Render Sequence of Materials
The sequence of the materials specifies which materials are last rendered. So it is important that glass/transparent materials are rendered after the other materials, otherwise there is nothing behind them. For example, luminous materials are rendered in the same way according to the normal materials, so that they can cast some light on them. However, the system also has its pitfalls, as light cannot be displayed behind glass like this. If objects are not visible behind windows, it helps to rotate the materials used or to define an order within the same material via order = 1.
Structure of the material files
This list should give you an overview of which materials need which parameters in the mtl's:
Ihr könnt euch hier auch gerne die Tabelle als PDF herunterladen:
Channel assignment in the textures
The "Albedo": 3 or 4 Channels
RGB: standard texture
A: Transparency: black = 100% transparent, white = opaque, shades of grey around 128 (50%) recommended.
Normalmap: 3 Channels
cblend_dirt_rust: 3 Channels
R: Color (Colorblend): black areas are recolored, white for unchanged areas, gray tones for transitions
G: Dirt: more white means more dirt
B: Rust: more white means more dust
metal_gloss_ao: 3 Channels
R: metallic gloss/matt gloss: whiter gloss
G: Reflections: White stronger reflections
B: Ambient Occlution: Calculated on white, grey areas = shades
Allowed texture formats
Basically all textures may be in DDS or TGA format. While TGA are uncompressed and take up a lot of space, DDS files are lossy. More about the DDS formats can be found here.
HDR textures can also be used for EMISSIVE materials.