Extra arg for varender* to denote blend mode as per glBlendFunc
Leaving this as a mental note:
PARAMETERS
sfactor Specifies how the red, green, blue, and alpha source blending
factors are computed. Nine symbolic constants are accepted:
GL_ZERO, GL_ONE, GL_DST_COLOR, GL_ONE_MINUS_DST_COLOR,
GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_DST_ALPHA,
GL_ONE_MINUS_DST_ALPHA, and GL_SRC_ALPHA_SATURATE. The initial
value is GL_ONE.
dfactor Specifies how the red, green, blue, and alpha destination
blending factors are computed. Eight symbolic constants are
accepted: GL_ZERO, GL_ONE, GL_SRC_COLOR,
GL_ONE_MINUS_SRC_COLOR, GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA,
GL_DST_ALPHA, and GL_ONE_MINUS_DST_ALPHA. The initial value is
GL_ZERO.
Todo:
Leaving this as a mental note: