default.vert

#version 410

uniform mat4 MVP; // Projection * View * Model matrix
uniform mat4 MV;  // View * Model Matrix
uniform mat4 NM;  // Normal matrix
uniform int  NMU; // Use normal matrix

layout(location = 0) in vec3 POSITION;
layout(location = 1) in vec3 NORMAL;

out vec3 vPosition;
out vec3 vNormal;
out vec3 vEye;

void main() {
  vec4 pos4 = vec4(POSITION, 1.0);

  vPosition = vec3(MV * pos4);
  vEye      = normalize(-vPosition);

  if (NMU == 1)
    vNormal = normalize(vec3(NM * vec4(NORMAL, 0.0)));
  else
    vNormal = normalize(vec3(MV * vec4(NORMAL, 0.0)));

  gl_Position = MVP * pos4;
}

This shader is not used by libgk anymore!
Now there is a shader generator and shader manager for specific purposes/tasks

Check new version at: https://github.com/recp/libgk/tree/master/src/shader/glsl