shader

#version 330 core

struct Material {
    sampler2D diffuse;
    sampler2D specular;
    sampler2D emission;
    float shininess;
};

struct DirLight {
    vec3 direction;

    vec3 ambient;
    vec3 diffuse;
    vec3 specular;
};

struct PointLight {
    vec3 position;

    float constant;
    float linear;
    float quadratic;

    vec3 ambient;
    vec3 diffuse;
    vec3 specular;
};
#define NR_POINT_LIGHTS 4

out vec4 FragColor;

in vec3 Normal;
in vec3 FragPos;

in vec2 TexCoords;

uniform vec3 objectColor;
uniform vec3 viewPos;

uniform Material material;
uniform DirLight dirLight;
uniform PointLight pointLights[NR_POINT_LIGHTS];
uniform int number_of_point_lights;

vec3 directional_light_calculation(DirLight light, vec3 normal, vec3 viewDir);
vec3 point_light_calculation(PointLight light, vec3 normal, vec3 fragPos, vec3 viewDir);

void main()
{
   vec3 output = vec3(0.0f);

   vec3 norm = normalize(Normal);
   vec3 viewDir = normalize(viewPos - FragPos);

   output += directional_light_calculation(dirLight, norm, viewDir);

   for (int i = 0; i < NR_POINT_LIGHTS; i++)
   {
       output += point_light_calculation(pointLights[i], norm, FragPos, viewDir);
   }

   FragColor = vec4(texture(material.emission, TexCoords) + output, 1.0f);

}

vec3 directional_light_calculation(DirLight light, vec3 normal, vec3 viewDir){

     vec3 lightDir = normalize(-light.direction);

    float diff = max(dot(normal, lightDir), 0.0);

    vec3 reflectDir = reflect(-lightDir, normal);
    float spec = pow(max(dot(viewDir, reflectDir), 0.0), material.shininess);

    vec3 ambient = light.ambient * vec3(texture(material.diffuse, TexCoords));
    vec3 diffuse = light.diffuse * diff * vec3(texture(material.diffuse, TexCoords));
    vec3 specular = light.specular * spec * vec3(texture(material.specular, TexCoords));
    return ambient + diffuse + specular;

}

vec3 point_light_calculation(PointLight light, vec3 normal, vec3 fragPos, vec3 viewDir){

    vec3 lightDir = normalize(light.position - fragPos);

    float diff = max(dot(normal, lightDir), 0.0);

    vec3 reflectDir = reflect(-lightDir, normal);
    float spec = pow(max(dot(viewDir, reflectDir), 0.0), material.shininess);

    float distance = length(light.position - fragPos);
    float attenuation = 1.0 / (light.constant + light.linear * distance + light.quadratic * (distance * distance));

    vec3 ambient = light.ambient * vec3(texture(material.diffuse, TexCoords));
    vec3 diffuse = light.diffuse * diff * vec3(texture(material.diffuse, TexCoords));
    vec3 specular = light.specular * spec * vec3(texture(material.specular, TexCoords));
    ambient *= attenuation;
    diffuse *= attenuation;
    specular *= attenuation;
    return ambient + diffuse + specular;

}