gMax Transparancy
 

gMax supports several file formats that allow you to have transparancy in your objects based on the alpha channel contained in the image. In this tutorial I will show you how to get this to work inside gMax itself. The the file formats that gMax reads the alpha channel for are as follows.

TGA: Supports varied levels of transparancy based on a 256 level gray scale alpha. Very universal as most all graphics editing programs support this format. This is closest to the 888-8 format of Imagetool and DXTBmp and is not compressed so the files can be quite large and use a lot of memory when loaded.

PNG: Supports simple black and white alpha channel meaning the black is fully transparant and the white is fully opaque. This format is much like JPG as the data is compressed but with much less loss of quality. I think you could say that is closest ImageTool or DXTBmp format would be DXT-1 but with 24 bit color opposed to 16 bit and no mips.

ACE: A file format developed by KUJU for the Microsoft Train Simulator. Requires that you have the KUJU.ACEImage.bmi plug-in from the MSTS gamepack installed in your gMax plugin directory. Supports varied levels of transparancy based on a 256 level gray scale alpha. Very similar to the 888-8 format and supports mips. There is also an 888-1 ACE format similar to DXT-1, but I have not seen a file in that format that the Makeace.exe program did not mess the alpha channel up so I'd just forget about using that format. More about using this format in a minute.

PSD: Adobe Photoshop. Varied levels of transparancy but not all versions are supported

Now, on to making it work.

 
You apply and map your texture just as you would any standard opaque texture. The trick is what you do afterwards.
 
 
After you have applied and mapped your texture to your object, in the Material Editor, Maps section, grab the box for the Diffuse Color and Drag and Drop it on the Opacity box.
 
 
You will get a dialog box for the Method where you will choose Instance. This means that the texture will only be loaded once and if you change the Diffuse Map, the Opacity will also change and vise-versa.
 
 
Next in the Bitmap Parameters section, besure the buttons that I have marked in red are selected.
 
 

Now you should be able to see your transparancy in gMax.

If you are building for the Microsoft Flight Simulators, when you go to export, you may get an exporter error message about having a texture assigned to an unsupported map channel six. This will pop up for every part that has this method used on it. Not to worry, just click OK and move on. It will just ignore this and export just fine.

If you are building for the Microsoft Train Simulator you do not have to do all of your work in the gamepack itself. I do most all of my work outside of the gamepack so I can use the less confinning gMax Material Editor and see my transparancy. This is why after installing the gamepack I have moved the KUJU.ACEImage.bmi from the gamepacks plugin directory to the main gMax plugin directory making it universally avalible wheather you are in a gamepack or not. This also allows me to use the image translator for the MSFS gamepacks and use ACE files there. The only time I use the actual MSTS gamepack is when I am ready to export. Then I open my externally built scene, make a change a few settings using the gamepacks material editor and LOD tool to setup for exporting. The transparancy will still show in the gamepack but the inferior material editor doesl not let you change the transparany map. If you change the material/texture inside the gamepack, you will probably loose your internal gMax transparancy. I will save the scene to a new gMax scene with an *_TS.gmax extension so I know it has be modified by the gamepack and my original externally built scene is still intact.

This may all seem a bit confusing to start with but once you have done is a couple of times you will see is it a piece of cake.

 
07-03-2006