/*
*   Fragment shader to perform "angle-of-incidence" based shading: points near
*       "the edge" of an object will be more bright and more solid than points
*       near "the center" of the object. In reality, we use the dot product
*       between the viewing vector and the surface normal to determine this 
*       weight. With specular lighting, can give the object a glassy look.
*
*   Alexandri Zavodny, Fall 2010 
*       for CSE 40166/60166 Computer Graphics, University of Notre Dame
*/

varying vec4 theColor;
varying vec3 theNormal;
varying vec3 dirToLight;
varying vec4 normalInDeviceCoords;

void main()
{
    float mag = 1.0 - dot(normalize(normalInDeviceCoords), vec4(0.0,0.0,-1.0,0.0));
    //Uncomment this line to get a sharper falloff!
    //mag = mag*mag;

    float specularIntensity = max(dot(normalize(gl_LightSource[0].halfVector.xyz), theNormal), 0.0);
    vec4 specularColor = vec4(1.0,1.0,1.0,1.0);
    vec4 specularComponent = pow(specularIntensity, 50.0) * specularColor;

    float lc = dot(dirToLight, theNormal);
    gl_FragColor = clamp(specularComponent + vec4(mag, mag, mag, mag), 0.0, 1.0);
}