isometry

This script-fu rotates an image -/+ 26.57 degrees to help to make an isometric roof. There are some little options to resize, to cut the semi-transparent pixels, to merge down.
I don't know if this script will be very useful. It is for me, so I am sharing.

You can find "03 - Isometric Roof (26.57 degrees)" in Filters>2D Isometric-Fu>

example:

This script-fu skews an image in order to help to draw walls for isometric projection. It can also scale image with few options (ratio, a second layer with interpolation and opacity)...

For further explanation, see also http://registry.gimp.org/node/25040

You can find "02 - Isometric Wall" in Filters>2D Isometric-Fu>

example:

This script-fu turns a "flat" image into isometric image. This helps to draw floors. It can also scale image with few options (ratio, a second layer with interpolation and opacity)...

You can find "02 - Isometric Floor" in Filters>2D Isometric-Fu>

example:

Why is there "a second layer with interpolation and opacity" for scaling?
There is always a first layer without interpolation to try to keep the grain texture. This is practical for stone for example. The opacity of this layer is always 100%.

This script-fu creates an isometric tile in your patterns and a template from it.

You can find ""00 - Isometric Tile and Template"" in File>Create>Patterns or in Filters>2D Isometric-Fu>

example: