A bitmap (or "map of bits", also known as raster graphics image) is a dot matrix data structure, representing a generally rectangular grid of pixels.
Raster images are stored in image files with varying formats. In the PC version of Re-Volt, the file extension used for textures is the BMP, which most image editors can create and modify, including Microsoft Paint. Dreamcast version uses PVR files, and Playstation uses BIN (which are basic RAW images) and PAL (palette files).
The legacy engine standard dimension for textures is 256x256 pixels, 24-bits. Textures are auto resized if they aren't within the standard, but odd artifacts may occur if the size difference is too much big. Fortunately, the Re-Volt fan patches 1.2 and RVGL allow the use of higher dimensions without resizing it to 256x256 pixels.
Re-Volt has a limit of how much bitmap files can be used in each track, being 10 files the standard limit. These files are named with the level directory name, and a letter in the end varying from A to J (market1a.bmp, market1b.bmp, etc.). They can be also called as Texture Pages or Texture Sheets.
RGB colors set as 0 0 0 (pure black) are not displayed in the game, becoming invisible/transparent. This method was commonly used in video games for creating detailed objects without surpassing the poly count, mostly for vegetation. A clear example can be seen in the Botanical Garden level, or the supermarket Shopping Cart.
Pure black transparency also applies for mipmaps.
The patch RVGL came up breaking several barriers in Re-Volt, including texture limitations. Some of the new features are as follows:
RVGL currently supports greater texture sizes that work with any graphics card. It had currently set a higher limit of 8192×8192 pixels. The most used sizes are 1024x1024 and 2048x2048 textures, since larger sizes might have a negative impact on the game's performance.
To keep the compatibility with the legacy versions of the game, textures higher or lower than 256x256 pixels usually have their extension renamed and are included in tracks and cars as mipmaps. The nomenclature consists of changing the last letter in the extension (in the case of BMP, the P) to a higher or lower letter in the alphabet, taking the sizes in consideration.
This also serves as "texture sets". In other words, the game will choose the texture size that fits better with the available system resources.
Not to be confused with the mipmap formats.
RVGL have support for other texture formats. They're: PNG, JPG, WEBP, TIF, GIF, CUR, ICO, LBM, PCX, PNM, XPM, XV, XCF and SVG. Textures still need to have their extensions renamed to BMP. Mipmaps uses their standard nomenclature as well.
Alpha Channel Transparency
RVGL also supports bitmap textures with alpha channel for transparency data (32-bit ARGB). This can be used for several effects as gradients and anti-aliasing.
Have multiple skins for a single car is permitted in RVGL. Available skins can be selected by the player in the car selection screen, and are also randomized for CPU cars.
Skins are detected based on a suffix system, similar to the tracks multiple bitmaps but not restricted to letters. In order to be detected, skin names must start with the main texture name (from the TPAGE line) and a suffix in the end from the author's preference.
Track textures limit
As of version 19.0120a, RVGL supports up to 64 level textures with an extended naming scheme. Suffixes of texture names along with their ID are listed in the table below.
Tracks with more than 10 textures will not work correctly in older versions, including Re-Volt 1.2 and the legacy versions of Re-Volt. Furthermore, until the moment, extra texture pages can only be added with Marv's Re-Volt Add-On for Blender.