Blending 예제
http://dis.dankook.ac.kr/lectures/cg08/entry/blending-예제

Blending Filter 예제
http://dis.dankook.ac.kr/lectures/cg08/entry/blending-filter-예제

// Default (no blending) = Cs*1
glBlendFunc(GL_ONE, GL_ZERO)      
// Draw background only = Cd*1
glBlendFunc(GL_ZERO, GL_ONE)  // Addition Blending = Cs*1 + Cd*1
glBlendFunc(GL_ONE, GL_ONE)    
// Alpha blending (back-to-front) = Cs*As + Cd*(1-As)
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)  // Brighten the scene = Cs*As + Cd*1
glBlendFunc(GL_SRC_ALPHA, GL_ONE)  // Multiplicative blending = Cd*Cs
glBlendFunc(GL_ZERO, GL_SRC_COLOR)// darken the scene = Cd*As
glBlendFunc(GL_ZERO, GL_SRC_ALPHA);// Invert all the colors = Cs*(1-Cd)
glBlendFunc(GL_ONE_MINUS_DST_COLOR, GL_ZERO)