type

Type controls bitmap 'geometry'. All dimensions must be a power of two except for SPRITES and INTERFACE BITMAPS.

* 2D TEXTURES: Ordinary, 2D textures will be generated.
* 3D TEXTURES: Volume textures will be generated from each sequence of 2D texture 'slices'.
* CUBE MAPS: Cube maps will be generated from each consecutive set of six 2D textures in each sequence, all faces of a cube map must be square and the same size.
* SPRITES: Sprite texture pages will be generated.
* INTERFACE BITMAPS: Similar to 2D TEXTURES, but without mipmaps and without the power of two restriction.

format

Format controls how pixels will be stored internally:

* COMPRESSED WITH COLOR-KEY TRANSPARENCY: DXT1 compression, uses 4 bits per pixel. 4x4 blocks of pixels are reduced to 2 colors and interpolated, alpha channel uses color-key transparency instead of alpha from the plate (all zero-alpha pixels also have zero-color).
* COMPRESSED WITH EXPLICIT ALPHA: DXT2/3 compression, uses 8 bits per pixel. Same as DXT1 without the color key transparency, alpha channel uses alpha from plate quantized down to 4 bits per pixel.
* COMPRESSED WITH INTERPOLATED ALPHA: DXT4/5 compression, uses 8 bits per pixel. Same as DXT2/3, except alpha is smoother. Better for smooth alpha gradients, worse for noisy alpha.
* 16-BIT COLOR: Uses 16 bits per pixel. Depending on the alpha channel, bitmaps are quantized to either r5g6b5 (no alpha), a1r5g5b5 (1-bit alpha), or a4r4g4b4 (>1-bit alpha).
* 32-BIT COLOR: Uses 32 bits per pixel. Very high quality, can have alpha at no added cost. This format takes up the most memory, however. Bitmap formats are x8r8g8b8 and a8r8g8b.
* MONOCHROME: Uses either 8 or 16 bits per pixel. Bitmap formats are a8 (alpha), y8 (intensity), ay8 (combined alpha-intensity) and a8y8 (separate alpha-intensity).

Note: Height maps (a.k.a. bump maps) should use 32-bit color; this is internally converted to a palettized format which takes less memory.

usage

Usage controls how mipmaps are generated:

* ALPHA BLEND: Pixels with zero alpha are ignored in mipmaps, to prevent bleeding the transparent color.
* DEFAULT: Downsampling works normally, as in Photoshop.
* HEIGHT MAP: The bitmap (normally grayscale) is a height map which gets converted to a bump map. Uses <bump height> below. Alpha is passed through unmodified.
* DETAIL MAP: Mipmap color fades to gray, controlled by <detail fade factor> below. Alpha fades to white.
* LIGHT MAP: Generates no mipmaps. Do not use!
* VECTOR MAP: Used mostly for special effects; pixels are treated as XYZ vectors and normalized after downsampling. Alpha is passed through unmodified.

post-processing

These properties control how mipmaps are post-processed.