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Blender material

Principled BSDF material

https://www.youtube.com/watch?v=_5dWa3z7bGw

  • Absorption:
  • Reflection:

  • Transmision:

  • Subsurface scattering

    • radius: how light scatters (
      • often is different for each color blue < green < red
    • inner color is the color of the material inside

  • Base layer

    • Diffuse/Subsurface base:

https://www.youtube.com/watch?v=DQeP363Xmn4

Principled because "physically based"... is too much used. Is a lightning model which generalizes many others.

BSDF: Bidirectional scattered distribution function. Bidirectional because include reflection and translucent effects.

Combines two models:

  • BRDF (Bidirectional reflactance dist. funct) Opaque surface (reflections)
  • BTDR (Bidirectional transmittance dist. funct) Transparent surface (refraction, translucency)

  • BSSDR (Bidirectional subsurface dist. funct) Transparent surface (refraction, translucency)

  • Reflactance: light that reflected from an object

  • Transmitance: light

  • Absorption: Light is turned into heat

  • Scattering: Light changes direction
    • Reflection: Light rebounds outside the material
    • Refraction: Light penetrates into the material changing direction because the difference on speed of light
      • Index of refraction is the ratio between speeds

Surface interactions:

  • Conductors (Metals):
    • Reflectivity high and depends on the wavelength (color)
    • Refracted light is quickly absorved
  • Dielectrics:
    • Reflectivity low and neutral (same for any wavelength)
    • Refracted light continues inside the material

Volume interactions:

  • Very high density: Diffuse material
  • High density: Subsurface scattering (like skin, rubber...)
  • Low density: Volumetrics (translucent)

Boundary interactions

Fresnel equation:

  • Which portion of the light gets reflected on entry (the rest is transmited)

    • Depends on the wavelength
    • Depends on polarization

  • Origen de la luz que nos llega de un punto de un material

    • Emision: El material emite luz
    • Especular: La luz rebota en el material, en el angulo preciso para una reflexi贸n directa
    • Reflexion: La luz de difumin

  • How to compute them?

    • Humans cannot detect polarization and phase shift, so ignore
    • Dielectric Fresnel:
      • Real IOR (ignore phase)
      • No wavelength dependency
    • Conductive Fresnel:
      • Complex IOR
      • Wavelength dependency
  • Aproximation Christopher Schlick
    • mix(F0, 1, (1-cos(angle))^5)
    • F0 can be computed by IOR
    • For metal misses on deep in reflectivity for
    • Enables linear combination of different F0's

  • Roughness

    • Not perfect reflectors
    • how problable is that the normal of the surface makes the ray face us

  • Energy conservation

    • Surfaces cannot reflect and transmit more energy than they receive.

  • Fine sheets:

    • Absorpsion and translucent

  • Sheen layer:

    • Simula pelusa
    • Normales son perpendiculares a

  • Clearcoat layer:

  • Microfaceted models: asume micro

  • Snell Law

    • Relates Incident and refracted angles to the index of refraction (and thus velocity of light in both media) but:
    • Says nothing about reflected (and
    • Says nothing about wavelength
    • Says nothing about polarization

  • Reflective light: How the light reacts above the surface

    • Color Base: Frecuencia que rechaza el objeto
    • Metalic: From dielectric to metalic
    • Specular:
    • Specular Tint:
    • Roughness: Variaci贸n de las normales

  • Subsurface Scattering (SSS): Difusion de la luz dentro del material (como la piel)

    • Subsurface: Factor de luz que entra
    • Subsurface Radious: Distancia media que se propaga la luz dentro del material
      • Se puede definir por separado para cada color primario
    • Subsurface Color: Color que hay por debajo de la superficie
    • Subsurface Index of Refraction
    • Subsurface Scale: Distancias que se aplican al radio
    • Subsurface Anisotropy: Direcci贸n de la difusi贸n

  • Diffuse: Reflected in all directions, proportional to the incoming light, independently of the angle of sight.

  • Specular: Reflected in mirrored normal direction

  • Subsurface: Color que hay por debajo de la superf铆cie

  • Metalic: 0 Dielectrico 1 Metalico
  • Specular:

  • Color

  • Emision:

    • Value: How much light emits
    • Color: Which color emits
  • Metalic:

Blender Unrealistic materials

  • Cell/Plane shaders: Plain colors gradient, used to make
  • Outline shaders: Add outline to contours
  • Screen tone shaders: Add pattern (malla) to generate shades
  • Painterfly shaders: Emulates brush strokes