In legitimate rendering, the engine draws the world (walls, floors) first. Then it draws player models. But the Z-buffer already has values of "close" for walls. When a player model behind a wall tries to draw, the depth test fails: glDepthFunc(GL_LEQUAL) says, "Only draw if this pixel is closer than what's already there." Since it's behind, it doesn't draw.
Counter-Strike 1.6 , an "OpenGL Wallhack" typically refers to a modified opengl32.dll file that alters how the game renders textures.
The most common way to create an OpenGL hack is by making a proxy opengl32.dll . Since CS 1.6 looks for this file in its own directory first, you can place a custom version there.
Disables the visual effects of flashbangs and smoke grenades by blocking specific rendering calls. Lambert (Bright Models):