Animating particles using SubUV charts
Suppose you are creating an explosion effect for a film. You might go out and shoot video of flames against a black background so you can mix that footage into the effect. For a one second blast you'd wind up with 30 or so frames, which is no problem in a film, but in a game, you have to handle all those frames. One method is to spread the frames from the explosion onto a single grid and then read off each square in the grid in series. In Cascade, the term SubUV refers to rendering part of a texture onto a sprite. You can combine textures onto a grid, such as 4x4 or 8x8, and tell UDK to use SubUV for the texture and it will parse each of the grid squares for content to render. This can be done by stepping through the grid squares in order (linearly) or randomly.
Getting ready
Furnishing a 1024x1024 SUBUV texture card grid:
I'm going to assume the use of Photoshop for image processing in the book but you could use any equivalent image editor like GIMP...
