//
// VS.txt is distributed under the FreeBSD License
//
// Copyright (c) 2012, Carlos Rafael Gimenes das Neves
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met: 
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer. 
// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution. 
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
// ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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// The views and conclusions contained in the software and documentation are those
// of the authors and should not be interpreted as representing official policies, 
// either expressed or implied, of the FreeBSD Project.
//
// http://carlosrafaelgn.com.br/WebGL/VS.txt
//
uniform mat4 modelViewProjectionMatrix, normalMatrix;
uniform vec3 lightDirection;
uniform bool useLight;
uniform float diffuseLightIntensity, ambientLightIntensity;

attribute vec4 attribPos; //0
attribute vec3 attribNormal; //1
attribute vec4 attribColor; //2

varying vec4 color;

void main()
{
	//calcula a posição de saída do vértice
	gl_Position = modelViewProjectionMatrix * attribPos;

	//calcula a cor do vértice, utilizando o algoritmo abaixo, porém em uma linha
	//em seguida, envia a cor para o próximo shader
	/*if (useLight) {
		//
		//NÃO precisaria normalizar novamente o vetor normal caso fosse possível
		//GARANTIR que a matriz utilizada para criar normalMatrix não contém
		//NENHUM tipo de redimensionamento! Infelizmente não pode ignorar as matrizes
		//de redimensionamento na hora de criar a matriz normal, pois elas alteram a
		//posição dos pontos, o que altera o ângulo das superfícies!
		//
		vec4 transNormal = normalize(normalMatrix * attribNormal.xyzx);
		float diffuse = max(dot(transNormal.xyz, lightDirection), 0.0);
		vec2 tmp = vec2((diffuseLightIntensity * diffuse) + ambientLightIntensity, 1.0);
		color = attribColor.rgba * tmp.xxxy;
	} else {
		color = attribColor;
	}*/
	color = (useLight ? (attribColor.rgba * vec2((diffuseLightIntensity * max(dot(normalize(normalMatrix * attribNormal.xyzx).xyz, lightDirection), 0.0)) + ambientLightIntensity, 1.0).xxxy) : attribColor);
}