Video Track Motion like After Effects

Hey guys,

Hope everyone well,

I am performing some challenges to myself, trying to code some things of AfterEffects on openframeworks, like this one http://www.videocopilot.net/tutorials/basic_sky_replacement/

• video : OK
• image : OK
• linear wipe (shader/alpha mask) : OK
• color key (shader) : OK
• key tracking (openCV how?) : missing
• post production (fbo + shader) : missing

Somebody can give me a hand to build this Track Point thing? similar like screenshot attached

PS: I am brazillian, so my english be a crap haha

Thanks in advice.