Blending filter
lab16-BlendFilterTextureShadedQuad
glEnable(GL_BLEND);
if (g_filter == 0) // Default (no blending) = Cs*1
glBlendFunc(GL_ONE, GL_ZERO);
else if (g_filter == 1) // Draw background only = Cd*1
glBlendFunc(GL_ZERO, GL_ONE);
else if (g_filter == 2) // Cs*1 + Cd*1
glBlendFunc(GL_ONE, GL_ONE);
else if (g_filter == 3) // Alpha blending (back-to-front) = Cs*As + Cd*(1-As)
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
else if (g_filter == 4) // brighten the scene = Cs*As + Cd*1
glBlendFunc(GL_SRC_ALPHA, GL_ONE);
else if (g_filter == 5) // Modulate blending = Cd*Cs
glBlendFunc(GL_ZERO, GL_SRC_COLOR);
else if (g_filter == 6) // darken the scene = Cd*As
glBlendFunc(GL_ZERO, GL_SRC_ALPHA);
else if (g_filter == 7) // Invert all the colors = Cs*(1-Cd)
glBlendFunc(GL_ONE_MINUS_DST_COLOR, GL_ZERO);
Default (no blending)
Draw background only
Add blending
Alpha blending
Brighten the scene
Modulate blending
Darken the scene
Invert all the colors
