PBR.frag

#version 330 core
out vec4 FragColor;
in vec2 TexCoords;
in vec3 WorldPos;
in vec3 Normal;

uniform vec3 camPos;

uniform vec3 lightPos;
const float PI = 3.14159265359;
struct Material {
//    //vec3 ambient;//环境光颜色在几乎所有情况下都等于漫反射颜色
//     sampler2D diffuse;
//    //vec3 diffuse;
//    sampler2D  specular;
//    float shininess;
    sampler2D albedoMap;
    sampler2D normalMap;
    sampler2D metallicMap;
    sampler2D roughnessMap;
    sampler2D aoMap;
}; 
struct Light {
    vec3 position;

    vec3 ambient;
    vec3 diffuse;
    vec3 specular;
};
//uniform Light light;
uniform Material material;
//uniform vec4 ourColor; 

vec3 getNormalFromMap()
{
    vec3 tangentNormal = texture(material.normalMap, TexCoords).xyz * 2.0 - 1.0;

    vec3 Q1  = dFdx(WorldPos);
    vec3 Q2  = dFdy(WorldPos);
    vec2 st1 = dFdx(TexCoords);
    vec2 st2 = dFdy(TexCoords);

    vec3 N   = normalize(Normal);
    vec3 T  = normalize(Q1*st2.t - Q2*st1.t);
    vec3 B  = -normalize(cross(N, T));
    mat3 TBN = mat3(T, B, N);

    return normalize(TBN * tangentNormal);
}
vec3 fresnelSchlick(float cosTheta, vec3 F0)
{
    return F0 + (1.0 - F0) * pow(clamp(1.0 - cosTheta, 0.0, 1.0), 5.0);
} 
float DistributionGGX(vec3 N, vec3 H, float roughness)
{
    float a      = roughness*roughness;
    float a2     = a*a;
    float NdotH  = max(dot(N, H), 0.0);
    float NdotH2 = NdotH*NdotH;

    float num   = a2;
    float denom = (NdotH2 * (a2 - 1.0) + 1.0);
    denom = PI * denom * denom;

    return num / denom;
}

float GeometrySchlickGGX(float NdotV, float roughness)
{
    float r = (roughness + 1.0);
    float k = (r*r) / 8.0;

    float num   = NdotV;
    float denom = NdotV * (1.0 - k) + k;

    return num / denom;
}
float GeometrySmith(vec3 N, vec3 V, vec3 L, float roughness)
{
    float NdotV = max(dot(N, V), 0.0);
    float NdotL = max(dot(N, L), 0.0);
    float ggx2  = GeometrySchlickGGX(NdotV, roughness);
    float ggx1  = GeometrySchlickGGX(NdotL, roughness);

    return ggx1 * ggx2;
} 
void main()
{
    vec3 albedo     = pow(texture( material.albedoMap, TexCoords).rgb, vec3(2.2));
    vec3 Normal     = getNormalFromMap();
    float metallic  = texture(material.metallicMap, TexCoords).r;
    float roughness = texture(material.roughnessMap, TexCoords).r;
    //float ao        = texture(material.aoMap, TexCoords).r;
    float ao=1;//先设置为全白
    vec3 N = normalize(Normal); 
    vec3 V = normalize(camPos - WorldPos);
    vec3 F0 = vec3(0.04); 
    F0 = mix(F0, albedo, metallic);
    vec3 Lo = vec3(0.0);//辐照度
      vec3 L = normalize(lightPos - WorldPos);
        vec3 H = normalize(V + L);
        float distance    = length(lightPos- WorldPos);
        float attenuation = 1.0 / (distance * distance);
        vec3 radiance     = vec3(1.0) * attenuation;        

        // cook-torrance brdf
        float NDF = DistributionGGX(N, H, roughness);        
        float G   = GeometrySmith(N, V, L, roughness);      
        vec3 F    = fresnelSchlick(max(dot(H, V), 0.0), F0);       

        vec3 kS = F;
        vec3 kD = vec3(1.0) - kS;
        kD *= 1.0 - metallic;     

        vec3 nominator    = NDF * G * F;
        float denominator = 4.0 * max(dot(N, V), 0.0) * max(dot(N, L), 0.0) + 0.001; 
        vec3 specular     = nominator / denominator;

        // add to outgoing radiance Lo
        float NdotL = max(dot(N, L), 0.0);                
        Lo += (kD * albedo / PI + specular) * radiance * NdotL;   vec3 ambient = vec3(0.04) * albedo * ao;
    vec3 color   = /*ambient*/ + Lo;  
    //gamma矫正
    color = color / (color + vec3(1.0));
    color = pow(color, vec3(1.0/2.2)); 
    FragColor =vec4(color,1);
}