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The Individual Resources: A summary

The resource types of SCI0 can be roughly grouped into four sets:

Text resources are nothing more than a series of ASCIIZ strings; but the other resources deserve further discussion.

Graphical Resources Summarized

The screen graphics are compromised of the four graphics resources. The background pictures are drawn using vector-oriented commands from at least one pic resource (several resources may be overlaid). The fact that vector graphics were used for SCI0 allows for several interesting picture quality improvements. Pic resources also include two additional "maps": The priority map, which marks parts of the pictures with a certain priority, so that other things with less priority can be fully or partially covered by them even if they are drawn at a later time, and the control map, which delimits the walking area and some special places used by the game logic. FreeSCI uses a fourth auxiliary map for during drawing time (this is a heritage from Carl Muckenhoupt's original code).

View resources contain most of the games' pixmaps (multi-color bitmaps). Each view contains a list of loops, and each loop contains a list of cels. The cels themselves contain the actual image information: RLE encoded pixmaps with transparency information, and relative offsets.

View resources are used for foreground images as well as for background images (for example, the "Spielburg" sign in QfG1 (EGA) is stored in a view resource and added to the background picture after it is drawn).

The cursor resource contains simple bitmaps for drawing the mouse pointer. It only allows for black, white, and transparent pixels in SCI0.

The fourth graphics resource is font data. It contains bitmapped fonts which are used to draw most of the text in the games. Text is used in one of four places: Text boxes, Text input fields, the title bar menu, and occasionally on-screen.

Sound Resources Summarized

SCI0 uses two types of resources for sound: Patch resources, and sound resources. Sound resources contain a rather simple header, and music data stored in a slightly modified version of the MIDI standard.

Patch resources contain device-dependant instrument mapping information for the instruments used in the sound resources. SCI0 sound resources do not adhere to the General Midi (GM) standard (which was, to my knowledge, written several years after the first SCI0 game was released), though later SCI versions may do so.

Logic Resources Summarized

Whenever the parser needs to look up a word, it looks for it in one of the vocab resources. This is not the sole purpose of the vocab resources, though; they provide information required by the debugger, including the help text for the debugger help menu and the names of the various SCI opcodes and kernel functions.

Script resources are the heart (or, rather, the brains) of the game. Consqeuently, they also are its most complex aspects, containing class and object information, local data, pointer relocation tables, and, of course, SCI bytecode.

To run the game, scripts are loaded on the SCI stack, their pointers are relocated appropriately, and their functions are executed by a virtual machine. They use a set of 0x7d opcodes, which may take either 8 or 16 bit parameters (so, effectively, there is twice the amount of commands). The functions may refer to global data, local temporary data, local function parameter data, or object data (selectors). They may, additionally, indirectly refer to "hunk" data, which is stored outside of the SCI heap. Since the whole design is object oriented, functions may re-use or overload the functions of their superclasses.

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