glClearGLDEPTHBUFFERBIT

glClear is an OpenGL function used to reset the contents of the currently bound framebuffer’s buffers. It takes a bitwise OR of buffer mask constants such as GL_COLOR_BUFFER_BIT, GL_DEPTH_BUFFER_BIT, GL_STENCIL_BUFFER_BIT, and GL_ACCUM_BUFFER_BIT. The buffers cleared are reset to their current clear values, which are set with glClearColor for color buffers, glClearDepth or glClearDepthf for the depth buffer, and glClearStencil for the stencil buffer. Clearing is affected by the current write masks and by the scissor test and viewport state.

To clear the depth buffer, the GL_DEPTH_BUFFER_BIT mask is used. The depth value written during the clear is determined by the depth clear value, which can be set with glClearDepth or glClearDepthf (the latter uses a floating-point value in [0,1]). The default depth clear value is 1.0, corresponding to the far plane. After enabling depth testing, clearing to 1.0 helps ensure that subsequent fragments can be properly compared against existing depth values.

There is no function named glClearGLDEPTH; the correct approach is to call glClear with GL_DEPTH_BUFFER_BIT, optionally along with other buffers, for example glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT). A typical sequence is to set the desired clear color and depth, then clear at the start of a frame, such as glClearColor(0.0f, 0.0f, 0.0f, 1.0f); glClearDepthf(1.0f); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT). For more advanced use, glClearBufferfv and related functions can clear specific attachments of a framebuffer object.