GMax, Alpha Textures, Transparency, Frame Buffer Blend, FSX Material Options, .psd To .DDS Conundrum

Hello fellow builders and painters. If that title didn't give you an idea of the topic I am wondering about, let me explain. BTW, I titled it this way so that others might find this thread for answers to their own similar problem by searching any of those words. Hopefully a discussion here might be of use to a learning modeler. There is so much confusing information on the internet, nothing is specific to this question that I've found (and I've searched believe me).

I'm having a hard time understanding how to get alpha textures to work in FSX, with a Gmax designed object. So far in my project, following online advice, tutorials, SDK reads, and videos, when I export my scene (no problem there, everything else looks great) and open the object in FSX, the effect is either not present, or not correct. Texturing to me, the manipulation of images, is such a puzzling convoluted science with all it's technical descriptions and techniques, I usually have to backtrack to try and understand things before I can move ahead successfully. Which just delays everything I'm trying to do for another day, and another day. (Much like life I guess.) If you can relate, I would like to ask the experts here if they might shed some light for us learners. And I don't mean _lm light! :)

I designed a hangar in Gmax based on a real world airport. There is painted numbers and signage all around the hangar. What I am trying to do is, create a material where the white background of the material sheet is transparent, and only the letters appear, to look as if they had been painted on the hangar walls. I do not want the white background of the material sheet to display. Just the lettering and images. I've created a square polygon, textured it with the airport sign. Stumped from there.

I have read in the SDK about how the settings in a newly created FSX Material work using the framebuffer blend section in GMax, but have not figured out if the alpha is created separate, or is placed in the layered .psd file (prior to converting to .DDS), where the diffuse alpha layer goes in the layering order, what format it should be, how it should be named, or if in fact other options in the (FSX format) Material Editor should be check marked as well. I feel I/we could really use a simple explanation with visuals if possible. When explaining, I will try my best to follow along and report my success. Thank you sincerely.

Hi Doug,

Alpha isn't a layer, it's a channel, just like R, G and B are channels. Each pixel has an RGB value, and can also have an A (Alpha) value, so we refer to an image with Alpha as RGBA.

To add Alpha, go to your Channels panel and if you only have RGB, add a channel (much like adding a layer).

You can paint into individual channels. Paint some areas of the Alpha channel black and some white. Then in the Material Editor hit the Set Default Transparent button. This button is just a shortcut that sets your blend to Source=SrcAlpha, Dest=InvSrcAlpha. This means that your material (the source) will be blended into the image (the dest) according to the value of Alpha. If Alpha is very low, for example black which is zero, then your material is not visible at all and whatever is behind it in the scene is visible. If Alpha has a very high value (eg white which is the max value typically 255 for an 8-bit channel), then your material completely covers anything behind it in the scene. If you use some intermediate (gray) values, then your material blends with what is behind it in the scene (lighter = more opaque).

Alpha doesn't have to mean transparency, it's up to the settings in your model. It can control blending of environment map instead to make the material look reflective.

A good exercise is to work through the FSX Materials section of the SDK docs. Don't just read it, make a teapot and all the textures described and play around yourself. Also make sure to get ModelConverterX, it can render many of the FSX material settings and you can change them on the fly, though some effects probably need to be put into the simulator to see properly.

One other thing, if you are putting one textured polygon over another you might get flickering, just something to be aware of. If you put enough gap between the polygons you should be OK.


Resource contributor
And if you use a program like DXTBmp you can create two completely separate images - one for the RGB diffuse bitmap and another for the alpha channel bitmap. Then you can use DXTBmp to combine them together in the final step of creating the DXT format bitmap.