#version 430 core
layout (points) in;
layout (triangle_strip, max_vertices = 4) out;

out vec3 dField;
out float lum;

uniform vec2 lightPos;
uniform mat4 perpMat;
uniform vec2 radLum;

float isLHS (vec2 startV, vec2 testV)
{
    return sign( -startV.x * testV.y + startV.y * testV.x);
}
vec4 shiftCloser (vec4 v)
{ return vec4 (v.xy , v.z-0.0001 , v.w) ; }

void main()
{
vec4 p1 = vec4 (gl_in[0].gl_Position.xy,0,1);
vec4 p2 = vec4 (gl_in[0].gl_Position.zw,0,1);
if (isLHS (p1.xy - lightPos, p2.xy - lightPos) < 0)
{
    lum = radLum.y;
    float rad = radLum.x;

    vec4 p3 = vec4 (p1.xy,-0.5,1);
    vec4 p4 = vec4 (p2.xy,-0.5,1);

    vec2 d1 = p1.xy - lightPos;
    vec2 d2 = p2.xy - lightPos;
    
    vec4 a1 = shiftCloser( perpMat * p1 );
    vec4 a2 = shiftCloser( perpMat * p2 );
    vec4 a3 = shiftCloser( perpMat * p3 );
    vec4 a4 = shiftCloser( perpMat * p4 );
    
    dField = vec3( d1.x/rad, d1.y/rad, 0);
    gl_Position = a1; 
    EmitVertex();
    dField = vec3( d1.x/rad, d1.y/rad, 1);
    gl_Position = a3; 
    EmitVertex();
    dField = vec3( d2.x/rad, d2.y/rad, 0);
    gl_Position = a2; 
    EmitVertex();
    dField = vec3( d2.x/rad, d2.y/rad, 1);
    gl_Position = a4; 
    EmitVertex();
    
    EndPrimitive();
} else {}
}

//  //  void main()
//  //  {
//  //    vec4 frontL4 = worldMat * vec4(gl_in[0].gl_Position.xy, 0 ,1);
//  //    vec4 frontR4 = worldMat * vec4(gl_in[0].gl_Position.zw, 0 ,1);
//  //    vec2 frontL = frontL4.xy;
//  //    vec2 frontR = frontR4.xy;
//  //  
//  //      emitLine (frontR);
//  //      emitLine (frontL);
//  //    EndPrimitive();
//  //  }
//  gl_Position = perspective * worldMat * p4; EmitVertex();
//  gl_Position = perspective * worldMat * p3; EmitVertex();
//  gl_Position = perspective * worldMat * p7; EmitVertex();
//  gl_Position = perspective * worldMat * p8; EmitVertex();
//  gl_Position = perspective * worldMat * p5; EmitVertex();
//  gl_Position = perspective * worldMat * p3; EmitVertex();
//  gl_Position = perspective * worldMat * p1; EmitVertex();
//  gl_Position = perspective * worldMat * p4; EmitVertex();
//  gl_Position = perspective * worldMat * p2; EmitVertex();
//  gl_Position = perspective * worldMat * p7; EmitVertex();
//  gl_Position = perspective * worldMat * p6; EmitVertex();
//  gl_Position = perspective * worldMat * p5; EmitVertex();
//void emitLine (vec2 pa)
//{
//    gl_Position = vec4 (pa, 0, 1);
//    EmitVertex();
//    gl_Position = shift (vec4 (pa,0,1)); //vec4 (pa + (200 * (pa - lightPosa)), 0 , 1);
//    EmitVertex();
//}