/* -------------------------------------------------------------------------------

Copyright (C) 1999-2007 id Software, Inc. and contributors.
For a list of contributors, see the accompanying CONTRIBUTORS file.

This file is part of GtkRadiant.

GtkRadiant is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

GtkRadiant is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GtkRadiant; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

----------------------------------------------------------------------------------

This code has been altered significantly from its original form, to support
several games based on the Quake III Arena engine, in the form of "Q3Map2."

------------------------------------------------------------------------------- */



/* marker */
#define BRUSH_PRIMIT_C



/* dependencies */
#include "q3map2.h"



/* -------------------------------------------------------------------------------

functions

------------------------------------------------------------------------------- */

/*
ComputeAxisBase()
computes the base texture axis for brush primitive texturing
note: ComputeAxisBase here and in editor code must always BE THE SAME!
warning: special case behaviour of atan2( y, x ) <-> atan( y / x ) might not be the same everywhere when x == 0
rotation by (0,RotY,RotZ) assigns X to normal
*/

void ComputeAxisBase(vec3_t normal, vec3_t texX, vec3_t texY)
{
	vec_t           RotY, RotZ;


	/* do some cleaning */
	if(fabs(normal[0]) < 1e-6)
		normal[0] = 0.0f;
	if(fabs(normal[1]) < 1e-6)
		normal[1] = 0.0f;
	if(fabs(normal[2]) < 1e-6)
		normal[2] = 0.0f;

	/* compute the two rotations around y and z to rotate x to normal */
	RotY = -atan2(normal[2], sqrt(normal[1] * normal[1] + normal[0] * normal[0]));
	RotZ = atan2(normal[1], normal[0]);

	/* rotate (0,1,0) and (0,0,1) to compute texX and texY */
	texX[0] = -sin(RotZ);
	texX[1] = cos(RotZ);
	texX[2] = 0;

	/* the texY vector is along -z (t texture coorinates axis) */
	texY[0] = -sin(RotY) * cos(RotZ);
	texY[1] = -sin(RotY) * sin(RotZ);
	texY[2] = -cos(RotY);
}
