guSprite2DInit

guSprite2DInit [Function]

Function

guSprite2DInit

Initializes a sprite data structure

Syntax

#include <ultra64.h>        /* gu.h */
void guSprite2DInit(
        uSprite *SpritePointer,
        void     *SourceImagePointer,
        void     *TlutPointer,
        int      Stride,
        int      SubImageWidth,
        int      SubImageHeight,
        int      SourceImageType,
        int      SourceImageBitSize,
        int      SourceImageOffsetS,
        int      SourceImageOffsetT);

Arguments

SpritePointer: Pointer to the resulting uSprite structure
SourceImagePointer: Pointer to the texture image base
TlutPointer: Pointer to color index
Stride: Base image texel width
SubImageWidth: Displayed image texel width
SubImageHeight: Displayed image texel height
SourceImageType: Texture image format; G_IM_FMT_RGBA (RGBA format); G_IM_FMT_YUV (YUV format); G_IM_FMT_CI (CI format); G_IM_FMT_IA (IA format); G_IM_FMT_I (I format)
SourceImageBitSize: Pixel component size; G_IM_SIZ_4b (4 bits per texel); G_IM_SIZ_8b (8 bits per texel); G_IM_SIZ_16b (16 bits per texel); G_IM_SIZ_32b (32 bits per texel)
SourceImageOffsetS: Offset from origin of base image to texel column
SourceImageOffsetT: Offset from origin of base image to texel row

Returned value

None.

Description

Initializes the Sprite structure according to the specified arguments for use with the sprite microcode.

Regarding the TlutPointer argument:: Set to NULL if not using CI images.
Regarding the SourceImageType argument:

G_IM_FMT_RGBA
Each texel comprises four elements of information: RGB (red, green, blue) and alpha (opacity).
G_IM_FMT_YUV
Each texel comprises a Y (intensity) component and a UV (color difference) component.
G_IM_FMT_CI
Each texel is comprised of index information specifying palette data.
G_IM_FMT_IA
Each texel is comprised of I (intensity) information and alpha information.
G_IM_FMT_I
Each texel is a texture with only I information. Since this is extremely compact, it is useful when only a few colors are being used.

The texture image format can be selected from among 10 types. Refer to the following table for valid combinations of format and size and select the most suitable format for the texture compression method and type.

G_IM_SIZ_ (Size)
4b 8b 16b 32b
G_IM_FMT_
(Format) RGBA -- -- X
(5/5/5/1) X
(8/8/8/8)
YUV -- -- X --
CI X X -- --
IA X
(3/1) X
(4/4) X
(8/8) --
I X X -- --
Regarding the SourceImageOffsetS, SourceImageOffsetT arguments:: These specify the staring position of the rectangular region displaying texels in the base image.

Note

We currently cannot guarantee operation of G_IM_FMT_YUV (YUV format). At the present time, this function is only useful for simply copying each argument into the appropriate location of the specified SpritePointer. Instead of using this function, you can directly initialize the sprite structure.

Comment

The uSprite structure looks like this:

typedef struct {
     void   *SourceImagePointer;
     void   *TlutPointer;
     short  Stride;
     short  SubImageWidth;
     short  SubImageHeight;
     char   SourceImageType;
     char   SourceImageBitSize;
     short  SourceImageOffsetS;
     short  SourceImageOffsetT;
     char   dummy[4]; 
} uSprite_t;
typedef union {
     uSprite_t      s;
     long long int  force_structure_alignment[3];
} uSprite;

Revision History

03/01/99 Completely rewritten.

		G_IM_SIZ_ (Size)
		4b	8b	16b	32b
G_IM_FMT_ (Format)	RGBA	--	--	X (5/5/5/1)	X (8/8/8/8)
	YUV	--	--	X	--
	CI	X	X	--	--
	IA	X (3/1)	X (4/4)	X (8/8)	--
	I	X	X	--	--