#version 330 core

// Vertex shader decides where each vertex is in 3D space

// --- INPUTS ---
// Comes directly from the vertex buffer
layout(location = 0) in vec3 aPosition; // Raw 3D position
layout(location = 1) in vec3 aNormal; // The direction perpendicular to the surface
layout(location = 2) in vec2 aTexCoord; // The U,V texture coordinates
layout(location = 3) in vec3 aTangent; // Tangent vector for normal mapping
layout(location = 4) in vec3 aBitangent; // Bitangent vector for normal mapping

// --- OUTPUTS ---
// We can pass data to the fragment shader through these
out vec3 FragPos;
out vec3 Normal;
out vec2 TexCoord;
out mat3 vTBN;

// --- UNIFORMS ---
// These are matrices that help transform our vertices
uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;

void main(void)
{
    vec3 T = normalize(vec3(model * vec4(aTangent, 0.0)));
    vec3 B = normalize(vec3(model * vec4(aBitangent, 0.0)));
    vec3 N = normalize(vec3(model * vec4(aNormal, 0.0)));
    
    vTBN = mat3(T, B, N);
    
    // 1. Calculate World Position
    FragPos = vec3(model * vec4(aPosition, 1.0));

    // 2. Calculate Normal
    Normal = mat3(transpose(inverse(model))) * aNormal;
    
    // 3. Pass Texture Coordinates
    TexCoord = aTexCoord;

    // 4. Calculate Final Position
    gl_Position = projection * view * vec4(FragPos, 1.0);
}