Shading

Flax implements Physically-Based Rendering with BRDF shading that tries to realistically simulate how light reacts with object surfaces and bounces off.

Standard Shading

Material diffuse and specular colors are computed based on material properties as follows:

diffuseColor = materialColor * (1 - materialMetalness)
dielectricF0 = 0.16 * materialSpecular^2;
specularColor = lerp(dielectricF0, color, materialMetalness)

Default shading formula calculates lighting as follows:

diffuseLight = Diffuse_Lambert(diffuseColor);
F = F_Schlick(specularColor, VoH);
D = D_GGX(roughnessSq, NoH) * energy;
Vis = V_SmithJointApprox(roughnessSq, NoV, NoL);
specularLight = (D * Vis) * F;

GBuffer

GBuffer is a set of render target images used to capture common material properties such as color, metalness, roughness, and surface normals to calculate per-pixel lighting as a deferred lighting pass. This technique is commonly used in rendering as it decouples shading/shadowing complexity from materials rendering stage.

GBuffer layout:

* GBuffer0: [RGB] Color, [A] AO
* GBuffer1: [RGB] Normal, [A] ShadingModel
* GBuffer2: [R] Roughness, [G] Metalness, [B] Specular, [A] UNUSED
* GBuffer3: [RGBA] Custom Data (per shading mode)