/*
 * Wolfenstein: Enemy Territory GPL Source Code
 * Copyright (C) 1999-2010 id Software LLC, a ZeniMax Media company.
 * Copyright (C) 2010-2011 Robert Beckebans <trebor_7@users.sourceforge.net>
 *
 * ET: Legacy
 * Copyright (C) 2012-2024 ET:Legacy team <mail@etlegacy.com>
 *
 * This file is part of ET: Legacy - http://www.etlegacy.com
 *
 * ET: Legacy 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 3 of the License, or
 * (at your option) any later version.
 *
 * ET: Legacy 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 ET: Legacy. If not, see <http://www.gnu.org/licenses/>.
 *
 * In addition, Wolfenstein: Enemy Territory GPL Source Code is also
 * subject to certain additional terms. You should have received a copy
 * of these additional terms immediately following the terms and conditions
 * of the GNU General Public License which accompanied the source code.
 * If not, please request a copy in writing from id Software at the address below.
 *
 * id Software LLC, c/o ZeniMax Media Inc., Suite 120, Rockville, Maryland 20850 USA.
 */
/**
 * @file renderer2/tr_shadows.c
 */

#include "tr_local.h"

shadowState_t shadowState;

/**
 * @brief RB_ProjectionShadowDeform
 *
 * @note   for a projection shadow:
 *
 * point[x] += light vector * ( z - shadow plane )
 * point[y] +=
 * point[z] = shadow plane
 *
 * 1 0 light[x] / light[z]
 */
void RB_ProjectionShadowDeform(void)
{
	float        *xyz = (float *)tess.xyz;
	unsigned int i;
	float        h;
	vec3_t       ground;
	vec3_t       light;
	float        groundDist;
	float        d;
	vec3_t       lightDir;

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

	groundDist = backEnd.orientation.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 < 0.5f)
	{
		VectorMA(lightDir, (0.5f - d), ground, lightDir);
		d = DotProduct(lightDir, ground);
	}
	d = 1.0f / 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;
	}
}
