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Introduction


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  • This lesson will take you through using the V-Ray HairMtl on hair in a Maya scene
  • This lesson topic is approximately 40 minutes in length
  • Lesson covers all 3 Learning Cycles for the Lesson Topic – Lecture, Demonstration, and Activity.
  • Learning Outcomes: You will be able to add, adjust, and manipulate a hair material for use in your scenes
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Contents


Overview
Available Materials
Lecture
Video Demonstration
Activity
Additional Resources

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Overview


Goal - We will apply coloring to a tail and mane to simulate a toy’s hair

Objective - To develop the look of a hair system           

Outcome - You will be able to create your own hair looks for characters as well as props and other objects


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Available materials


To set up the lesson follow the links below and download all available materials.

Lesson plan download
Presentation (Lecture) download
Demonstration tutorial download                 
Scenes & Assets download


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Lecture


1. Terminology

Hair is a complex element to recreate – it is multi-stranded with many layers of shades

  • Color
    • The color of hair is usually determined by not just it’s physical color, but also through it’s shine (specular) and translucence
    • Grades of color
  • Fur
    • Fur is shorter hair that usually covers animal skin
  • Length and type
    • The type of hair, it’s length, how it is styled all affect the look of hair

 

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2. Style


  • Hair shading can also apply to animal fur
  • Coarse vs. fine hair/fur
  • Wet vs. Dry
    • Wetness adds sheen that accentuates inherent colors in hair as well as specular reflections
    • Changes the character of fur and hair and how it clumps together

 

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3. Light and Hair


 

How hair is lit greatly affects how it’s color components come out

  • Front light
  • Back light
  • Density of hair and how much light occludes inside a clump of hair

 

 

4. VRayMtlHair3


а) Overview

Designed for rendering of hair and fur. Can be used to render geometry generated through the nHair, the VRayFur primitive, or other third party plugins. 
The material is composed of three components:

  • Primary specular - light that is reflected off the outer surface of a hair strand
  • Secondary specular - light that goes through the hair strand and is reflected off the back surface
  • Transmission component - Light that goes through a strand

 

 


b) Color Attributes

  • Overall Color – Adjusts all color components, like looking through a color filter
  • The darker it gets, the darker the overall hair
c) Diffuse Color and Amount
  • Defines the color of the hair in direct light
  • Amount controls how much of diffuse color comes through
  • 0 = no color; 1 = full color
d) Transparency
  • Defines the opacity of the hair strand
  • Black = Opaque; White = transparent
  • Higher transparency helps define how fine hair strands can be
  • Useful with gradient ramp and the VRayHairSampler texture node to create more transparency at tip of strand to feather the hair

 

 

e) Primary Specular
  • Defines the shine of the hair strand
  • Usually dark gray
f) Primary Amount
  • Multiplier for the Primary Spec color
  • Adjusts how much color comes out
g) Primary Glossiness
  • Defines the shine or sheen of hair
  • Values closer to 1 give the hair a sleeker, shinier look
  • Values closer to 0 give the hair a matte look, like a powdered wig
  • Default value is 0.8

h) Lock Secondary

  •   Sets the secondary spec color to be the same as the Transmission Color, since Secondary Spec is the color of light reflected off the back of a strand

 

i) Secondary Specular
  • Helps further define the shine color of the hair strand
  • Ignored if Lock Secondary is turned On

j) Secondary Amount

 

  • Multiplier for the Secondary Spec color

k) Secondary Glossiness

  • Further defines the shine or sheen of hair
  • Values closer to 1 give the hair a sleeker, shinier look
  • Values closer to 0 give the hair a matte look

l) Transmission

  • Color of light that passes through a strand
  • When Lock Secondary is Enabled, this color determines the hair’s color

n) Transmission Amount
  • Multiplier for how much Transmission color comes through

 

o) Transmission Glossiness Length
  • Defines the gloss along the length of the hair
  • Lower values (left image) make the highlight shorter along the strands than higher values (right image)

p) Transmission Glossiness Width

  • Defines the gloss across the width of the hair

 

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5. VRayMtlHair3 Options


a) Opaque Shadows
  • Forces the shadows to be made as if the strand is fully opaque
  • Speeds up rendering when hair is transparent

b) Opaque for GI
  • Treats the hair as opaque for GI calculations
  • Also speeds up rendering for transparent hair

c) Simplify for GI
  • Uses a simplified BRDF for GI calculations
  • May noticeably change the look, but speeds up rendering

d) Use Cached GI

  • Uses a map similar to Irradiance Map to calculate GI for the hair
  • When checked Off, calculates hair’s GI using Brute Force

 

 

6. Presets



 

7. Using GI


  • Using GI makes a big difference in the look of the hair (or fur), especially when it is supposed to be bright hair
  • GI helps fill in the hair where it does not receive direct light
  • The effect is less noticeable with darker hair

 

 

Conclusion



  • The Hair Material is useful for hair and fur
  • Look is controlled with Primary and Secondary Specular as well as Transmission of light
  • Glossiness of Spec defines sleekness of shine             
  • GI helps fill out darker areas of bright hair where direct light may not reach
 

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Demonstration



Time to see it work! 

Watch while I demonstrate how to setup a colorful hair shader for this toy pony.

 

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Activity



Time to do it yourself!

Use the provided  scene file to develop your own look for the pony’s hair.
We have also provided a final scene for your reference.


Used values:

а) Tail values

    • Tail Preset = Blonde (shiny)
    • Use VRayHairSampler texture node with a ramp to set color along the strand for the tail

 

 

 

 

b) Head values

  • Head Preset = Blonde (shiny)
  • Use the same VRayHairSampler texture node from the Tail with new Ramps to set head color along the strand as well as to randomize per strand color

 

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Additional resources


Find more training resources listed below: