shading interpolates surface normals across rasterized polygons and computes pixel colors based on the interpolated normals and a reflection model. Phong shading may also refer to the specific combination of Phong interpolation and the Phong reflection model.

How you will benefit

(I) Insights, and validations about the following topics:

Chapter 1: Phong shading

Chapter 2: Gouraud shading

Chapter 3: Phong reflection model

Chapter 4: Shader

Chapter 5: Lightmap

Chapter 6: Reflection mapping

Chapter 7: Bui Tuong Phong

Chapter 8: Blinn-Phong reflection model

Chapter 9: Computer graphics lighting

Chapter 10: Vertex normal

(II) Answering the public top questions about phong shading.

(III) Real world examples for the usage of phong shading in many fields.

Who this book is for

Professionals, undergraduate and graduate students, enthusiasts, hobbyists, and those who want to go beyond basic knowledge or information for any kind of Phong Shading.

• Language: English
• Publisher: One Billion Knowledgeable
• Release date: May 5, 2024

Book preview

Chapter 1: Phong shading

Phong shading, or Phong interpolation, is an interpolation technique for surface shading in 3D computer graphics that was developed by computer graphics pioneer Bui Tuong Phong. Phong shading interpolates surface normals over rasterized polygons and calculates pixel colors in accordance with the interpolated normals and a reflection model. Phong shading can also refer to a particular combination of Phong interpolation and the Phong reflection model.

Bui Tuong Phong invented Phong shading and the Phong reflection model at the University of Utah and published them in his 1973 Ph.D. dissertation. At the time of their release, Phong's approaches were deemed revolutionary, but they have subsequently become the standard shading technique for many rendering applications. Due to their typically effective use of computing time per produced pixel, Phong's techniques have gained widespread acceptance.

Phong shading provides a more accurate approximation of the shading of a smooth surface than Gouraud shading. Phong shading presupposes a continuously fluctuating normal vector on the surface. When used to a reflection model with modest specular highlights, such as the Phong reflection model, the Phong interpolation approach outperforms Gouraud shading.

When specular highlights are located in the center of a huge polygon, Gouraud shading presents the most difficulty. Since these specular highlights are lacking from the polygon's vertices and Gouraud shading interpolates depending on the vertex colors, the inside of the polygon will lack the specular highlight. This issue is resolved with Phong shading.

In contrast to Gouraud shading, which interpolates colors across polygons, Phong shading linearly interpolates a normal vector from the polygon's vertex normals across the surface of the polygon. At each pixel, the surface normal is interpolated and normalized before being utilized in a reflection model, such as the Phong reflection model, to determine the final pixel color. Phong shading is more expensive computationally than Gouraud shading since the reflection model must be generated for each pixel rather than each vertex.

Variants of this approach are implemented with pixel or fragment shaders on modern graphics hardware.

Phong shading can also refer to the combination of Phong interpolation and the Phong reflection model, an empirical model of local illumination. It depicts the manner in which a surface reflects light as a combination of diffuse reflection and specular reflection. Based on the informal observation of Bui Tuong Phong, bright surfaces have small, intense specular highlights, whereas dull surfaces have large, less intense highlights. The reflection model also contains an ambient term to account for the scattered light in the overall scene.

{End Chapter 1}

Chapter 2: Gouraud shading

Gouraud shading, named after Henri Gouraud, is an interpolation technique employed in computer graphics to generate continuous shading of surfaces represented by polygon meshes. In practice, Gouraud shading is utilized most frequently to generate continuous lighting on triangle meshes by computing the illumination at the corners of each triangle and