LearnOpenGL/Shaders/pbr.fs

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#version 460 core
out vec4 FragColor;
in vec2 TexCoords;
in vec3 WorldPos;
in vec3 Normal;
uniform vec3 camPos;
uniform vec3 albedo;
uniform float metallic;
uniform float roughness;
uniform float ao;
uniform vec3 lightPositions[4];
uniform vec3 lightColors[4];
const float PI = 3.14159265359;
// ratio Refraction vs Reflection (F function)
vec3 fresnelSchlick (float cosTheta, vec3 F0)
{
return F0 + (1.0 - F0) * pow(clamp(1.0 - cosTheta, 0.0, 1.0), 5.0);
}
// Calculate Normal distribution (D function)
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;
}
// G function
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 N = normalize(Normal);
vec3 V = normalize(camPos - WorldPos);
vec3 F0 = vec3(0.04);
F0 = mix(F0, albedo, metallic);
// Calculate the light contributions of each light source
vec3 Lo = vec3(0.0);
for( int i = 0; i < 4; ++i)
{
vec3 L = normalize(lightPositions[i] - WorldPos);
vec3 H = normalize(V + L);
float distance = length(lightPositions[i] - WorldPos);
float attenuation = 1.0/ (distance*distance);
vec3 radiance = lightColors[i] * attenuation;
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 numerator = NDF * G * F;
float denominator = 4.0 * max(dot(N,V), 0.0) * max(dot(N, L), 0.0) + 0.0001;
vec3 specular = numerator /denominator;
float NdotL = max(dot(N,L), 0.0);
Lo += (kD * albedo / PI + specular) * radiance * NdotL;
}
// Calculate the ambient term and add it
vec3 ambient = vec3(0.03) * albedo * ao;
vec3 color = ambient + Lo;
// Gamma correct the result
color = color / (color + vec3(1.0));
color = pow(color, vec3(1.0/2.2));
FragColor = vec4(color, 1.0);
}