displacement mapping issues

<span style="font-family: verdana;">Ok,
I have my whole map layed out (in block brushes only, this is just the
terrain) and I wanna create the terrain using displacement maps, but
when I subdivide the map (the whole thing) parts of it go askew and
other parts become missing. Just curious if anyone else has had this
problem and knows how to fix it, I already read and re-read Reno's and
Fakedawg's tuts on displacement maps so...<br style="font-family: verdana;">
<br style="font-family: verdana;">
Anyway, if anyone knows whats wrong plz help.

</span>

<span style="color: cyan;">This colour gets really annoying after the first word, try not to use it again. There's nothign wrong with white.

Anyways, I think you may need to go into more detail. If you are
making flatland, those parts shouldn't be subdivided, only things like
cliff faces should if you're going for a realistic look.

Also remember, it states that in the tutorial, only the highlighted
faces will turn into displacements, and the others get deleted, this
may be the dissapearing part of your question.

If you can be a bit more detailed in your description, maybe providing a small screenshot, then it will be easier to help you.

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