#version 430 compatibility 
layout(location = 0) in vec3 vertexPosition;
layout(location = 1) in vec3 vertexNormal;

out vec3 interpNormal;
out vec3 fragPos;
out vec3 TexCoords;
out vec3 incident;
out float v_fresnel;
uniform vec3 viewPos;


// Indices of refraction
const float Air = 1.0;
const float Glass = 4; //1.51714;//4

// Air to glass ratio of the indices of refraction (Eta)
const float Eta = Air / Glass;

// see http://en.wikipedia.org/wiki/Refractive_index Reflectivity
const float R0 = ((Air - Glass) * (Air - Glass)) / ((Air + Glass) * (Air + Glass));



uniform mat4 modelMatrix;
uniform mat4 modelViewProjectionMatrix;
layout (binding = 0) uniform samplerCube tex_map;
void main()
{

	vec4 vertex = modelMatrix * vec4( vertexPosition, 1.0 );
	vec4 camera = vec4( viewPos, 1.0 );
	incident = normalize( vec3( vertex - camera ) );
	v_fresnel = R0 + (1.0 - R0) * pow( (1.0 - dot( -incident, vertexNormal ) ), 5.0);
	interpNormal = mat3(transpose(inverse(modelMatrix))) * vertexNormal;
	fragPos = (modelMatrix * vec4(vertexPosition, 1.0)).xyz;
	gl_Position = modelViewProjectionMatrix * vec4(vertexPosition, 1.0);
	 
}