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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 insect. "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".

 

 

In Physical mode, we pass the thickness of your thin film in nanometer. 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.

 

 

Face Gain

Iridescence gain at facing angle (0 degree incidence).

 

 

Edge Gain

Iridescence gain at the glancing angle (90 degree incidence).

 

 

Primary Color

This is for Artistic mode only.

Iridescence primary color on the hue wheel to start from.

 

 

Secondary Color

This is for Artistic mode only.

Iridescence secondary color on the hue wheel to end at.

 

 

Falloff Speed

This is for Artistic mode only.

Falloff speed from Primary Color to Secondary Color. Larger numbers falloff more slowly.

 

 

Falloff Scale

This is for Artistic mode only.

This sets how many times the iridescence "rainbows" color repeat.

 

 

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.

 

 

Thin Film Thickness

This is for Physical mode only.

Thin film thickness in nanometernanometers.

 

 

Roughness

Iridescence roughness

 

 

Double Sided

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

 

 

Fuzz Parameters

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

Gain

Fuzz gain.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 belownear 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.

 

 

Subsurface Scattering Parameters

Subsurface Model

Select a subsurface scattering model: Jensen Dipole (0), DEon Better Dipole (3), Burley Normalized (1) - 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 (2)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 gain.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 solidopaque 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).

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

"AllHitsAll Hits" - Scatter (collect light) on all hits as the ray leaves theobjectthe 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.

 

Single Scattering Parameters

Single scatter is a simple and inexpensive effect for scattering effects.

 

 

Gain

Single scatter gain or weight.

 

 

Color

Single scatter color.

 

 

Mean Free Path

Single scattering mean free path scalar distance. This specifies how far the light travels inside an object and as a consequence how smooth the single scattering is. This gets multiplied by the unit length set in the Properties section. Larger values are more translucent.

 

 

Mean Free Path Color

How far the light travels in the R, G and ,  and B spectra. This is scaled by Mean Free Path Distance.

 

 

Directionality

Single scatter directionality:

1: forward scatter which is more light on the backside.

-1: backward scatter which is more light on the front side.

0:isotropic (no effect).

 

 

Refractive Index

Single scatter index of refraction.

 

 

Blur

Blur strength for single scatter.

 

 

Backside Direct Illum Gain

Gain for direct illumination from the other side.

 

 

Direction Tint

Tinting color for the Backside Direct Illum Gain.

 

 

Double Sided

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

 

 

Trace Control Parameters:

Consider Backside

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

  • "Off" - It will ignore surfaces on the other side completely. This is useful to make objects apear 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

 

 

Direct Gain Mode

Control continuation ray mode:

"First Hit" - Simply trace to the next surface (this is tied to considerBackside).

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

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

 

 

Trace Subset

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

 

 

Glow Parameters

Glow can make an object appear to emit light. This is useful when you need a textured effect like lit panels, circuitry, or other complex effects with local influence in lighting.

 

 

Gain

Glow gain or weight.

 

 

Color

Controls the incandescence color, or glow, of the material.

 

 

Reflection/Refraction Parameters

Refraction Gain

Refraction gain.

Reflection Gain

Reflection gain.

Refracton Color

Refraction color.

Roughness

Refraction and reflection roughness.

Refractive Index

Index of refraction.

Thin

If on, correctly split energy according to Refractive Index between reflection and refraction, but do not bend the ray in refraction (simulating a double pane of glass with a single pane).

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