lookat.c
2.19 KB
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/**************************************************************************
* *
* Copyright (C) 1994, Silicon Graphics, Inc. *
* *
* These coded instructions, statements, and computer programs contain *
* unpublished proprietary information of Silicon Graphics, Inc., and *
* are protected by Federal copyright law. They may not be disclosed *
* to third parties or copied or duplicated in any form, in whole or *
* in part, without the prior written consent of Silicon Graphics, Inc. *
* *
**************************************************************************/
#include "guint.h"
void guLookAtF(float mf[4][4], float xEye, float yEye, float zEye,
float xAt, float yAt, float zAt,
float xUp, float yUp, float zUp)
{
float len, xLook, yLook, zLook, xRight, yRight, zRight;
guMtxIdentF(mf);
xLook = xAt - xEye;
yLook = yAt - yEye;
zLook = zAt - zEye;
/* Negate because positive Z is behind us: */
len = -1.0 / sqrtf (xLook*xLook + yLook*yLook + zLook*zLook);
xLook *= len;
yLook *= len;
zLook *= len;
/* Right = Up x Look */
xRight = yUp * zLook - zUp * yLook;
yRight = zUp * xLook - xUp * zLook;
zRight = xUp * yLook - yUp * xLook;
len = 1.0 / sqrtf (xRight*xRight + yRight*yRight + zRight*zRight);
xRight *= len;
yRight *= len;
zRight *= len;
/* Up = Look x Right */
xUp = yLook * zRight - zLook * yRight;
yUp = zLook * xRight - xLook * zRight;
zUp = xLook * yRight - yLook * xRight;
len = 1.0 / sqrtf (xUp*xUp + yUp*yUp + zUp*zUp);
xUp *= len;
yUp *= len;
zUp *= len;
mf[0][0] = xRight;
mf[1][0] = yRight;
mf[2][0] = zRight;
mf[3][0] = -(xEye * xRight + yEye * yRight + zEye * zRight);
mf[0][1] = xUp;
mf[1][1] = yUp;
mf[2][1] = zUp;
mf[3][1] = -(xEye * xUp + yEye * yUp + zEye * zUp);
mf[0][2] = xLook;
mf[1][2] = yLook;
mf[2][2] = zLook;
mf[3][2] = -(xEye * xLook + yEye * yLook + zEye * zLook);
mf[0][3] = 0;
mf[1][3] = 0;
mf[2][3] = 0;
mf[3][3] = 1;
}
void guLookAt (Mtx *m, float xEye, float yEye, float zEye,
float xAt, float yAt, float zAt,
float xUp, float yUp, float zUp)
{
Matrix mf;
guLookAtF(mf, xEye, yEye, zEye, xAt, yAt, zAt, xUp, yUp, zUp);
guMtxF2L(mf, m);
}