--- /dev/null
+#version 330
+
+#define mdot(x, y) (max(dot(x, y), 0.f))
+
+in vec3 worldPos, normal;
+in vec2 texCoords;
+
+uniform vec3 camPos;
+
+uniform sampler2D albedoMap;
+uniform sampler2D normalMap;
+uniform sampler2D metallicMap;
+uniform sampler2D roughnessMap;
+uniform sampler2D aoMap;
+
+out vec4 fragColor;
+
+uniform vec3 lightPositions[4];
+uniform vec3 lightColors[4];
+
+const float PI = 3.14159265359;
+
+vec3 fresnelSchlick(float cosTheta, vec3 F0) {
+ return F0 + (1.f - F0) * pow(1.f - cosTheta, 5.f);
+}
+
+float distributionGGX(vec3 N, vec3 H, float roughness) {
+ float a = roughness * roughness;
+ float NdotH = mdot(N, H);
+ float denom = (NdotH * NdotH) * ((a * a) - 1.f) + 1.f;
+ denom = PI * denom * denom;
+ return (a * a) / denom;
+}
+
+float geometrySchlickGGX(float NdotV, float roughness) {
+ float r = roughness + 1.f;
+ float k = (r * r) / 8.f;
+ return NdotV / (NdotV * (1.f - k) + k);
+}
+
+float geometrySmith(vec3 N, vec3 V, vec3 L, float roughness) {
+ float ggx1 = geometrySchlickGGX(mdot(N, L), roughness);
+ float ggx2 = geometrySchlickGGX(mdot(N, V), roughness);
+ return ggx1 * ggx2;
+}
+
+vec3 getNormalFromMap() {
+ vec3 tangentNormal = texture(normalMap, texCoords).xyz * 2.f - 1.f;
+ 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);
+}
+
+void main() {
+ vec3 albedo = pow(texture(albedoMap, texCoords).rgb, vec3(2.2));
+ vec3 normal = getNormalFromMap();
+ float metallic = texture(metallicMap, texCoords).r;
+ float roughness = texture(roughnessMap, texCoords).r;
+ float ao = texture(aoMap, texCoords).r;
+
+ vec3 N = normalize(normal);
+ vec3 V = normalize(camPos - worldPos);
+
+ vec3 F0 = mix(vec3(0.04), albedo, metallic);
+
+ // reflectance
+ vec3 Lo = vec3(0.f);
+ for (int i = 0; i < lightPositions.length(); i++) {
+ vec3 L = normalize(lightPositions[i] - worldPos);
+ vec3 H = normalize(V + L);
+
+ // calculate radiance
+ float dist = length(lightPositions[i] - worldPos);
+ float attenuation = 5.f / (dist * dist);
+ vec3 radiance = lightColors[i] * attenuation;
+
+ // cook-torrance brdf
+ vec3 F = fresnelSchlick(mdot(H, V), F0);
+ float NDF = distributionGGX(N, H, roughness);
+ float G = geometrySmith(N, V, L, roughness);
+
+ float denom = 4.f * mdot(N, V) * mdot(N, L);
+ vec3 specular = (NDF * G * F) / max(denom, 0.0000001);
+
+ vec3 kS = F; // fresnel = reflection ratio
+ vec3 kD = vec3(1.f) - kS;
+ kD *= 1.f - metallic;
+
+ Lo += (kD * albedo / PI + specular) * radiance * mdot(N, L);
+ }
+
+ vec3 ambient = vec3(0.03) * albedo * ao;
+ vec3 color = ambient + Lo;
+
+ color = color / (color + vec3(1.f)); // map to HDR
+ color = pow(color, vec3(1.f / 2.2)); // gamma correction
+
+ fragColor = vec4(color, 1.f);
+}