// ================
// Vertex shader:
// ================
#version 330 core
layout (location = 0) in vec3 position;
layout (location = 1) in vec3 normal;

out VS_OUT {
    vec3 normal;
} vs_out;

uniform mat4 projection;
uniform mat4 view;
uniform mat4 model;

void main()
{
    gl_Position = projection * view * model * vec4(position, 1.0f); 
    mat3 normalMatrix = mat3(transpose(inverse(view * model)));
    vs_out.normal = vec3(projection * vec4(normalMatrix * normal, 1.0));
}


// ================
// Fragment shader:
// ================
#version 330 core
out vec4 color;

void main()
{
    color = vec4(1.0f, 1.0f, 0.0f, 1.0f);
}


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

in VS_OUT {
    vec3 normal;
} gs_in[];

const float MAGNITUDE = 0.2f;

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

void main()
{
    GenerateLine(0); // First vertex normal
    GenerateLine(1); // Second vertex normal
    GenerateLine(2); // Third vertex normal
}