Alpha planes are a great way to cut down on file size and import images for your renders, like trees, or even soldiers for making an image filled with an army, which would otherwise be impossible due to system requirements. They can be used to create ecosystems (object instancing), or as an alternative to ecosystems if you don't have that capability.

  Transparency can be used to great effect for other things, as explained in my tutorial on how to use transparency to blend in one material with another. This "trick" is extremely useful and I must stress how good it is to you! When making large, complex models, texture maps made for them can be excessively large, which you don't want as it hogs resources. Say you have a space ship, and want a decal to appear only on one area, but in detail. It is much easier and less resource hungry to make a very detailed but very small file sized .gif image in greyscale, to "cut out" a transparency, and then fill this transparency with a specific material or texture map. The result is you can make decals, text, dirt, weathering or specific materials appear where you wish.

  In Vue it's easy, set the material to 100% transparency, tick underlying material and variable transparency. Load any material you wish as the Underlying material (for decals a luminous or bright material is good), right click the Transparency function, go into the Material Editor, click "add texture map node", load your image, link it to transparency. This shows you how.

  To demonstrate how powerful an effect this is, please look at this image, it shows transparency cutting out the sails, and allowing the detailing on the main hull and legs. The files used to drive those effects were very small in memory space but the images were large to allow clear, precise "cut outs", the sail image is 1024x1024 and the gif file was only 39k in size, which is very small! The file used to drive the hull decals was 4096x4096, which is HUGE, but the file size was only 31k, tiny! The savings these allow in memory, and thus responsiveness of your 3d rendering program, is *enormous*!

Things to understand about using alpha planes and transparencies:

1) Alpha Planes use much less memory and resources than a full 3D object. Though a very large imported image in a file format that takes a lot of memory, like a .tif, can pose problems, i.e. importing a 4000x4000 .tif would take a lot of resources, but dozens of 512x512 .tifs wouldn't be much of a worry.

2) You need something to drive the transparency, often this is just a SELECTION saved to the Alpha Channel in the 2d paint application, like Paint Shop Pro or Photoshop.Alternatively, you can use another image in greyscale (black and white), .gif files are usually very good for this because of their small size. Grey scale gif files are very small in memory, you can reduce the number of colours in the .gif down to 16, if that is enough for good clarity, and thus make truly tiny file sizes.

-The image itself doesn't need to have a transparent background, though that often helps. With greyscale .gifs there's no need of a transparent background.
-Vue is odd, it often reverses the selection or works opposite to what you'd expect, just hit the small button near the image import to invert it.
-Only the first alpha channel is ever used to make transparencies in Vue, please note that. An image can have many alpha selections, but only the first will be used
-Grey scales generally work in that black = nothing (totally transparent or flat) and white = solid (opaque or very high).

3) Formats that support transparency or alpha channels are:

• .psd - Photoshop format, kind of large, can be slightly compressed, only the 1st layer and alpha channel will work in Vue, can be very high detailed and many colours (16 bit, but currently can't be imported as 16 bit in Vue6).
• .gif - format, this has a maximum of 256 colours, it's good for greyscales, and when using greyscales can produce very small file sizes, tweak the maximum number of colours down as desired to a minimum of 16. Mostly used to make images for the web, due to limited colour palette but small file size and transparency.
• .png - supports transparency, large file sizes is 16 bit colour, often used as web images an improvement on .gifs, has alpha channels.
• .tif Vue files saved as .tifs automatically have an alpha selections of models, objects etc, very hand tip! .tif files are not compressed and are very large, but high quality. Plus they can import as 16 bit greyscales, so they are awesome for terrains!
• .tga - this can support 16 bit greyscales in some cases (which is unusual but useful), but not compressed, so large file sizes.
  
  
  I hope this helps you :)

FINAL RENDER OF THE ALPHA PLANE