How to join 2 images??

There are a bunch of ways. I think in your case you might wanna try experimenting with the threshold component.

Put image 1 into the high or low of the threshold input, and image 2 in either high or low. Experiment with the "threshold" and "smooth" settings to get the best of your options.

Also, just a quick tip based on your screen cap: your profile gradient is capable of producing what you're doing in the blur component. Basically, you don't need the blur component because the profile gradient can generate that pattern. This saves you render time! If you need help, ask away!

Do you mean that you have to have one full square with the image, and then exactly same full square image reflected with the water distorsion just below the one above?

This would make an rectangle (2 square one above the other) and so you would need to modify the output resolution to be rectangular in the same way.

The problem is that as far as I know all the components of filter forge will give a SQUARE result and not a rectangular one, so you could fit a rectangle inside the square, I mean that you can mix the images with the blend component, or with threshold, or with Add component, or other possible but always the result will be square, unless I am missing something and I may be wrong.

Sorry that I can´t help more

Thresholds are indeed a good way to do this; moreover it is a good practice to use thresholds performancewise (only one sample path is used per zone, http://www.filterforge.com/wiki/index..._Clipping)

Take a look at the wiki site for many good tips, tricks and techniques:

http://www.filterforge.com/wiki/index...nstruction