8.6.2 Modeling Material Smoothness

As mentioned before, the apparent smoothness of a material is a function of how strongly it reflects and the size of the specular highlight. This is affected by the overall magnitude of the GL_AMBIENT, GL_DIFFUSE and GL_SPECULAR parameters, and the value of GL_SHININESS. Here are some heuristics that describe useful relationships between the magnitudes of these parameters:

1. The spectral color of the GL_AMBIENT and GL_DIFFUSE parameters should be the same.
2. The magnitudes of GL_DIFFUSE and GL_SPECULAR should sum to a value close to one. This helps prevent color value overflow.
3. The value of GL_SHININESS should increase as the magnitude of GL_SPECULAR approaches one.

No promise is made that these relationships, or the values in Table 3 will provide a perfect imitation of a given material. The empirical model used by OpenGL emphasizes performance, not physical exactness.

For an excellent description of material properties, see [31].

 

Material GL_AMBIENT GL_DIFFUSE GL_SPECULAR GL_SHININESS

Brass 0.329412 0.780392 0.992157 27.8974

0.223529 0.568627 0.941176

0.027451 0.113725 0.807843

1.0 1.0 1.0

Bronze 0.2125 0.714 0.393548 25.6

0.1275 0.4284 0.271906

0.054 0.18144 0.166721

1.0 1.0 1.0

Polished 0.25 0.4 0.774597 76.8

Bronze 0.148 0.2368 0.458561

0.06475 0.1036 0.200621

1.0 1.0 1.0

Chrome 0.25 0.4 0.774597 76.8

0.25 0.4 0.774597

0.25 0.4 0.774597

1.0 1.0 1.0

Copper 0.19125 0.7038 0.256777 12.8

0.0735 0.27048 0.137622

0.0225 0.0828 0.086014

1.0 1.0 1.0

Polished 0.2295 0.5508 0.580594 51.2

Copper 0.08825 0.2118 0.223257

0.0275 0.066 0.0695701

1.0 1.0 1.0

Gold 0.24725 0.75164 0.628281 51.2

0.1995 0.60648 0.555802

0.0745 0.22648 0.366065

1.0 1.0 1.0

Polished 0.24725 0.34615 0.797357 83.2

Gold 0.2245 0.3143 0.723991

0.0645 0.0903 0.208006

1.0 1.0 1.0

Pewter 0.105882 0.427451 0.333333 9.84615

0.058824 0.470588 0.333333

0.113725 0.541176 0.521569

1.0 1.0 1.0

 

Material GL_AMBIENT GL_DIFFUSE GL_SPECULAR GL_SHININESS

Silver 0.19225 0.50754 0.508273 51.2

0.19225 0.50754 0.508273

0.19225 0.50754 0.508273

1.0 1.0 1.0

Polished 0.23125 0.2775 0.773911 89.6

Silver 0.23125 0.2775 0.773911

0.23125 0.2775 0.773911

1.0 1.0 1.0

Emerald 0.0215 0.07568 0.633 76.8

0.1745 0.61424 0.727811

0.0215 0.07568 0.633

0.55 0.55 0.55

Jade 0.135 0.54 0.316228 12.8

0.2225 0.89 0.316228

0.1575 0.63 0.316228

0.95 0.95 0.95

Obsidian 0.05375 0.18275 0.332741 38.4

0.05 0.17 0.328634

0.06625 0.22525 0.346435

0.82 0.82 0.82

Pearl 0.25 1.0 0.296648 11.264

0.20725 0.829 0.296648

0.20725 0.829 0.296648

0.922 0.922 0.922

Ruby 0.1745 0.61424 0.727811 76.8

0.01175 0.04136 0.626959

0.01175 0.04136 0.626959

0.55 0.55 0.55

Turquoise 0.1 0.396 0.297254 12.8

0.18725 0.74151 0.30829

0.1745 0.69102 0.306678

0.8 0.8 0.8

Black 0.0 0.01 0.50 32

Plastic 0.0 0.01 0.50

0.0 0.01 0.50

1.0 1.0 1.0

Black 0.02 0.01 0.4 10

Rubber 0.02 0.01 0.4

0.02 0.01 0.4

1.0 1.0 1.0