Fundamentals of Cel Manipulation

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

The CCB Structure
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

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;

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.