Transforming normals along with vertex? (GLSL)

Question

So, I got a model matrix (Via uniform variable) in the shader, is there any way to use the model matrix to transform the normal of a vertex that has been transformed with glm::transform/rotate?

If you want, here is the code:

VERTEX SHADER:

#version 330 core

layout(location = 0) in vec3 vertexPosition_modelspace;
layout(location = 1) in vec3 vertexColor;
layout(location = 2) in vec2 vertexUV;
layout(location = 3) in vec3 vertexNormal;

out vec3 Normal;
out vec3 fragmentColor;
out vec3 vertPos;
out vec2 UV;

uniform mat4 MVP;

void main(){
    gl_Position =  MVP * vec4(vertexPosition_modelspace,1.0f);
    UV = vertexUV;
    fragmentColor = vertexColor;
    vertPos = vertexPosition_modelspace;
    Normal = vertexNormal;
}

FRAGMENT SHADER:

#version 330 core

in vec3 Normal;
in vec3 fragmentColor;
in vec3 vertPos;
in vec2 UV;

out vec3 color;

uniform sampler2D textureSampler;
uniform mat4 Model;

void main(){
    vec3 lightPos = vec3(1, 1, 1);
    mat3 normalMatrix = transpose(inverse(mat3(Model))); // I think this line could do it, but it doesn't seem to work.
    vec3 normal = normalize(normalMatrix * Normal);
    vec3 fragPosition = vec3(Model * vec4(vertPos, 1));
    vec3 surfaceToLight = lightPos - fragPosition;

    float brightness = dot(normal, surfaceToLight) / (length(surfaceToLight) * length(normal));
    brightness = clamp(brightness, 0.2, 1);

    color = vec3(brightness * 1 * (texture(textureSampler, UV).rgb * fragmentColor));

}

Answer 1

Managed to fix it:

VERTEX SHADER:

#version 330 core

layout(location = 0) in vec3 vertexPosition_modelspace;
layout(location = 1) in vec3 vertexColor;
layout(location = 2) in vec2 vertexUV;
layout(location = 3) in vec3 vertexNormal;

out vec3 Normal;
out vec3 fragmentColor;
out vec4 vertPos;
out vec2 UV;
out mat4 mvp;

uniform mat4 MVP;

void main(){
    gl_Position =  MVP * vec4(vertexPosition_modelspace,1.0f);
    UV = vertexUV;
    fragmentColor = vertexColor;
    vertPos = MVP * vec4(vertexPosition_modelspace,1.0f);
    Normal = vertexNormal;
    mvp = MVP;
}

FRAGMENT SHADER:

#version 330 core

in vec3 Normal;
in vec3 fragmentColor;
in vec4 vertPos;
in vec2 UV;
in mat4 mvp;

out vec3 color;

uniform sampler2D textureSampler;
uniform mat4 Model;
uniform mat4 lmvp;

void main(){
    vec4 lightPos = lmvp * vec4(-0.5, 0.5, -0.5, 1);
    mat3 normalMatrix = transpose(inverse(mat3(Model)));
    vec3 normal = normalize(normalMatrix * Normal);
    vec3 fragPosition = vec3(Model * vec4(vertPos.xyz, 1));
    vec3 surfaceToLight = lightPos.xyz - fragPosition;

    float brightness = dot(normal, surfaceToLight) / (length(surfaceToLight) * length(normal));
    brightness = clamp(brightness, 0.2, 1);

    color = vec3(brightness * 1 * (texture(textureSampler, UV).rgb * fragmentColor));
}