/*
 Copyright (c) 2013 yvt
 
 This file is part of OpenSpades.
 
 OpenSpades 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.
 
 OpenSpades 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 OpenSpades.  If not, see <http://www.gnu.org/licenses/>.
 
 */


uniform mat4 projectionViewMatrix;
uniform mat4 viewMatrix;
uniform vec3 rightVector;
uniform vec3 upVector;

uniform float fogDistance;

attribute vec3 positionAttribute;
attribute vec2 texCoordAttribute;
attribute vec4 colorAttribute;

varying vec4 color;
varying vec2 texCoord;
varying vec4 fogDensity;

void main() {
	vec3 pos = positionAttribute.xyz;
	
	gl_Position = projectionViewMatrix * vec4(pos,1.);
	
	color = colorAttribute;
	
	texCoord = texCoordAttribute;
	
	// fog.
	// cannot gamma correct because sprite may be
	// alpha-blended.
	vec4 viewPos = viewMatrix * vec4(pos,1.);
	float distance = length(viewPos.xyz) / fogDistance;
	distance = clamp(distance, 0., 1.);
	fogDensity = vec4(distance);
	fogDensity = pow(fogDensity, vec4(1., .9, .7, 1.));
	fogDensity *= fogDensity; // FIXME
}