Blending is an important effect. All antialias effects (see below) depend on blending enabled. Blending means that the alpha value of each pixel will be calculated when drawing the scene. When you take the border of a stone or a grid line, the pixels close to the wooden board will have a lower alpha value, so the borderline will not appear blocky, instead the edge of the black grid lines or the stones will be smooth. When blending is disabled, all antialias effects will not work. Blending is a recommended feature, however it can be quite performance costly in software mode. You need to find out if trading the performance for quality is worth it. When running in hardware mode, blending is very fast and should be enabled.