Textures and materials, built on the fly

After the interface art, the next job was the big one: every texture in the install, and the materials that decide how each one is drawn.

Textures

The original’s DTX textures are converted into a textures pack. A texture’s header carries more than pixels (what kind of surface it is, how it’s scaled in the editor, detail-texture settings), so that’s kept too, as notes on the pack entry.

One subtle thing: the original’s alpha isn’t always transparency. Plenty of skins carry an alpha channel that’s just noise, and a texture marked as full-bright uses alpha to mark its glowing pixels. A texture is only treated as transparent when its header actually asks for it, and a short list covers the few that can’t be worked out from the file alone.

Materials as data

A material isn’t an asset here. It’s a small record saying which texture to use and how to draw it, and the game builds the real material from that when it needs it.

Every material has a key: the texture’s path, followed by any options in a fixed order.

TEXTURES/LEVELTEXTURES/WATER/WATER1.DTX                  the texture as-is
TEXTURES/LEVELTEXTURES/WATER/WATER1.DTX#alpha0.7         at 70% opacity
SKINS/PROPS/LANTERN1.DTX#transparent#chrome              alpha used, environment mapped

The same texture used two ways is two materials, and a map always finds the one the converter made for it, because both build keys in the same place. A small set of template materials ship with the game, one for each combination of lighting and blending, so the shader variants they need are never stripped from a finished build.

The converter works out which materials to make by scanning how the maps use things: surfaces and their flags, water and lava volumes, props and their skins, and the world’s sky and environment settings.

Effects and models

• Effect textures that the original made by turning or laying out another texture, such as a trail rotated to run along a bolt, or a sprite’s frames in a grid for a particle system, are produced from the originals by a fixed recipe, and match the ones the effects were originally built with pixel for pixel.
• Models and their skins. A table of which model wears which skin is written during conversion. Some pairings aren’t in any data file, because the game’s code chose them, so those are listed separately and any missing file is reported.
• Readers for the rest. Readers for the original’s model (ABC) and world (DAT) formats came across from the converter project. They only read for now; building from them comes next.

What’s next

Sounds, then the first map.