GLZERO

GL_ZERO is an enumerant in the OpenGL graphics API used as a blending factor in color and alpha blending. In the blending stage, the final pixel color is formed by combining a source color and a destination color using factors that multiply each component of C_src and C_dst. GL_ZERO represents the numeric value zero, so when used as a blending factor it contributes no amount of the corresponding component.

As a source factor, GL_ZERO yields 0 * C_src, effectively removing the source color from the blend. As a destination factor, GL_ZERO yields 0 * C_dst, removing the destination contribution. This makes GL_ZERO useful for selectively enabling or disabling parts of the blending equation. For example, glBlendFunc(GL_ZERO, GL_ONE) leaves the destination color unchanged, while glBlendFunc(GL_ONE, GL_ZERO) replaces the destination with the source color.

GL_ZERO can also be used in glBlendFuncSeparate, where separate factors are specified for RGB and alpha channels. It is part of the OpenGL blending state and is defined as a symbolic constant in the GL headers, with an underlying value of zero.

In practice, GL_ZERO is most commonly discussed in the context of blending configurations that require precise control over which inputs affect the final color. While the fixed-function pipeline is considered legacy in modern OpenGL, the blending factors, including GL_ZERO, remain available in compatibility contexts and in shaders through equivalent blending state settings.