/*
   4xMSAL shader

   Copyright (C) 2007 guest(r) - guest.r@gmail.com

   This program 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.

   This program 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 this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

*/

uniform sampler2D OGL2Texture;

void main()
{
	vec2 dx = vec2(1.0 / 4096.0, 0.0);
	vec2 dy = vec2(0.0, 1.0 / 2048.0);
	vec3 dt = vec3(1.0, 1.0, 1.0);

	vec3 c00, c02, c20, c22, u, d, r, l;
	float m1, m2;

	c00 = texture2D(OGL2Texture, gl_TexCoord[1].xy - dy).xyz;
	c20 = texture2D(OGL2Texture, gl_TexCoord[2].xy - dy).xyz;
	c02 = texture2D(OGL2Texture, gl_TexCoord[4].xy - dy).xyz;
	c22 = texture2D(OGL2Texture, gl_TexCoord[3].xy - dy).xyz;

	m1 = dot(abs(c00 - c22), dt) + 0.001;
	m2 = dot(abs(c02 - c20), dt) + 0.001;

	u = 0.5 * (m2 * (c00 + c22) + m1 * (c02 + c20)) / (m1 + m2);

	c00 = texture2D(OGL2Texture, gl_TexCoord[1].xy + dy).xyz;
	c20 = texture2D(OGL2Texture, gl_TexCoord[2].xy + dy).xyz;
	c02 = texture2D(OGL2Texture, gl_TexCoord[4].xy + dy).xyz;
	c22 = texture2D(OGL2Texture, gl_TexCoord[3].xy + dy).xyz;

	m1 = dot(abs(c00 - c22), dt) + 0.001;
	m2 = dot(abs(c02 - c20), dt) + 0.001;

	d = 0.5 * (m2 * (c00 + c22) + m1 * (c02 + c20)) / (m1 + m2);

	c00 = texture2D(OGL2Texture, gl_TexCoord[1].xy - dx).xyz;
	c20 = texture2D(OGL2Texture, gl_TexCoord[2].xy - dx).xyz;
	c02 = texture2D(OGL2Texture, gl_TexCoord[4].xy - dx).xyz;
	c22 = texture2D(OGL2Texture, gl_TexCoord[3].xy - dx).xyz;

	m1 = dot(abs(c00 - c22), dt) + 0.001;
	m2 = dot(abs(c02 - c20), dt) + 0.001;

	l = 0.5 * (m2 * (c00 + c22) + m1 * (c02 + c20)) / (m1 + m2);

	c00 = texture2D(OGL2Texture, gl_TexCoord[1].xy + dx).xyz;
	c20 = texture2D(OGL2Texture, gl_TexCoord[2].xy + dx).xyz;
	c02 = texture2D(OGL2Texture, gl_TexCoord[4].xy + dx).xyz;
	c22 = texture2D(OGL2Texture, gl_TexCoord[3].xy + dx).xyz;

	m1 = dot(abs(c00 - c22), dt) + 0.001;
	m2 = dot(abs(c02 - c20), dt) + 0.001;

	r = 0.5 * (m2 * (c00 + c22) + m1 * (c02 + c20)) / (m1 + m2);

	gl_FragColor.xyz = 0.25 * (u + d + r + l);
}