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glRotate, glTranslate, and glScale are fundamental transformation functions in the OpenGL graphics library, used to manipulate the coordinate system and objects within a 3D scene. These functions are part of the OpenGL Fixed Function Pipeline and are used to apply transformations to vertices before they are processed by the vertex shader.

glRotate is used to rotate objects around a specified axis. It takes three parameters: the angle of rotation in degrees, and the x, y, and z components of the axis of rotation. The rotation is applied to the current transformation matrix, which is a 4x4 matrix that represents the current state of transformations.

glTranslate is used to translate (move) objects along the x, y, and z axes. It takes three parameters: the x, y, and z components of the translation vector. The translation is also applied to the current transformation matrix.

glScale is used to scale (resize) objects along the x, y, and z axes. It takes three parameters: the scaling factors for the x, y, and z axes. The scaling is applied to the current transformation matrix.

These functions are typically used in conjunction with each other to create complex transformations. For example, an object can be translated, rotated, and then scaled to achieve the desired position, orientation, and size in a 3D scene. It's important to note that the order in which these functions are called matters, as matrix multiplication is not commutative.

In modern OpenGL (version 3.0 and later), these functions are part of the legacy API and are not recommended for use. Instead, transformations are typically performed using vertex shaders, which provide more flexibility and control over the transformation process. However, understanding these functions is still important for working with legacy code and for understanding the basics of 3D graphics programming.