Author: HobbitDur

Dynamic texture data

Optional section, often empty. It contains info on dynamic texture (like blink-eyes)

It starts with a list of offset followed by data. The offset list start with a 0 offset which must be ignored. Each offset is 2 bytes. The number of offset need to be deduced: so read each 2 bytes till you read a bit that is inferior to the previous. The offset value start at the beginning of the section.

Each data pointed by the offset look like this:

struct DynamicTextureData
{
  BYTE textureNum;                      ///< Which texture page/slot to use
  BYTE vram_x_offset;
  BYTE vram_y_offset;
  BYTE sprite_width_in_vram_coord;      ///< Width of region to copy, in X you need to multiply by 2 to get the pixel value
  BYTE sprite_height_in_vram_coord;     ///< Height of region to copy
  BYTE number_destination;
  BYTE anim_speed;                      ///< Playback speed (see below); 0 = scroll mode
  BYTE frame_counter;                   ///< Runtime accumulator, always 0 in the file
  BYTE source_uv_u;                     ///< X offset of source sprite in VRAM (x2 to get pixel for X)
  BYTE source_uv_v;                     ///< Y offset of source sprite in VRAM
  UV_VRAM dest_uv[6]; ///< Actually pairs of bytes: {dest_u, dest_v} for each frame
};
struct UV_VRAM
{
  BYTE u;                               ///< X in VRAM (x2 to get pixel)
  BYTE v;                               ///< Y in VRAM
};

The number of dest_uv depends of the number_of_destination.

Important point is that all UV and sprite width/height is expressed in VRAM value, which mean you need to multiply the X value by 2 to get the pixel value (Y is already in pixel).

Playback (anim_speed / frame_counter)

The animation is advanced by animation sequences opcode 80. Only anim_speed comes from the file; frame_counter is runtime state (0 on disk):

  • anim_speed == 0 — scroll mode: the copied VRAM region is scrolled rather than frame-swapped. (number_destination is 0 in this case.)
  • anim_speed == 8 — one destination frame is shown per tick; frame_counter cycles 0 .. number_destination.
  • any other value — anim_speed is a speed in 1/8-frame units: each tick adds it to frame_counter (which runs 0 .. 8*(number_destination+1)), and the visible frame is frame_counter / 8. So smaller values play slower, 8 is one frame per tick.

TODO: Add the monster list that have an animated texture section.