I don't quite know how to explain this, but I have a misc_portal set up and working correctly in SP. I noticed that when you get a certain distance away from the misc_portal surface you can't see 'through' the portal.

Is there a way to change this distance and what is the default? I'm using the common/glass_portal texture if that makes a difference.

As I said I am rubbish at explaining things!

I know what you're saying, and unfortunately, I don't think there's any way to fix it.  I'm pretty sure the distance is hardcoded to maintain FPS.

Nope, its not hard-coded. Its controlled by 'alphaGen portal' in the shader. To get rid of it completely, simply use the textures/common/mirror1 texture for your portal surface. Even though it's called 'mirror1', it can still be used for both mirrors and portals.

I tried the textures/common/mirror1 texture and all I got was the HoM effect. It's definitly that texture because when I replaced it with a different portal texture it worked just fine.

Nevermind then...

ummm.... I don't think it worked, although that may be an error on my part, i'm not sure, its my first time manipulating game files. I opened up the common shader scripts in shaderEd, changed the Alpha Gen Portal portal range to 2048 and saved. It had no effect so I tryed 9999 and it didn't work either. Then I opened common in notepad and changed it there but again nothing happened. I tried this with three portal textures with the same results.

You really shouldn't change any of the game's shaders.  Copy them into a new file and make your own .shader then change that.

Even if it is possible to increase the viewing range, you still have the crappy swaying effect which is apparently hard-coded into the EXE.

Correct me if i'm wrong but I think that swaying effect only happens in multiplayer, not in singleplayer.