====== Fundamentals of Cel Manipulation ======


----

This section summarizes some background information about 3DO cels. It discusses:

  * [[:documentation:development:opera:pf25:ppgfldr:smmfldr:gspfldr:#xref34593|The CCB Structure]]
  * [[:documentation:development:opera:pf25:ppgfldr:smmfldr:gspfldr:#xref40214|Frequently Accessed CCB Fields]]

==== For More Information ====

To successfully work with cels, it is essential you read the relevant chapters in the //3DO Graphics Programmer's Guide//.



===== The CCB Structure =====

The example below shows the structure definition for a CCB, taken from graphics.h (part of the 3DO development environment #include files). The comments explaining the different types are not in the header file, but are included here for your information.

**Caution:** The datatypes of the different fields differ; a common source of programming problems.

**Example 1:** //The CCB structure//

''%%%%''

<code>
typedef struct CCB {
    uint32 ccb_Flags;
    struct CCB *ccb_NextPtr;
    CelData *ccb_SourcePtr;
    void *ccb_PLUTPtr;

    Coord ccb_XPos;                        /*16.16 (not int32!)*/
    Coord ccb_YPos;                        /*16.16 (not int32!)*/
    int32 ccb_HDX;                        /*12.20*/
    int32 ccb_HDY;                        /*12.20*/
    int32 ccb_VDX;                        /*16.16*/
    int32 ccb_VDY;                        /*16.16*/
    int32 ccb_HDDX;                        /*12.20, increment for drawing 
*/
    int32 ccb_HDDY;                        /*12.20, increment for drawing 
*/
    uint32 ccb_PIXC;                        /*P-Mode bit*/

    uint32 ccb_PRE0;                        /*preamble*/
    uint32 ccb_PRE1;                        /**preamble*/

    int32 ccb_Width;                    /*don't change, change position 
instead*
    int32 ccb_Height;                    /*don't change, change position 
instead*/
} CCB;
</code>
==== For More Information ====

A detailed discussion of the CCB is provided in Chapter 5, "Using the Cel Engine," of the //3DO Portfolio Graphics Programmer's Guide//.



===== Frequently Accessed CCB Fields =====

About one-third of the fields in the CCB pertain to the cel's basic source data.

  * ''%%ccb_SourcePtr%%''-a pointer to the data
  * ''%%ccb_PLUTPtr%%''-a pointer to the palette
  * ''%%ccb_PRE0%%'' and ''%%ccb_PRE1%%''-two possible "preamble words" that store extra data in some cel formats
  * ''%%ccb_Width%%'' and ''%%ccb_Height%%''-the width and height of the source data
  * ''%%ccb_XPos%%'' and ''%%ccb_YPos%%''-the location of the upper-left corner of the cel

You can do a lot of cel manipulation by directly setting the values of the fields. For example, you can use a simple graphic of two parallel lines to create a laser beam effect. The program stretches the parallel lines from the origin to the bottom left and right corners of the screen by changing the value of ''%%ccB_Width%%'' and ''%%ccB_Height%%''. This gives the illusion of the beam in the jsanimation program.