CGCookie Core Materials Notes

Credits:

These notes are based off of the Core Tutorials on the CGCookie website. This is the Materials Core class.

Instructor: Ewa Wierbik-Ziąbka

Notes:

The instructor includes a number of downloaded .blend files. I haven’t checked them all out, but several of them seem to go well beyond the basics covered in the course and they’re definitely worth checking out to see how she achieved some of the effects.

Simple Shaders

Glossy BSDF

  • Creates glossy or metalic surfaces
  • Roughness
    • A roughness 0 creates a perfectly reflective surface
  • Anisotropy
    • 0 is no anisotropy
    • Negative values elongate values along tangent
    • Positive values elongate along normal tangent
  • Rotation
    • 0 is no rotation
    • 1 is 360 rotation

Diffuse Shader

  • Only has roughness slider(Fresnel)
  • Light bounces in random directions

Emission

  • Emits light
  • Can adjust color and strength
  • Can create whole objects that light up, like Neon, or a glowing Suzanne head
  • When strength is set very high, the light will appear white, while reflections will show the color of the light

Transparent

  • Pure white and the object can be completely transparent
  • The darker the color, the less transparent the object is

Holdout shader

  • The object is not very transparent, but it asks like a mask
  • Great for compositing
  • If you change the scene background to transparent, it will create an alpha where the object is

Mix shader

  • Diffuse and Glossy are a typical combination
  • Except for metal, the color for glossy should typically be white
  • Diffuse is where you set the color, and get a plastic like material
  • Factor controls which shader has a larger effect
    • 0 for Slot A and 1 for Slot B

Layer weight

  • This is not a shader, but an Input
  • Plug Fresnel or Facing into the mix shader factor
  • Fresnel
    • Dependent between normal and viewing angle
  • Facing
    • Blends between first and second shader based on viewing angle

Add shader

  • If you add two glossy shaders you may end up with reflections that are stronger than the source light
    • This is not accurate
    • This will look strange
  • This is mostly used for emission or volume shaders
  • It is also used to add diffuse and glossy for ceramics

Refraction Shader

  • Alone you get dark results near the edges - it almost looks like a toon shader
  • Refraction is often mixed with glossy
    • The sharpness of the refractions is controlled by the roughness of the glossy
    • The amount of light that passes through the object is controlled by the roughness of the refraction shader
    • Color is usually controlled by the refraction shader
  • The glass shader may be more realistic than this combination

Translucent

  • Created for thin objects like leaves or paper
  • Often mixed with diffuse
    • With diffuse as the first shader, generally make .5 the maximum mix factor
    • Changing the color is often done on both shaders

Subsurface Scattering

  • Works best on thicker objects
  • Attempts to mimic light passing through skin
    • To best mimic this, choose Random Walk(Skin)
  • Scale controls how much light passes through the object
  • Radius controls the which of RGB travels the most through the object

Volume Scatter

  • If an object is thick and detailed, subsurf may not look right
  • Plug into volume socket on material output, not surface
  • If the value is pushed to something high, maybe starting at 20 or so, it appears solid instead of smokey
  • The object may be dark
    • On the rendering tab Light Paths->Max Bounces->Volume may need to be increased. Try 3
    • Negative anisotropy may make object brighter too
  • Use an add shader with volume absorption and move volume absorption density to 10+ to change color

Volume Absorption

  • Often used for colored glass
  • Use glass shader in Surface slot, Volume Absorption in first slot of add shader, and Volume Scatter in second slot for colored glass
  • Volume absorption and scatter can be used to create clouds, but it needs to be mixed with something that controls the density to get something that looks like clouds. I’ll have to check out the included course files to see how that effect was achieved.

Ray Portal BSDF

  • Create Portal Game like portals, security camera monitors, etc.
    • Security Camera Monitor
    • Note to Self: There ought to be a way to select an object and automatically get the needed attributes from it. Not sure if that’s a driver, plugin, or what, but it should be doable.
    • Note the 2nd: the instructor mentions Geometry nodes. Checkout the downloaded class files to see if there’s a more detailed layout that already does this