#version 330 core
layout(triangles) in;
layout(line_strip, max_vertices = 6) out;

in VS_OUT {
    vec3 normal;
} gs_in[];

uniform mat4 proj;

const float MAGNITUDE = 0.4;

void generate_line(int index)
{
    gl_Position = proj*gl_in[index].gl_Position;
    EmitVertex();
    gl_Position = proj*(gl_in[index].gl_Position+
                              vec4(gs_in[index].normal, 0.0)*MAGNITUDE);
    EmitVertex();
    EndPrimitive();
}

void main(void)
{
    /*
    vec4 center = (gl_in[0].gl_Position+
                   gl_in[1].gl_Position+
                   gl_in[2].gl_Position)/3.0;
    vec4 end = center+vec4(((gs_in[0].normal+
                             gs_in[1].normal+
                             gs_in[2].normal)/3.0),
                           0.0)*MAGNITUDE;
    gl_Position = proj*center;
    EmitVertex();
    gl_Position = proj*end;
    EmitVertex();
    EndPrimitive();
    */
    generate_line(0);
    generate_line(1);
    generate_line(2);
}