The biggest part of the programme is the laws governing the rendering system.
The scene uses PBR or Physically Based Rendering.
The aim is to simulate the behaviour of light on objects and their surfaces as realistically as possible.
Objects have given textures to represent their behaviour when exposed to light.
Roughness: the higher this value, the more light is diffused in multiple directions. A low value corresponds to a smooth surface.
Metalic: the higher the value, the more the object will reflect light.
AO: to simulate object shadows in certain hollows
As seen above, the AO adds a depth effect to the object itself.
You can experiment on these three concepts on the flower in my scene by tweaking the values.
Roughness visual proprieties
Metalic visual proprieties
PBR also includes the principle of energy conservation.
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// material properties
vec3 albedo = texture(gAlbedo, TexCoords).rgb;
float metallic = texture(gPosition, TexCoords).a;
float roughness = texture(gNormal, TexCoords).a;
float ao = texture(gAlbedo, TexCoords).a;
float ssao = texture(SSAOMap, TexCoords).r;
float combined_ao = ssao * ao;
// input lighting data
vec3 N = mat3(inverseViewMatrix) * texture(gNormal, TexCoords).rgb; ;
vec3 V = normalize(camPos - WorldPos);
vec3 R = reflect(-V, N);
// calculate reflectance at normal incidence;
vec3 F0 = vec3(0.04);
F0 = mix(F0, albedo, metallic);
// reflectance equation
vec3 Lo = vec3(0.0);
// calculate per-light radiance
vec3 L = normalize(-directionalLightDirection);
vec3 H = normalize(V + L);
//float distance = length(lightPositions[i] - WorldPos);
//float attenuation = 1.0 / (distance * distance);
vec3 radiance = directionalLightColor;
// 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 numerator = NDF * G * F;
float denominator = 4.0 * max(dot(N, V), 0.0) * max(dot(N, L), 0.0) + 0.0001;
vec3 kS = F;
vec3 kD = vec3(1.0) - kS;
kD *= 1.0 - metallic;
float NdotL = max(dot(N, L), 0.0);
...
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