OpenGL Programming Guide: The Official Guide to Learning OpenGL, Version 4.3, Eighth Edition

Granite

With noise, it’s also easy just to try to make stuff up. In this example, we want to simulate a grayish rocky material with small black specks. To generate a relatively high-frequency noise texture, we use only the fourth component (the highest frequency one). We scale it by an arbitrary amount to provide an appropriate intensity level and then use this value for each of the red, green, and blue components. The shader in Example 8.20 generates an appearance similar to granite, as shown in Figure 8.27.

Example 8.20. Granite Fragment Shader

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#version 330 coreuniform sampler3D Noise;uniform float NoiseScale;in float LightIntensity;in vec3  MCposition;out vec4 FragColor;void main(){   vec4 noisevec   = texture(Noise, ...