#version 330 compatibility
// make this 120 for the mac:

// lighting uniform variables -- these can be set once and left alone:
uniform float   uKa, uKd, uKs;   // coefficients of each type of lighting -- make sum to 1.0
uniform vec3    uColor;          // object color
uniform vec3    uSpecularColor;  // light color
uniform float   uShininess;      // specular exponent

// ellipse-equation uniform variables -- these should be set every time Display( ) is called:

uniform float   uSc, uTc;
uniform float   uRs, uRt;

// in variables from the vertex shader and interpolated in the rasterizer:

in  vec3  vN;              // normal vector
in  vec3  vL;              // vector from point to light
in  vec3  vE;              // vector from point to eye
in  vec2  vST;             // (s,t) texture coordinates


void
main( )
{
        vec3 Normal = normalize(vN);
        vec3 Light  = normalize(vL);
        vec3 Eye    = normalize(vE);
        float s = vST.s;
        float t = vST.t;

        // determine the color using the ellipse equation:

        vec3 myColor = uColor;
        if( ????? )
        {
                myColor = vec3( ????? );
        }

        // apply the per-fragmewnt lighting to myColor:

        vec3 ambient = uKa * myColor;

        float dd = max( dot(Normal,Light), 0. );       // only do diffuse if the light can see the point
        vec3 diffuse = uKd * dd * myColor;

        float ss = 0.;
        if( dot(Normal,Light) > 0. )          // only do specular if the light can see the point
        {
                vec3 ref = normalize(  reflect( -Light, Normal )  );
                ss = pow( max( dot(Eye,ref),0. ), uShininess );
        }
        vec3 specular = uKs * ss * uSpecularColor;
        gl_FragColor = vec4( ambient + diffuse + specular,  1. );
}