You may have long wanted to make your own cloud maps for povray, vrml, Celestia or whatnot and could not understand the
more sohpisticated methods for creating the transparency needed. Many of you tried to make a transparency using the
gif transparent background and then found out that the edges of the clouds were opaque and ugly and unrealistic. Then you probably
a stumbled on to the info that you needed to use a different format plus adding an extra alpha channel for the transparency data.
You then found that you needed some large graphics program such as photoshop. In this tutorial we use Photoshop 7 and you must
obtain also the free plugin called lunacell which makes the planet maps and cloud maps; which are then exported to the Photoshop
work area for transparency treatment and saving in dds format. You can download the plugin and dds tools at these url's:
Lunacell by Flaming Pear and
Nvidia DDS tools!
I have only one more thing to say here about the plugin dds.8bi and that is that there are 3 of them and one is the basic and
two are the advanced and one of the advanced I could not get to work; but anyhow the one that works is 472 kb.
You do not want to go through all the trial and error I did; just accept my advice and do your astronomy using the free Celestia program which is at sourceforge.net and also at shatters.netShatters.netandSourceforge.. But here is one more thing: you want celestia version 1.3.1 version 1.3.1 downloadbecause you want the large planet maps like everyone else and newest addons. Celestia is only 11mb for the main program but with all the addons and high resolution planet maps it adds up to probably well over 1gb. I spent 3 or 4 days installing all the extras and hires maps. It is not simple at first but once you understand it then it is clear sailing hopefully. I tried making my own alpha channels and only ended up in despair and then I downloaded the Nvidia tools and things became much easier.
First you open the new files menu and make a starting window of binary dimensions which means it
must be 256 or 512 or 1024 or 2048 etc on each side. I chose 1024x512 for the example!Set it like here in
the example window and be sure is RGB format or it will not save in DDS format.
After you do this then start the lunacell plugin and make a cloud map and export to your window. This is basically self explanatory. Click on the icon in the middle of the screen under the axis control and choose the cloud map and then adjust it with the sliders and export it. I would not bother with the real cloupmap download at this point because the images are not much good.
After you do this then you must make the alpha channel by choosing the image calculation option!
You will then have the following screen which is an important one also! This one makes your alpha channel! Just click on okay.
You will now see a new channel in the bottom right hand window with your main channel and your three RGB channels!
Now I want you to double click on the new channel and inspect to see if it looks like the example below!
You can now prepare to save the file in dds format; being certain to check the alpha channel and save it too.
You now see the final window and probably you may want to check so that it makes MIP maps. MIP maps are like having Levels of Detail in VRML and other 3d environments such that when you get closer to the object or planet you get a more detailed view. This keep the processor from over working. With DDS format you also see that images are tiled sometimes which is nice but it is messy and time and energy inefficient. This would mean making dozens and dozens of tiles if you wanted to have not only the main map but also nighttexture and normals or bump map and specular etc. This is not that necessary. The point probably is one of processor speed and ram size. If you have 512 mb ram and a really fast cpu and a video card with 256 mb ram then you probably dont need tiles. The MIP is like having several different resolution images all together inside one large dds file. If you reload the file you made after saving then it will show you the MIP maps you made and the images will be elongated from left to right. Also if you use tiles you have to make an additional file with format ctx and point the program towards it. Using a single dds file is much simpler.
It is a bit tricky at first making the cloud map with lunacell because it does not look exactly like you thought it would but it does create the variable transparency you wanted to give you good realism. Enjoy!
Questions! email and I will try to help!