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titleIridescence Parameters

Iridescence

Iridescence is a view-dependent scattering of light that causes a color shift. This is the same effect responsible for the color swirl on a soap bubble, peacock feathers, or a shiny beetle. "Holographic" or color shifting paint uses this effect as well.

Iridescence Mode

Select which iridescence mode to use: Artistic or Physical.

In Artistic mode, we just set 2 colors. Depending on the iridescence scale factor, we will see N number of "rainbows". The default of red and blue is appropriate to get a maximum color spread but you can reduce the number of colors rendered by changing these defaults. Unless otherwise specified or demonstrating an Artistic Parameter, the examples use Physical mode.

In Physical mode, we pass the thickness of your thin film in nanometers. The iridescence effect happens when the physical thickness is close to the visible spectrum. You can start around 800nm and increase the value to see the effect. This option is great because it reduces parameters to tweak at the cost of flexibility. Unless otherwise specified or demonstrating an Artistic Parameter, the examples use Physical mode. Below are Artistic (left) and Physical (right) modes.

 

 

Face Gain

Iridescence gain at facing angle (0 degree incidence).

 

 

Edge Gain

Iridescence gain at the glancing angle (90 degree incidence). For Edge Gain to work, you need a small amount of Face Gain to activate it.

 

 

Primary Color

This is for Artistic mode only.

Iridescence primary color on the hue wheel to start from. From here the color shifts through the other available hues between the Primary and Secondary Color. The closer on the color wheel your choices, the fewer colors will be rendered. Below are three examples beginning at Red, then Yellow, and finally Green. The color bar shows what colors are available between these choices.

 

 

Secondary Color

This is for Artistic mode only.

Iridescence secondary color on the hue wheel to end. As demonstrated above you can use this to limit the colors rendered. Below are three examples where the Secondary Color goes from Violet to Blue and finally to Green. The hue bar shows this change on a ramp.


Falloff Speed

This is for Artistic mode only.

Falloff speed from Primary Color to Secondary Color. Larger numbers falloff more slowly. Below uses the defaults for Artistic Mode but we change the Falloff Speed from 0.1 to 0.5 to 1.0

 

 

Falloff Scale

This is for Artistic mode only.

This sets how many times the iridescence "rainbows" color repeat. Below we go from 0.5 to 1.0 and finally 3.0. Notice that higher values begin to repeat the rainbow effect. This is useful for simulating oil patterns such as oil on water or soap bubbles.

 

 

Flip Hue Direction

This is for Artistic mode only.

Flip the hue wheel direction between primary and secondary colors. By default, the hue wheel direction is counter clockwise. Left is off, right is on.

 

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Thin Film Thickness

This is for Physical mode only.

Thin film thickness in nanometers. We begin at 400 then 800 and finally 1600 nanometers from left to right. Notice that at 1600 we begin to see a repetition in the rainbow effect. This is similar to the effect of using the Falloff Scale in Artistic Mode.

 

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Roughness

Iridescence roughness, this is like other roughness parameters where you can go from a mirror-like reflection at 0.0 to diffuse reflection at 1.0. Below are examples, left to right, of 0.0, 0.5, and 1.0. Softer looks are reminiscent of color changing makeup and similar powders.

 

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Double Sided

If on, illuminate on both sides of the surface for this iridescence lobe. This is useful for thin opened surface surfaces such as feather feathers and leaves that are modeled without thickness.

  

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titleFuzz Parameters

Fuzz Parameters

This parameter introduces a bit of retroreflection and helps simulate fabrics, fuzz, and fine powder.

Gain

Fuzz weight. Higher numbers increase this effect.

 

 

Color

Fuzz color. This simulates a soft velvety-like effect. This is applied "on top" of the previous Specular lobes and may resemble dirt or fine dust.

 

 

Cone Angle

Fuzz roughness (corresponding to Marschner R cone angle). Higher numbers increase the effect at facing angles.

 

 

Bump

Normal to use for the fuzz illumination. If this is not set, it will use the global bump normal specified in the Properties near the bottom of this page.

 

 

Double Sided

If on, illuminate on both sides of the surface for this fuzz lobe, that is, this will illuminate the surface whose normal is pointing away from the camera as well.

 

 

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titleSubsurface Scattering Parameters

Subsurface Scattering Parameters

Subsurface Model

Select a subsurface scattering model: Jensen Dipole, DEon Better Dipole, Burley Normalized - This is the preferred method, and Multiple Mean Free Paths

Burley Normalized produces the most accurate effect while preserving details.

Jenson and DEon Dipoles are great for very translucent objects like gummies.

Multiple Mean Free Paths is great for texturing to produce color bleed easily. While not necessarily physically correct, its intuitive scattering of textured colors works well for art direction.

 

 

Gain

Subsurface scattering weight. Higher numbers increase the visibility of the subsurface scattering.

 

 

Color

Subsurface scattering color.

 

 

Mean Free Path Distance

Subsurface scattering mean free path scalar distance. This specifies how far the light travels inside an object and as a consequence how smooth the subsurface scattering is. This gets multiplied by the unit length set in the Properties section. Higher amounts make the object appear less opaque and more translucent.

 

 

Mean Free Path Color

How far the light travels in the R, G, and B spectra. This is scaled by Mean Free Path Distance. Different colors may spread more or less and provide interesting effects like the red color bleeding into shadow edges on skin.

 

 

Post Tint

Tint that is applied at the end of the subsurface computation. If we want to apply the tint before the subsurface computation, set Irradiance Tint in the Properties section.

 

 

Short Gain

Short subsurface gain or weight. This is only valid for Multiple Mean Free Paths subsurface model.

 

Short Color

Short subsurface color. This is only valid for Multiple Mean Free Paths subsurface model.

 

 

Short MFP Distance

Short subsurface mean free path scalar distance.

 

 

Long Gain

Long subsurface gain or weight. This is only valid for Multiple Mean Free Paths subsurface model.

 

 

Long Color

Long subsurface color. This is only valid for Multiple Mean Free Paths subsurface model.

 

 

Long MFP Distance

Short subsurface mean free path scalar distance.

 

 

Diffuse Computation Switch

Switch the subsurface computation to a diffuse computation if the dmfp is smaller than the ray footprint. This is an optimization to ignore computing scattering, especially on far away objects.

 

 

Double Sided

If on, illuminate on both sides of the surface for this subsurface lobe, that is, this will illuminate the surface whose normal is pointing away from the camera as well.

 

 

Trace Control:

Consider Backside

Whether subsurface respects surfaces on the other side. This is for the hit side, not the illuminating side (which is subsurfaceDoubleSided):

  • "Off" - It will ignore surfaces on the other side completely. This is useful to make objects appear thicker than they are.
  • "On" - Normal mode, where the diffusion happens between the front and the first surface behind it.

 

 

Continuation Ray Mode

Control continuation ray mode:

"Off" - Simply trace out of the object (default).

"Last Hit" - Ignore internal geometry and jump to the last surface.

"All Hits" - Scatter (collect light) on all hits as the ray leaves the object. This can bring additional brightness, at the cost of additional noise.

 

 

Max Continuation Hits

Maximum number of hits to test in all hits mode. This is only valid when Continuation Ray Mode equals All Hits

 

 

Follow Topology

Controls how strongly normals are considered in the subsurface computation. This may affect visible details created through bump mapping as well.

 

 

Trace Subset

Specify trace subset for inclusion/exclusion when struck by a ray indirectly.

 

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