glBlendFuncGLenum

glBlendFunc is a function in OpenGL that sets the factors used in blending. Blending is the process of combining the incoming fragment's color with the color already in the frame buffer. This function takes two arguments, sfactor and dfactor, which are enumerant values specifying how the source color and destination color, respectively, are scaled.

The source factor determines how the color of the incoming fragment is multiplied. For example, GL_ONE multiplies the source color by 1, meaning it's fully used. GL_SRC_ALPHA multiplies the source color by its alpha value, making it more transparent if the alpha is less than 1.

The destination factor determines how the color already present in the frame buffer is multiplied. GL_ONE_MINUS_SRC_ALPHA multiplies the destination color by 1 minus the source alpha value. This is commonly used for alpha blending, where a semi-transparent source color is blended over a destination color. The resulting color is a weighted sum of the source and destination colors.

Commonly used enumerant values for sfactor and dfactor include GL_ZERO, GL_ONE, GL_SRC_COLOR, GL_ONE_MINUS_SRC_COLOR, GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_DST_COLOR, GL_ONE_MINUS_DST_COLOR, GL_DST_ALPHA, and GL_ONE_MINUS_DST_ALPHA. The specific choice of factors allows for a wide range of blending effects, from simple transparency to more complex compositing operations. For instance, using GL_ONE for both sfactor and dfactor results in additive blending, where colors are simply added together.