Ok, I tried the filter posted here which code is here. For this one is true that it just distorts the “red object’s” edges. For the TestSimpleRefractionFilter_Objects test package in the ShaderBlow project, however, it have the problem I said. I don’t know if it is because of the java code or because of the shaders themselves, could you point me where to look better for? (because I looked on the java code but I can’t see where they differs for having the different behaviour).
Thanks for the help 