In the Apple GLPaint app, the user can paint with a translucent brush over the surface and change colors.
However, as of iOS7, for some odd reason it’s impossible to draw something that completely follows its background: in the first image we see “Shake me”, written in green, and a red drop that was painted several times above him. However, the following figure is still barely noticeable. The second image was desaturated to make the defect more obvious.
The OpenGL mixing function that Apple uses is:
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
What I expect is to mix new translucent brush strokes over their background until it is no longer seen.
?