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#version 410 core
out vec4 FragColor;
layout(location = 0) in vec3 fragWorldPos;
layout(location = 1) in vec3 fragNormal;
layout(location = 2) in vec2 fragTexCoords;
struct PointLight {
vec4 position;
vec4 color;
};
// --- Uniforms
// Material properties
uniform PBR_Params {
uniform vec3 albedo;
uniform float metallic;
uniform float roughness;
uniform float ao;
} pbr;
// Lights data
#define NUM_POINT_LIGHTS 4
uniform Scene_Lights {
PointLight pointLights[NUM_POINT_LIGHTS];
vec4 viewPos;
} scene;
const float PI = 3.14;
// Forward declarations
vec3 fresnelSchlick(float cosTheta, vec3 F0);
float DistributionGGX(vec3 N, vec3 H, float roughness);
float GeometrySchlickGGX(float NdotV, float roughness);
float GeometrySmith(vec3 N, vec3 V, vec3 L, float roughness);
void main() {
vec3 norm = normalize(fragNormal); // N
vec3 N = norm;
vec3 viewDir = normalize(vec3(scene.viewPos) - fragWorldPos); // V
vec3 V = viewDir;
vec3 F0 = vec3(0.04);
F0 = mix(F0, pbr.albedo, pbr.metallic);
vec3 Lo = vec3(0.0);
for (int i = 0; i < 4; ++i) {
vec3 lightVec = normalize(vec3(scene.pointLights[i].position) - fragWorldPos); // L
vec3 L = lightVec;
vec3 halfway = normalize(viewDir + lightVec); // H
vec3 H = halfway;
float distance = length(vec3(scene.pointLights[i].position) - fragWorldPos);
float attenuation = 1.0 / (distance * distance);
vec3 radiance = vec3(scene.pointLights[i].color) * attenuation;
// cook-torrance brdf
float NDF = DistributionGGX(norm, halfway, pbr.roughness);
float G = GeometrySmith(norm, viewDir, lightVec, pbr.roughness);
// vec3 F = fresnelSchlick(max(dot(halfway, viewDir), 0.0), F0);
vec3 F = fresnelSchlick(clamp(dot(H, V), 0.0, 1.0), F0);
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;
vec3 kS = F;
vec3 kD = vec3(1.0) - kS;
kD *= 1.0 - pbr.metallic;
// add to outgoing radiance Lo
float NdotL = max(dot(N, L), 0.0);
Lo += (kD * pbr.albedo / PI + specular) * radiance * NdotL;
// Lo += radiance;
}
vec3 ambient = vec3(0.03) * pbr.albedo * pbr.ao;
vec3 color = ambient + Lo; //ambient + Lo;
color = color / (color + vec3(1.0));
color = pow(color, vec3(1.0/2.2));
FragColor = vec4(color, 1.0);
// FragColor = vec4(scene.pointLights[0].position);
//FragColor = vec4(fragNormal, 1.0);
// FragColor = vec4(pbr.metallic, pbr.roughness, pbr.ao, 1.0);
// FragColor = scene.viewPos;
}
/* The below are from https://learnopengl.com/PBR/Lighting */
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;
}
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