Changing alpha of white lines in fbo turn them to black

Hi, openFrameworkers,

I try to fade out a white lines (ofBezier) in fbo, but before they disappear the color turns to black. I typed ofEnableBlendMode(OF_BLENDMODE_ALPHA); just everywhere and set fbo to GL_RGBA16 but it does not help…

What a problem could be there?
Thanks!

Could you post a snapshot of the result you’re getting?

This is kind of a manta in water…

screenshot of a full transparency:
http://www.tiikoni.com/tis/view/?id=ff42083

screenshot of a decreasing transparency:
http://www.tiikoni.com/tis/view/?id=87b1d63

Check this topic, the problem is that alpha values are probably accumulating or multiplying when they go from the ofFbo to your screen. For more info read on glBlendFunc and glBlendFuncSeparate.