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

Masking Buffers

Before OpenGL writes data into the enabled color, depth, or stencil buffers, a masking operation is applied to the data, as specified with one of the following commands:

void glColorMask(GLboolean red, GLboolean green,                         GLboolean blue, GLboolean alpha);void glColorMaski(GLuint buffer, GLboolean red,                         GLboolean green, GLboolean blue,                         GLboolean alpha);void glDepthMask(GLboolean flag);void glStencilMask(GLboolean mask);void glStencilMaskSeparate(GLenum face, GLuint mask);

Sets the masks used to control writing into the indicated buffers.

If flag is GL_TRUE for glDepthMask(), the depth buffer is enabled for writing; otherwise, it’s disabled. The mask for glStencilMask() ...