glBlendFuncSeparateGLSRCALPHA

The glBlendFuncSeparate command is an OpenGL primitive used to specify blending equations for the RGB and alpha components independently. It replaces the earlier single‑parameter blending call glBlendFunc when finer control over the alpha channel is required. The function takes four arguments: srcRGB, dstRGB, srcAlpha, and dstAlpha. Each of these is an enum specifying a blending factor such as GL_ONE, GL_ZERO, GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, and so on. The two first parameters control how the source and destination color values are weighted during color blending, while the last two parameters apply to the alpha component.

The separate calling mechanism became standardized in the OpenGL 2.0 core profile and is widely supported in modern desktop and mobile graphics drivers. It allows for complex compositing operations where the alpha channel may need to be modified differently from the color channels—for example, when creating premultiplied alpha textures or performing surface blending that preserves translucency. The function works only when blending is enabled via glEnable(GL_BLEND). When glBlendFuncSeparate is called, the blending equations for color and alpha are applied in the order defined by the current blend equation state via glBlendEquationSeparate.

In practice, programmers combine glBlendFuncSeparate with glBlendEquationSeparate and appropriate shader logic to produce sophisticated visual effects. The OpenGL specification documents the full set of permissible factor enums and provides detailed equations for fixed‑function blending. The command remains a fundamental tool for rendering pipelines that require precise control over how source and destination pixels combine.