2D perspective correct texturing ?

[Ñuño Martínez]

Why do I have feeling that Nuno spends too much time on communities like Stack Overflow?

I don't know, because I never used Stack Overflow, and I don't know if any other or the communities I spend too much time on are like that as I never used it.

I would expect such answer on the Stack Overflow where most people blindly tends to answer the question that was asked and not the question that was intended to be asked.

I can answer this:

That's because, in my experience, the question that was intended to be asked is often not the actual question that should be asked. And if I've understood correctly the other messages, this is one of these cases. (Please, correct me if I'm wrong in this: I'm still learning English)

So Nuno can you please provide short example for rendering skew quad using OpenGL?

Of course I can, but it would be too similar to the one provided by phibermon.

[Disclaimer]: I must apoligize. Some times I can be too much sarcastic. Please, no offense intended. If you think I've exceed the limit, please tell me and I'll try to keep my responses under control. Really.

Didn't you also messed up with the coordinates here? Specifically for second triangle?

...

Shouldn't the order of coordinates for second triagnle be TopLeft, BottomRight, TopRight?

Yes, on the first triangle is counter-clockwise and the second is clockwise. Both them should have the same "wise" to use back face culling correctly.