I am starting this thread because I am messing about with blender so if there is the off chance that other people can add to this pool that would be great but to start with ill add some things that I have discovered in the hope that they can be of some help.

After Bryguy told me about the built in scripts there was an impressive one amongst them which is the Poly Reducer - also known as a decimator. Well this is a very important tool for me and although I have several in various guises on my machine the built in one seemed to do a good job and didnt need me to export and re-import an object so that's very cool.

One of the things I was trying to do was clean up a section of a model which had too many polys in it so I selected that area and set the poly reducer on it and found that it reduced the whole model. Whaaaa my dummy went out of the pram again. I oscillate between hating this app and loving it. So back to google to see if I missed something and it turns out that blender cant poly reduce a selection.

Almost by chance tho I found a little tutorial which is a bit terse about this thing called the vertex weight painter and it meant that I had to get out of my pram and pick up my dummy cos its really good.

If you have a model with lots of verticees and faces in it like the monkey subdivided a few times (left image), you can go to a mode called the 'Weight Paint' above the object mode and edit mode at the top of that list.

The monkey comes up blue but where you paint with the mouse it goes red. So I have painted a cross of the head of him.

Now when you go to the poly reduce script there is a button to say 'VGroup Weightin'. What that means is that its going to add the weighting from the paint to the calculations for which faces to remove.

So once it has finished it comes out like the right image where the areas painted in blue get reduced a lot and those that were painted red get reduced not a lot.

Now that is back to front as far as I am concerned as a high weighting usually means a lot. But in a decimation the area of the poly is used as a means to say whether it should be zapped so small areas get zapped and large areas do not. So high weights mean keep them.

Otherwise for other kinds of operation which use it its done normally where a high weight means do it more.

Also note that you should assign the weight paint job to a vertex group instead of the default group but I didnt bother because my object had no groups in it.

Pretty cool huh ? I am back to loving this app again.