GXBegin

C Specification

#include <revolution/gx.h>

void GXBegin(GXPrimitive type, GXVtxFmt vtxfmt, u16 nverts);

Arguments

type

specifies the primitive type
Accepted values are:

Name	Primitive Type
`GX_POINTS`	Points
`GX_LINES`	Lines
`GX_LINESTRIP`	Line strip
`GX_TRIANGLES`	Triangles
`GX_TRIANGLESTRIP`	Triangle Strips
`GX_TRIANGLEFAN`	Triangle fans
`GX_QUADS`	quad

vtxfmt Specifies the vertex attribute format.
This format is set using GXSetVtxAttrFmt before calling GXBegin. The following values are acceptable: GX_VTXFMT0, GX_VTXFMT1, GX_VTXFMT2, GX_VTXFMT3, GX_VTXFMT4, GX_VTXFMT5, GX_VTXFMT6, and GX_VTXFMT7.

nverts Specifies the number of vertices between GXBegin and GXEnd.
The maximum number of vertices is 65,536. The minimum number of vertices is the same as the minimum number of required primitive types.

Return Values

None.

Description

Use this function to begin drawing a graphics primitive. To draw a graphics primitive, a stream of vertex data matching the description of both GXSetVtxDesc and GXSetVtxAttrFmt is enclosed between GXBegin/GXEnd pairs.

GXClearVtxDesc(); GXSetVtxDesc(GX_VA_POS, GX_INDEX8); GXSetVtxAttrFmt(GX_VTXFMT0, GX_VA_POS, GX_POS_XYZ, GX_F32, 0); GXSetArray(GX_VA_POS, &myverts[0], sizeof(f32));

GXBegin(GX_TRIANGLES, GX_VTXFMT0, 6); GXPosition1u8(0); // tri 0, vertex 0, 8b index GXPosition1u8(1); // tri 0, vertex 1, 8b index GXPosition1u8(2); // tri 0, vertex 2, 8b index GXPosition1u8(3); // tri 1, vertex 0, 8b index GXPosition1u8(4); // tri 1, vertex 1, 8b index GXPosition1u8(5); // tri 1, vertex 2, 8b index GXEnd();

The number of vertices between GXBegin and GXEnd must match that specified by the nverts argument. The type of the primitive will determine the minimum number of vertices required. For example, a GX_TRIANGLES primitive must have at least three vertices.


Primitives for which the vertex order is clockwise, as seen from the viewpoint, are handled as front-facing.

As a rule, GX functions other than vertex stream functions (GXPosition,GXNormal,GXColor,GXTexCoord,GXMatrixIndex) cannot be called between GXBegin and GXEnd.


See Also

GXEnd
 GXClearVtxDesc
 GXSetVtxDescv
 GXSetVtxAttrFmt
 GXSetVtxAttrFmtv
 GXSetArray
 GXPosition
 GXNormal
 GXColor
 GXTexCoord
 GXMatrixIndex
Revision History

2007/01/18 Revised the description. 
2006/03/01 Initial version.

CONFIDENTIAL