I am working on a project for school with Gamestudio and we want models to have transparent parts. But if any part of the model is transparent, the rest of it is also transparent.

Do you guys know how to fix this?

Thanks for any help.

Use 32 bit TGA textures. Use the alpha channel of the image to control transparency. You will not need to set any flags or alpha values in 3DGS. It just needs the texture with an alpha channel.

The GIMP is a good [free] paint program that allows you to edit the alpha channel.

Mark those parts of bmap (.tga) you want to have invisible with f.e. magic wand. Then fill those parts with black color. Save this mask as alpha channel. Next delete this mask without merge it with screen. Save as... .tga. End of story

If you'll have problems with sorting, check out WIKI, alpha-test shader will fix 'em

More problem is (for me) how to make model where different parts have differents materials?
F.e. metallic & shiny car's body with reflections and mat rubber wheels?

In your case it's no problem
You apply the shiny material to the whole car and make the 'shinyness' depend on the diffuse skin's alpha channel. Scorpion posted a "cubemap shader with glossmap" in user contributions, that's what i mean
I think in most cases it can be done this way

You'd normally want seperate models for tires and car

but separate is not the best option I think...
one entity for body, another fo wheels, next one for rims... that sounds no good

you only need five, one for the car and the four wheels, i think thats what xxxguiter meant, not tires. and there is a tut in the aums about just this thing.

no I need 1 for car, 1 for 4 weels, 1 for 4 rims, 1 for lights... minimum 4 entitys to make f.e. one car
And think about 12 cars * 4-5 entitys and looooot of loops with vec_for_vertex to keep right position
I think it could be done by shaders or multiskin somehow but how? no idea
I don't need this right now but it's interesting, isn't it?