guAlign [Function]

Function

guAlign

Creates a modeling matrix for rotation around an arbitrary axis (aligned, fixed-point)

Syntax

#include <ultra64.h>        /* gu.h */
void guAlign(Mtx *m, float a, float x, float y, float z);

Arguments

m

Pointer to 4x4 matrix resulting from calculation

a

Angle of rotation (in degrees) around an arbitrary axis

x

x component of axis of rotation

y

y component of axis of rotation

z

z component of axis of rotation

Returned value

None

Description

This macro performs an alignment process (in which the arbitrary axis represented by the line passing through the origin and a point (x, y, z) is rotated so it points in the same direction as the negative Z axis), and then returns a modeling matrix to the structure indicated by m for use in rotating by an angle of a degrees in the positive direction around this arbitrary axis. The result of calling this macro is the creation of a modeling matrix like the one shown below. Note that a unit matrix is returned when h = 0.

(* Note that the values (x,y,z) here are normalized inside the function)

For a detailed explanation about the fixed-point format, see gSPMatrix. Floating-point is handled using guAlignF.

Note

The vector does not have to be normalized ahead of time. This is done inside the function. However, when = 0 the operation of this macro cannot be guaranteed.

Comment

The Mtx structure is shown below:

typedef long  Mtx_t[4][4];
typedef union {
     Mtx_t          m;
     long long int  force_structure_alignment;
} Mtx;

See also

gSPMatrix, guAlignF, guRotate, guRotateF, guScale, guScaleF, guTranslate, and guTranslateF

Revision history

03/01/99 Completely rewritten.