/*
===========================================================================
Copyright (C) 1999-2005 Id Software, Inc.
Copyright (C) 2006 Robert Beckebans <trebor_7@users.sourceforge.net>

This file is part of XreaL source code.

XreaL source code 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.

XreaL source code 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 XreaL source code; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
===========================================================================
*/

// r_shadows.c
#include "r_local.h"

/*
  for a projection shadow:

  point[x] += light vector * ( z - shadow plane )
  point[y] +=
  point[z] = shadow plane

  1 0 light[x] / light[z]
*/

shadowState_t sh;

/*
=================
RB_ProjectionShadowDeform
=================
*/
void RB_ProjectionShadowDeform(void)
{
	float          *xyz;
	int             i;
	float           h;
	vec3_t          ground;
	vec3_t          light;
	float           groundDist;
	float           d;
	vec3_t          lightDir;

	xyz = (float *)tess.xyz;

	ground[0] = backEnd.or.axis[0][2];
	ground[1] = backEnd.or.axis[1][2];
	ground[2] = backEnd.or.axis[2][2];

	groundDist = backEnd.or.origin[2] - backEnd.currentEntity->e.shadowPlane;

	VectorCopy(backEnd.currentEntity->lightDir, lightDir);
	d = DotProduct(lightDir, ground);
	// don't let the shadows get too long or go negative
	if(d < 0.5)
	{
		VectorMA(lightDir, (0.5 - d), ground, lightDir);
		d = DotProduct(lightDir, ground);
	}
	d = 1.0 / d;

	light[0] = lightDir[0] * d;
	light[1] = lightDir[1] * d;
	light[2] = lightDir[2] * d;

	for(i = 0; i < tess.numVertexes; i++, xyz += 4)
	{
		h = DotProduct(xyz, ground) + groundDist;

		xyz[0] -= light[0] * h;
		xyz[1] -= light[1] * h;
		xyz[2] -= light[2] * h;
	}
}
